BIOLOGY REVISION AND EXAMINATION TIPS Main reasons why Students Perform Poorly in the Biology Subject  Confusion of biology concepts and terminologies.  Inability to recall ideas about the subject content (subject matter). This could be attributed to lack of interest and concentration in class and poor study habits hence the meaning of the content is never grasped.  Use of poor vocabulary-lack of good English command to express ideas e.g. the relaxation of erector pili muscles cause the hair to fall down instead of lie flat on the skin surface  Assuming too much. This leads to giving sketchy, ambiguous, half answers or giving more information than asked which in most cases is irrelevant.  Not following simple instructions and guidelines in answering questions (examination techniques) particularly graphical and structured questions. Students need to know that most structured questions require a deeper understanding of the concepts behind the question/experiment. Furthermore, most of the answers in the various subsections are tied i.e. the student has to get the first part of the question right first to guarantee him/her a correct response in the subsequent subsections of the question. Possible Remedies  During study sessions, ensure that you understand adequately the subject matter for every topic. This calls for a lot of reasoning, comparison, application, relation, evaluation, analysis and observation. These are core science-process skills that make science therefore Biology a unique discipline. Understanding can be enhanced through having interest in what you are reading (have a positive attitude towards the subject having understood its relevance in your future career as well as individual life and community development); planning and organizing yourself by knowing what to do, where, when and for how long (prepare a realistic study schedule/timetable and follow it); concentrate by being attentive and alert in class; be determined; never give up and have a dream or vision that will help you look into your future. Thorough revision or study ensures information is securely fixed in the long-term memory of the brain (principle of consolidation). The best method is ensuring you review notes right after class. Large chunks of information can be summarized through use of pseudo codes, mnemonics or use of concept maps (schematic mapping).  Arrive in class and examination room in time. This will enable you gather all the verbal and written concepts taught and boost confidence and reduce pre-exam stress respectively.


Large chunks of information can be summarized through use of pseudo codes, mnemonics or use of concept maps (schematic mapping).  Arrive in class and examination room in time. This will enable you gather all the verbal and written concepts taught and boost confidence and reduce pre-exam stress respectively. This can also be enhanced by conferring with other students to predict what might be in the test prior to the start of the examination.  Read through each question at least three times before you decide to write down your answer. Use grammatical clues within a statement as hints for the correct answer. Underline the key words in the question to help you know exactly what is being asked. If you go blank on any of the questions, skip it and go to the next but remember to spare some time later to answer the skipped question (s).  Believe in yourself. Do not try to be perfect; instead try to balance your work by giving the best. Never be in a hurry/panic. The time allocated for each paper has been pretested to be adequate for every student’s level of achievement (intelligence) and it only requires proper planning and approach to fit within the allocated time and even have time to review your work. Budget your time according to what is required of you in each question. Answer questions in a strategic order starting with the easy ones to help you build confidence and familiarize yourself with the vocabulary and concepts that you will deal with, then answer the more difficult questions.  Write your answers neatly, accurately and precisely. Start by writing the points you are sure of first. This is because in Biology, only the first required correct responses are awarded. Any extra point beyond the required is just acknowledged but not awarded even if it is also or is the only correct one yet the earlier stated ones are wrong or not all.  Use proper English and avoid confusing concepts. English is the medium of instruction (lingua franca) of the Biology subject matter and therefore a correct and clear command of the language is paramount to passing the subject.  Remember to write exhaustive answers as half answers and ‘hanging’ statements are never awarded in any Biology examination e.g. for each structure or process, mention the function or reasons respectively depending on how the question is framed.  Concentrate on the unique or distinguishing features or characteristics and avoid obvious things e.g.


 Remember to write exhaustive answers as half answers and ‘hanging’ statements are never awarded in any Biology examination e.g. for each structure or process, mention the function or reasons respectively depending on how the question is framed.  Concentrate on the unique or distinguishing features or characteristics and avoid obvious things e.g. if asked for the adaptations of the gills in fish to gaseous exchange, don’t expect to be awarded for mentioning that they are moist yet it is obvious that fish are aquatic animals found in water (moist) bodies.  Strive to answer the questions as they are stated but not to memorize the content read e.g. you might be tempted to state all the adaptations of gaseous exchange structures you know including the structures having a dense network of capillaries…yet the question asked is specifically asking for the adaptations of plant structures. Therefore, get to understand the question asked first before attempting to answer.  Avoid canceling your work by being sure before writing down. Canceling can also be a point of suspicion for cheating. Neatness of the answers also encourages the examiner and implies keenness, clarity and being sure, all being the expected attributes of a modern scientist.  Write all scientific names and technical words/phrases according to the rules of the binomial nomenclature and correct spellings respectively. Avoid using abbreviations, short codes and symbols as most are not conventional (not universally used/accepted by the body of scientists) hence you risk being penalized for their use.  Never add information in brackets if you are not sure e.g. red blood cells (leucocytes). This will not be awarded as it shows confusion of concepts which is penalized.  All diagrams drawn should be clear, neat and proportional sketches (not artistic impressions) and must be true representations of the object/specimen. Follow the simple rules: Labeling lines should not cross each other; the labeling line should touch the structure in question but not hang; use lines not arrows to label, arrows only show direction; do not shade the drawings but use dots or crosses within the part if you want to show the difference; lines must be continuous and not broken; no two structures should have the same name; for cross-sections and plan diagrams, remember to use double outer lines (outline) and only show key/few features avoiding unnecessary details.


This will not be awarded as it shows confusion of concepts which is penalized.  All diagrams drawn should be clear, neat and proportional sketches (not artistic impressions) and must be true representations of the object/specimen. Follow the simple rules: Labeling lines should not cross each other; the labeling line should touch the structure in question but not hang; use lines not arrows to label, arrows only show direction; do not shade the drawings but use dots or crosses within the part if you want to show the difference; lines must be continuous and not broken; no two structures should have the same name; for cross-sections and plan diagrams, remember to use double outer lines (outline) and only show key/few features avoiding unnecessary details.  For essay questions, choose the option you are sure of and comfortable with in terms of raising the maximum points possible. Write down key words as they are fresh in your mind; use the first paragraph as an overview of your essay; when time is up for one question or part of the question, stop writing, leave some space and begin the next question or part of the question. The incomplete answers can be completed later during review. However, remember six incomplete answers will receive more credit (marks) than thee complete ones, so don’t waste time. Compactness, completeness (exhaustiveness) and clarity of a well-organized answer is what is important in essay questions. This can be achieved by ensuring that every sentence earns you at least 2 marks hence a 1-1½ pagelength (A-4 paper/foolscap) essay is more appealing than 3 pages of verbal irrelevancies. Remember also that to know a little and present it well is superior to knowing much and presenting it poorly.  Allow yourself time to review your work. Review allows you to ensure that you have answered all the required questions, not skipped any relevant question, not made some simple mistakes and also gives you time to complete any uncompleted questions as well as correcting the wrongly answered ones.


Remember also that to know a little and present it well is superior to knowing much and presenting it poorly.  Allow yourself time to review your work. Review allows you to ensure that you have answered all the required questions, not skipped any relevant question, not made some simple mistakes and also gives you time to complete any uncompleted questions as well as correcting the wrongly answered ones.  Rules for graphical questions may vary from time to time (year to year) but currently the following apply: Use a thin (well-sharpened) pencil to draw thin clear curves for accuracy; all graphs should be curves drawn using continuous lines regardless of the number; the graph should occupy at least ¾ of the grid/graph paper provided, achieved through appropriate scales; state the title and scale at the top of the graph clearly and avoid using abbreviations (remember to include the given units); ensure the Cartesian plane (X and Y axes) has arrows at the ends to show continuity; use dots/small crosses for plotting; do not extrapolate the curve unless asked for a point beyond the plotted ones; label the axes and curves; be neat; if the range of the data is so wide, break the affected axis/axes but don’t force the curve to begin from the 0 point. Commonly Used First Statements in Biology Questions and their Meanings  State/What -This requires the student to present the said concept in a brief and clear form. If it is an adaptation, then it must be given fully i.e. structure, modification and function.  Explain- Give reasons why something/anything happened or will happen.  Describe-Give a detailed or graphic account of the issue or phenomenon showing all features and characteristics e.g. if it is a structure and function question (adaptation), you are expected to correctly name the structure or feature, explain how it is modified and give the function (s) of the structure. Sketchy explanations are penalized or earn least marks. So give as many detailed points as possible.  Define-Give a precise meaning of a word/phrase normally in one sentence.  Illustrate-Use a figure, diagram or any non-text form as an example to explain or make something.  Name/Give/Mention-Give points only, no explanations  Why-Give clear reasons supported by an argument.  Outline-Give the main features in a sequential manner.


 Illustrate-Use a figure, diagram or any non-text form as an example to explain or make something.

 Name/Give/Mention-Give points only, no explanations  Why-Give clear reasons supported by an argument.

 Outline-Give the main features in a sequential manner.

 Distinguish between-Define the terms to clearly bring out the differences in their meanings.

You only earn a full point (s) or mark (s) when both definitions are correctly given.

 Account for-Such questions need a two-prong approach: The first part is to give the trend/situation as it is e.g.

the volume increases (d) rapidly/gradually with increase in temperature.

The second portion of the answer involves giving the explanation/reasons for the situation/trend e.g.

because the molecules/particles gain kinetic energy, moving/vibrating more rapidly hence occupying more space (hence raising the volume).

These questions are common in the Paper 2; Section A structured questions and the compulsory question in Section B of the same paper.

The questions assume prior knowledge in either one or a number of the Biology topics.

 Differentiate/Give the differences-Use either a table for the differences or use connectors such as the word ‘while’.

Make sure the responses rhyme to earn a mark e.g.

an artery has a narrow lumen while the capillary has a wide lumen not an artery has a narrow lumen while a capillary’s wall is thin.

 Compare (and Contrast)-Outline both the similarities and differences between the given terms/processes.


FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE.


FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge".


FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge". It is the study of living things/organisms.


FORM ONE BIOLOGY
By the end of form one work, the learner should be able to:
Define Biology
List the branches of Biology
Explain the importance of Biology
State and explain some of the characteristics of organisms
State and explain some of the general characteristics of organisms
Explain the external features of plants and animals
Write down the difference between plants and animals
Define classification
Use the magnifying lens to observe the external features of plants/ animals
Record observations of the main external features of plant leaf form
Draw different types of leaf forms
Observe, record and draw the main external features of plants
Observe ,record and draw the main external features of animals
State the necessity and significance of classification
Name the major units of classification
Name the five kingdoms of living things
List the taxonomic units in plant and animal kingdoms
Classify maize and human beings
Define Binomial nomenclature
State the principles of Binomial nomenclature In naming organisms
Use collecting nets, cutting instructions instruments and hand lens
Preserve collected specimen
Observe and group collected and preserved specimen according to their similarities
Define a cell
Draw and label the light microscope
Identify parts of the light microscope and state their functions
Describe how to care for a light microscope
Describe how a light microscope is used
Draw and label plant and animal cells as seen under a light microscope
Calculate the magnification of objects as seen under a light microscope
Observe a prepared slide under a light microscope
Prepare temporary slide of onion epidermis and observe it under a light microscope
Draw and label plant and animal cells as seen under electron microscope
Describe the structure and function of the cell
Cell wall
Cell membrane
Cytoplasm
Describe the structure and function of the cell organelles
Estimate the size of a cell as seen in the field of view of a microscope
Write down the differences between plants and animal cells
Write down similarities between plant and animal cells
List down specialized plant and animal cells
State the modifications and functions of specialized cells
Define tissues, organs and organ systems
Give examples of tissues organs and organ systems
Define the term cell physiology
Describe the structure and properties of cell membrane
Define diffusion
Carry out experiments to demonstrate
diffusion in liquids
diffusion in gasses
Explain the factors affecting diffusion
Explain the role of diffusion in living things
Define osmosis
Describe movement of water molecules across semi-permeable membrane
define and describe the terms used in the study of osmosis such as:
Osmotic pressure
Osmotic potential
Isotonic solution
Hypertonic solution
Hypotonic solution
Turgor pressure
Hemolysis
Wall pressure
Plasmolysis
Deplasmolysis
carry out an experiment on selective permeability of membrane
State factors affecting osmosis
Explain the role of osmosis in organisms
Explain the factors affecting osmosis
Describe what happens when a plant cell is placed in a hypertonic, hypotonic or isotonic solution
Carry out an experiment to show plasmolysis in epidermal cells of an onion bulb
Describe osmosis of animal cells in a hypertonic solution
List down factors affecting active transport
Define active transport
Define the role of active transport in living things
Define nutrition
Write down the importance of nutrition
List down the modes of feeding in organisms
Draw and label the external structure of a leaf
Draw and label the internal structure of the leaf
Name the parts of a leaf
State the functions of the parts of a leaf
Define photosynthesis
Draw and label the chloroplast
Describe the process of photosynthesis
List down the importance of photosynthesis
Explain some of the factors influencing photosynthesis
Explain the factors affecting photosynthesis
Explain how the leaf is adapted to the process of photosynthesis
Test the presence of starch in a green leaf
Investigate whether chlorophyll is necessary for photosynthesis
Investigate whether light is necessary for photosynthesis
carry out an experiment to investigate whether
Carbon (IV) oxide is necessary for photosynthesis
Oxygen is produced during photosynthesis
Define Chemicals of life
List down types of carbohydrates
Write down properties and functions of monosaccharaides
Define disaccharides
List properties and functions of disaccharides
Define hydrolysis and condensation
Define polysaccharides and lipids
Write down the properties of polysaccharides and lipids
carry out tests on
Starch
Reducing sugars
Non-reducing sugar
Lipids
Proteins
Vitamin c
Write down the properties and functions of proteins
Distinguish between carbohydrates, proteins and lipids
Define enzymes
Write down the properties and functions of enzymes
Know the naming of the enzymes and their substrates
Explain the importance of enzymes
carry out an experiment on
Effect of temperature on enzymes
Effects of enzyme concentration on the rate of a reaction
Effect of PH on enzyme activities
Define hetetrophism
List down the different modes of heterotrophism and describe them
Define dentition
Draw and label different types of teeth
Describe the structure of a tooth
Identify different types of teeth
Describe the adaptations of the teeth to their functions
Define dental formulae
Describe and write down the dental formulae of herbivore carnivore and omnivore
Write down the definition of herbivores, carnivores and omnivores
Explain the adaptations of dental formulae in various groups of animals, to their mode of feeding
Draw and label the internal structure of different types of teeth
Write down the functions of the different parts of the internal structure of teeth
Name and discuss common dental diseases
Write down the adaptations of herbivores to their mode of feeding
Write down the adaptations of carnivores to their modes of feeding
Identify various organs associated with the digestive system of a rabbit
Draw and label parts of the human digestive system
Describe the regions of the alimentary canal of human digestive system
Explain the functions of the human digestive system
Describe the various regions of the human alimentary canal and their functions
Describe how the ileum is adapted to its function
Analyze the food content in the alimentary canal of a herbivore
Carry out an experiment on the breakdown of starch by diastase enzymes
Describe how the ileum is farther adapted to its functions
Explain the end products of the digestion of various food
Explain the function of the colon
Explain the process of assimilation of food substances
Write down the summary of chemical digestion in alimentary canal
Write down the importance of vitamins in human nutrition
Write down the sources of vitamins
State deficiency diseases of various vitamins
Write down the importance of mineral salts in human nutrition
State the source of mineral salts
State the deficiency diseases of mineral salts
Write down the role of roughage in nutrition
Write down the role of water in nutrition
Discuss factors which determine energy requirements in human beings
Participate in group discussions and present findings on factors that determine energy requirements in human beings
Introduction To Biology
Biology derived from Greek words-BIOS meaning LIFE and LOGOS meaning STUDY or KNOWLEDGE. Biology means "life knowledge". It is the study of living things/organisms. Branches of Biology
Botany - study of plants.


Biology means "life knowledge". It is the study of living things/organisms. Branches of Biology
Botany - study of plants. Zoology - study of animals. Microbiology - study' of microscopic organisms. Morphology - study of external structure of organisms. Anatomy - study of internal structure of organisms. Physiology - study of the functioning or working of the cells or body. Biochemistry - study of the chemistry of materials in living organisms. Cytology - study of cells. Genetics - study of inheritance. Ecology- study of the relationship between organisms and their environment. Taxonomy - sorting out of organisms into groups. Histology - study of fine structure of tissues. Virology - study of viruses. Bacteriology - study of bacteria. Entomology - study of insects. Ichthyology - study of fish. Importance of Biology
One learns about the functioning of the human body. One understands the developmental changes that take place in the body. It contributes immensely to improved life. It enables one to enter careers such as:
Medicine,
Nutrition,
Public Health,
Dentistry,
Agriculture
Environmental Studies. Teaching
Characteristics of Living Things
Life defined through observations of activities carried out by living things;
Nutrition –
Nutrition is the processes by which food/nutrients are acquired/made and utilized by living organisms. Green plants and certain bacteria make their own food. All other organisms feed on complex organic materials. Respiration –
This is the breakdown of food to provide energy. The energy released is used for various activities in the organism. Gaseous Exchange –Process throw which respiratory gases(CO2&O2) are taken in and out through a respiratory surface. Excretion –
Excretion is the removal of metabolic wastes from the body. Substances like urea, carbon dioxide (Carbon (IV) oxide). These substances are poisonous if allowed to accumulate in the body. Growth and Development –
Growth means irreversible change in size. All organisms increase in size that is, they grow. Development is irreversible change in complexity. As they do so, they also become differentiated in form. Reproduction-Reproduction is the formation of new individuals of a species to ensure continued existence of a species and growth of its population. Irritability –
The ability of organisms to detect and respond to changes in the environment. This is of great survival value to the organism.


Reproduction-Reproduction is the formation of new individuals of a species to ensure continued existence of a species and growth of its population. Irritability –
The ability of organisms to detect and respond to changes in the environment. This is of great survival value to the organism. Movement –
Is the progressive change in position from one place to another. Some organisms are sessile (i.e. fixed to the substratum). The majority of plants move only certain parts. Collection and Observation of Organisms
Biology as a practical subject is learnt through humane handling of organisms. Materials needed for collection of organisms:-
Knives to cut portions of plant stem/root or uproot. Polythene bags to put the collected plant or specimens. Insect collecting jars. Insect killing jars. Hand gloves. Sweep nets
Pooters
Traps
Observation of Organisms
Observe the plant/animal in its natural habitat before collecting. Identify the exact place -on surface, under rock, on tree trunk, on branches. What does it feed on? How does it interact with other animals and the environment? How many of that kind of plant or animal are in a particular place? Plant specimens placed on the bench and sorted out into;- seeds/stems/roots/leaves/fruits. Animal specimens may be left inside polythene bags if transparent. Others (killed ones) are put in petri dishes. Use hand lens to observe the external features of small animals. Presenting the Results of Observations
Organisms are observed and important features noted down: colour, texture hard or soft; if hairy or not. Size is measured or estimated. Biological Drawings - It is necessary to draw some of the organisms. In making a biological drawing, magnification (enlargement) is noted. Indicate the magnification of your drawing. i.e how many times the drawing is larger/smaller than the actual specimen MG=length of drawing/length specimen
How to Draw
Several drawings of one organism may be necessary to represent all features observed, e.g. Anterior view of grasshopper shows all mouth parts properly, but not all limbs. Lateral (side) view shows all the legs. Collection, Observation and Recording of Organisms
Collection
Plants and animals collected from the environment, near school or within school compound using nets, bottles and gloves. Animals collected include:-arthropods, earthworms and small vertebrates like lizards/chameleons/ rodents.


Lateral (side) view shows all the legs. Collection, Observation and Recording of Organisms
Collection
Plants and animals collected from the environment, near school or within school compound using nets, bottles and gloves. Animals collected include:-arthropods, earthworms and small vertebrates like lizards/chameleons/ rodents. Place in polythene bags and take to the laboratory. Stinging/poisonous insects killed using ether. Other animals are observed live and returned to their natural habitat. Plant specimen collected include:- leaves, flowers and whole plants. Observations are made to show the following:-
Plants have roots, stems, leaves and flowers. Animals have legs, hair, hard outer covering, feathers, eyes, mouth, limbs and other appendages,
The differences between animals and plants collected. Comparison Between Plants And Animals
Classification I
Introduction
Classification is putting organisms into groups. Classification is based on the study of external characteristics of organisms. It involves detailed observation of structure and functions of organisms. Organisms with similar characteristics are put in one group. Differences in structure are used to distinguish one group from another. The magnifying lens is an instrument that assists in the observation of fine structure e.g. hairs by enlarging them. Using a Magnifying Lens
A specimen is placed on the bench or held by hand,
Then the magnifying lens is moved towards the eye until the object is dearly focused and an enlarged image is seen. The magnification can be worked out as follows:
length of the drawing
Magnification = length of the specimen
Note: magnification has no units. Nececity/need for Classification
To be able to identify organisms into their taxonomic groups. To enable easier and systematic study of organisms. To show evolutionary relationships in organisms. Major Units of Classification (Taxonomic Groups)
Taxonomy is the study of the characteristics of organisms for the purpose of classifying them. The groups are Taxa (singular Taxon). The taxonomic groups include:
Species: This is the smallest unit of classification. Organisms of the same species resemble each other. The number of chromosomes in their cells is the same. Members of a species interbreed to produce fertile offspring. Genus (plural genera): A genus is made up of a number of species that share several characteristics. Members of a genus cannot interbreed and if they do, the offspring are infertile. Family: A family is made up of a number of genera that share several characteristics.


Genus (plural genera): A genus is made up of a number of species that share several characteristics. Members of a genus cannot interbreed and if they do, the offspring are infertile. Family: A family is made up of a number of genera that share several characteristics. Order: A number of families with common characteristics make an order. Class: Orders that share a number of characteristics make up a class. Phylum/Division: A number of classes with similar characteristics make up a phylum (plural phyla) in animals. In plants this is called a division. Kingdom: This is made up of several phyla (in animals) or divisions (in plants). It is the largest taxonomic unit in classification. Kingdoms
Living organisms are classified into five kingdoms;
Monera,
Protoctista,
Fungi,
Plantae
Animalia. Kingdom Fungi
Some are unicellular while others are multicellular. They have no chlorophyll. Most are saprophytic e.g. yeasts, moulds and mushrooms. A few are parasitic e.g. Puccinia graminae. Kingdom Monera (Prokaryota)
These are very small unicellular organisms. They lack a nuclear membrane
do not have any bound membrane organelles. Hence the name Prokaryota. They are mainly bacteria, e.g. Vibrio cholerae. Kingdom Protoctista
They are unicellular organisms. Their nucleus and organelles are surrounded by membranes (eukaryotic). They include algae, slime moulds - fungi-like and protozoa
Kingdom Plantae
They are all multicellular. They contain chlorophyll and are all autotrophic. They include; Bryophyta (mossplant), Pteridophyta (ferns) and Spermatophyta (seed bearing plants). Kingdom Animalia
These are all multicellular and heterotrophic. Examples are annelida (earthworms), mollusca (snails),athropoda, chordata . Example of Arthropods are ticks, butterflies. Members of Chordata are fish, frogs and humans. External Features of Organisms
In plants we should look for:-
Spore capsule and rhizoids in moss plants. Sori and fronds in ferns. Stem, leaves, roots, flowers, fruits and seeds in plants.


External Features of Organisms
In plants we should look for:-
Spore capsule and rhizoids in moss plants. Sori and fronds in ferns. Stem, leaves, roots, flowers, fruits and seeds in plants. In animals, some important features to look for are:
Segmentation, presence of limbs and, number of body parts, presence and number of antennae. These are found in phylum arthropoda:
Visceral clefts, notochord, nerve tube, fur or hair, scales, fins, mammary glands, feathers and wings. These are found in chordata. Binomial Nomenclature
Organisms are known by their local names. Scientists use scientific names to be able to communicate easily among themselves. This method of naming uses two names, and is called Binomial nomenclature. The first name is the name of the genus: (generic name) which starts with a capital letter. The second name is the name of the species (specific name) which starts with a small letter. The two names are underlined or written in italics. Man belongs to the genus Homo, and the species, sapiens. The scientific name of man is therefore Homo sapiens. Maize belongs to the genus Zea, and the species mays. The scientific name of maize is Zea mays. Practical Activities
Use of Collecting Nets, Cutting Instruments and Hand Lens. Forceps are used to collect crawling and slow moving animals. Sweep nets are used to catch flying insects. Cutting instrument like scapel is used to cut specimen e.g. making sections. Hand lens is used to magnify small plants and animals. Drawing of the magnified organism are made and the linear magnification of each calculated. Collection and Detailed Observation of Small Plants and Animals
e.g. moss, ferns, bean. Look for the following:
Moss plants: Rhizoids and spore capsules. Fern plants: Rhizomes with adventitious roots; large leaves (fronds) with Sori (clusters of sporangia). Seed plants: Tree/shrub (woody) or non-woody (herbs) e.g. bean. Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled.


Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled. Flower - colour, number of parts, size and relative position of each:
Fruits - freshy or dry; edible or not edible. Seeds - monocotyledonous or dicotyledonous. Small animals e.g. earthworms, tick, grasshopper, butterfly, beetles. Observe these animals to see:
Number of legs. Presence or absence of wings. Number of antennae. Body covering. Body parts. THE CELL
Introduction
The cell is the basic unit of an organism. All living organisms are made up of cells. Some organisms are made up of one cell and others are said to be multicellular. Other organisms are made of many cells and are said to be multicellular. Cells are too little to see with the naked eye. They can only be seen with the aid of a microscope. The microscope
The microscope is used to magnify objects. Magnification
The magnifying power is usually inscribed on the lens. To find out how many times a specimen is magnified, the magnifying power of the objective lens is multiplied by that of the eye piece lens. If the eye piece magnification lens is x10 and the objective lens is x4, the total magnification is x40. Magnification has no units. It should always have the multiplication sign.e.g.x40
Microscope parts and their functions
To View the Object
Turn the low power objective lens until it clicks into position. Looking through the eye piece, ensure that enough light is passing through by adjusting the mirror. This is indicated by a bright circular area known as the field of view. Place the slide containing the specimen on stage and clip it into position. Make sure that the specimen is in the centre of the field of view. Using the coarse adjustment knob, bring the low power objective lens to the lowest point. Turn the knob gently until the specimen comes into focus. If finer details are required, use the fine adjustment knob. When using high power objective always move the fine adjustment knob upwards. Care of a Microscope
Great care should be taken when handling it. Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper.


Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper. Make sure that the low power objective clicks in position in line with eye piece lens before and after use. Store the microscope in a dust-proof place free of moisture. Cell Structure as Seen Through the Light Microscope
The cell as seen above has the following:
Cell membrane (Plasma membrane):
This is a thin membrane enclosing cell contents. It controls the movement of substances into and out of the cell. Cytoplasm:
This is a jelly-like substance in which chemical processes are carried out. Scattered all over the cytoplasm are small structures called organelles. Like an animal cell, the plant cell has a cell membrane, cytoplasm and a nucleus. vacuole. Plant cells have permanent, central vacuole. It contains cell sap where sugars and salts are stored. Cell wall:
This is the outermost boundary of a plant cell. It is made of cellulose. Between the cells is a middle lamella made of calcium pectate. Chloroplasts;
With special staining techniques it is possible to observe chloroplasts. These are structures which contain chlorophyll, the green pigment responsible for trapping light for photosynthesis. The Electron Microscope (EM)
Capable of magnifying up to 500,000 times. The specimen is mounted in vacuum chamber through which an electron beam is directed. The image is projected on to a photographic plate. The major disadvantage of the electron microscope is that it cannot be used to observe living objects. However, it provides a higher magnification and resolution (ability to see close points as separate) than the light microscope so that specimen can be observed in more detail. Cell Structure as Seen Through Electron Microscope
The Plasma Membrane
Under the electron microscope, the plasma membrane is seen as a double layer. This consists of a lipid layer sandwiched between two protein layers. This arrangement is known as the unit membrane and the shows two lipid layers with proteins within. Substances are transported across the membrane by active transport and diffusion. The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum.


The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum. An ER that lacks ribosomes is referred to as smooth endoplasmic reticulum. The rough endoplasmic reticulum transports proteins while the smooth endoplasmic reticulum transports lipids. The Ribosomes
These are small spherical structures attached to the ER. They consist of protein and ribonucleic acid (RNA). They act as sites for the synthesis of proteins. Goigi Bodies
Golgi bodies are thin, plate-like sacs arranged in stacks and distributed randomly in the cytoplasm. Their function is packaging and transportation of glycol-proteins. They also produce lysosomes. Mitochondria
Each mitochondrion is a rod-shaped organelle. Made up of a smooth outer membrane and a folded inner membrane. The foldings of the inner membrane are called cristae. They increase the surface area for respiration. The inner compartments called the matrix. Mitochondria are the sites of cellular respiration, where energy is produced. Lysosomes
These are vesicles containing hydrolytic enzymes. They are involved in the breakdown of micro-organisms, foreign macromolecules and damaged or worn-out cells and organelles .. The Nucleus
The nucle s is surrounded by a nuclear membrane which is a unit membrane. The nuclear membrane has pores through which materials can move to the surrounding cytoplasm. The nucleus contains proteins and nucleic acid deoxyribonucleic acid (DNA) and RNA. The chromosomes are found in the nucleus. They are the carriers of the genetic information of the cell. The nucleolus is also located in the nucleus but it is only visible during the non-dividing phase of the cell. The Chloroplasts
These are found only in photosynthetic cells. Each chloroplast consists of an outer unit. membrane enclosing a series of interconnected membranes called lamellae. At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis.


At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis. The light reaction takes place in the lamellae while the dark reactions take place in the stroma. Comparison between animal cell and plant cell
Cell Specialisation
Cells are specialised to perform different functions in both plants and animals. Example;
Palisade cells have many chloroplasts for photosynthesis. Root hair cells are long and thin to absorb water from the soil. Red blood cells have haemoglobin which transports oxygen. Sperm cells have a tail to swim to the egg. Multicellular organisms cells that perform the same function are grouped together to form a tissue. Each tissue is therefore made up of cells that are specialised to carry out a particular function. Animal Tissues- Examples of animal tissues
Plant Tissues
Example of plant tissues
Organs
An organ is made up of different tissues
e.g. the heart, lungs, kidneys and the brain in animals and roots, stems and leaves in plants. Organ systems
Organs which work together form an organ system. Digestive, excretory, nervous and circulatory in animals and transport and support system in plants. organism
Different organ systems form an organism. Practical Activities
Observation and Identification of parts of a light microscope and their functions
A light microscope is provided. Various parts are identified and observed. Drawing and labelling of the microscope is done. Functions of the parts of the mircroscope are stated. Calculations of total magnification done using the formula. Eye piece lens maginification x objective lens rnaginification. Preparation and Observation of Temporary Slides of Plant Cells
A piece of epidermis is made from the fleshy leaf of an onion bulb. It is placed on a microscope slide and a drop of water added. A drop of iodine is added and a cover slip placed on top. Observations are made, under low and medium power objective. The cell wall and nucleus stain darker than other parts. A labelled drawing is made. The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives.


The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives. Labelled drawings of the cells are made. A comparison between plant and animal cell is made. Observation and Estimation of Cell Size and Calculation of Magnification of Plant Cells. Using the low power objective, a transparent ruler is placed on the stage of the microscope. An estimation of the diameter of the field of view is made in millimeters. This is converted into micrometres (1mm=1000u)
A prepared slide of onion epidermal cells is mounted. The cells across the centre of the field of view are counted from left and right and top to bottom. The diameter of field of view is divided by the number of cells lying lengthwise to give an estimate of the length and width of each cell. Cell Physiology
Meaning of cell physiology
The term physiology refers to the functions that occur in living organisms. Cell physiology refers to the process through which substances move across the cell membrane. Several physiological processes take place inside the cell.e.g. respiration. Oxygen and glucose required enter the cell while carbon (IV) oxide and water produced leave the cell through the cell membrane. Structure and properties of cell membrane
The cell membrane is the protective barrier that shelter cellular contents. Movement of all substances into and out of the cells takes place across the cell membrane. It is made up of protein and lipid molecules. Lipid molecules have phosphate group attached to it on one end. They are then referred to phospholipids. The phospholipids are arranged to form a double layer. The ends with phosphate group face outwards. the proteins are scattered throughout the lipid double layer. Some of these proteins act as carrier molecules that channel some material in and outside the cells. The cell membrane allows certain molecules to pass through freely while others move through with difficulty and still others do not pass through at all. This is selective permeability and the cell membrane is described as semi-permeable. Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer.


Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer. Polarlity
The cell membrane has electrical charges across its surface.it has positive charged ions on the outside and negatively charged ions on the inside.this property contributes to electrical impulses sent along nerve cells. Sensitivity to changes in temperature and pH
Very high temperatures destroy the semi-permeability nature of the cell membrane because the proteins are denatured by extreme pH values have the same effect on the membrane permeability. Physiological processes
Some of the physiological processes include diffusion, osmosis and active transport. Diffusion
Diffusion is the movement of molecules or ions from a region of high concentration to a region of low concentration aided by a concentration gradient.. diffusion continues to occur as long as there is a difference in concentration between two regions (concentration gradient). Stops when an equilibrium is reached i.e., when the concentration of molecules is the same in both regions. Diffusion is a process that occurs inside living organisms as well as the external environment.. Does not require energy. Factors Affecting Diffusion
.~ -
Concentration Gradient
An increase in the concentration of molecules at one region results in a steeper concentration gradient which in turn increases the rate of diffusion. Temperature
High temperature increases kinetic energy of molecules. They move faster hence resulting in an increase in rate of diffusion, and vice versa. Size of Molecules or Ions
The smaller the size of molecules or ions, the faster their movement hence higher rate of diffusion. Density
The denser the molecules or ions diffusing, the slower the rate of diffusion, and vice versa. Medium
The medium through which diffusion occurs also affects diffusion of molecules or ions. For example, diffusion of molecules through gas and liquid media is faster than through a solid medium. Distance
This refers to the thickness or thinness of surface across which diffusion occurs. Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms.


Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms. Role of Diffusion in Living Organisms
Some processes that depend on diffusion include the following:
Gaseous exchange: Movement of gases through respiratory surfaces is by diffusion. Absorption of materials into cells Cells obtain raw materials and nutrients from the surrounding tissue fluid and blood through diffusion, e.g., glucose needed for respiration diffuses from blood and tissue fluid into cells. Excretion: Removal of metabolic waste products like carbon (IV) oxide, and ammonia out of cells is by diffusion. Absorption of the end-products of digestion from the intestines is by diffusion. Osmosis
Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane. Osmosis is a special type of diffusion that involves the movement of water molecules only and not solute molecules. Osmosis takes place in cells across the cell membrane as well as across non-living membranes
e.g. cellophane or visking tubing which are also semi-permeable,
It is purely a physical process. Factors Affecting Osmosis
Size of solute molecules-
Osmosis' occurs only when solute molecules are too large to pass through a semi-permeable membrane. Concentration Gradient . Osmosis occurs when two solutions of unequal solute concentration are separated by a semi-permeable membrane. Temperature ,. High temperatures increase movement of water molecules hence influence osmosis. However, too high temperatures denature proteins in cell membrane and osmosis stops. Pressure
Increase in pressure affects movement of water molecules. As pressure increases inside a plant cell, osmosis decreases. Roles of Osmosis in Living Organisms
The following processes depend on osmosis in living organisms:
Movement of water into cells from the surrounding tissue fluid and also from cell to cell. Absorption of water from the soil and into the roots of plants. Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules.


Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules. Opening and closing stomata. Water Relations in Plant and Animal Cells
The medium (solution) surrounding cells or organisms is described by the terms hypotonic, hypertonic and isotonic. A solution whose solute concentration is more than that of the cell sap is said to be hypertonic. A cell placed in such a solution loses water to the surroundings by osmosis. A solution whose solute concentration is less than that of the cell sap is said to be hypotonic. A cell placed in such a solution gains water from the surroundings by osmosis. A solution which has the same solute concentration as the cell sap is said to be isotonic. When a cell is placed in such a solution there will be no net movement of water either into or out of the cell. Osmotic Pressure
The term osmotic pressure describes the tendency of the solution with a high solute concentration to draw water into itself when it is separated from distilled water or dilute solution by a semi-permeable membrane. Osmotic pressure is measured by an osmometer. When plant cells are placed in distilled water or in a hypotonic solution, the osmotic pressure in the cells is higher than the osmotic pressure of the medium. This causes the water to enter the cells by osmosis. The water collects in the vacuole which increases in size. As a result the cytoplasm is pushed outwards and it in turn presses the cell membrane next to the cell wall. This builds up water pressure (hydrostatic pressure) inside the cell. When the cell is stretched to the maximum, the cell wall prevents further entry of water into the cell. Then the cell is said to be fully turgid. The hydrostatic pressure developed is known as turgor pressure. Plasmolysis
When a plant cell is placed in a hypertonic medium, it loses water by osmosis. The osmotic pressure of the cell is lower than that of the medium. The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis.


The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis. Incipient plasmolysis is when a cell membrane just begins to lose contact with the cell wall. Plasmolysis can be reversed by placing the cell in distilled water or hypotonic solution. However, full plasmolysis may not be reversed if cell stays in that state for long. Wilting
The term wilting describes the drooping of leaves and stems of herbaceous plants after considerable amounts of water have been lost through transpiration. It is observed in hot dry afternoons or in dry weather. This is when the amount of water lost through transpiration exceeds the amount absorbed through the roots. Individual cells lose turgor and become plasmolysed and the leaves and stems droop. The condition is corrected at night when absorption of water by the roots continue while transpiration is absent. Eventually, wilting plants may die if the soil water is not increased through rainfall or watering. Water Relations in Plants and Animals
Haemolysis
Haemolysis is the bursting of cell membrane of red blood cells releasing their haemoglobin. It occurs when red blood cells are placed in distilled water or hypotonic solution. This is because the cell membrane does not resist further entry of water by osmosis after maximum water intake. Crenation
Takes place when red blood cells are placed in hypertonic solution. They lose water by osmosis, shrink and their shape gets distorted. Animal cells have mechanisms that regulate their salt water balance (osmoregulation) to prevent above processes that lead to death of cells. An Amoeba placed in distilled water, i.e. hypotonic solution, removes excess water using a contractile vacuole. The rate of formation of contractile vacuoles increases. Active Transport
Active transport is the movement of solutes such as .glucose, amino acids and mineral ions;
From an area of their low concentration to an area of high concentration. It is movement against a concentration gradient and therefore energy is required. As such it only takes place in living organisms. The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it.


The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it. It has been shown that the substance fits into a particular slot on the protein molecule,
As the protein changes from one form of shape to another the substance is moved across and energy is expended. Factors Affecting Active Transport
Availability of oxygen
Energy needed for active transport is provided through respiration. An increase in the amount of oxygen results in a higher rate of respiration. If a cell is deprived of oxygen active transport stops . Temperature
Optimum temperature is required for respiration, hence for active transport. Very high temperatures denature respiratory enzymes. Very low temperatures inactivate enzymes too and active transport stops. Availability of carbohydrates
Carbohydrates are the main substrates for respiration. Increase in amount of carbohydrate results in more energy production during respiration and hence more active transport. Lack of carbohydrates causes active transport to stop. Metabolic poisons
Metabolic poisons e.g. cyanide inhibit respiration and stops active transport due to lack of energy. Role of Active Transport in Living Organisms
Processes requiring active transport:
Absorption of mineral salts from the soil into plant roots. Absorption of end products of digestion e.g. glucose and amino acids from the digestive tract into blood stream. Excretion of metabolic products e.g.urea from the cells. Re-absorption of useful substances and mineral salts back into blood capillaries from the kidney tubules. Sodium-pump mechanism in nerve cells. Re-absorption of useful materials from tissue fluid into the blood stream. Practical Activities
1.Experiment to Demonstrate Diffusion
Various coloured substances such as: dyes, plant extracts and chemicals like potassium pennanganate are used. Potassium manganate (VII) crystals are introduced to the bottom of a beaker filled with water using a glass tubing or drinking straw which is then removed. Observations are made and the disappearance of the crystals and subsequent uniform colouring of water noted. 2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry.


2.Experiment to Demonstrate Osmosis Using a Visking Thbing
A strip of visking tubing 8-10 cm is cut and tied at one end using strong thread. About 2 ml of 25% sucrose solution is put inside and the other end tied with thread. The tubing is washed under running water and then blotted to dry. It is immersed in a beaker containing distilled water and left for at least one hour or overnight. It will then be observed that the visking tubing has greatly increased in size and has become firm. A control experiment can be set up using distilled water inside the visking tubing in place of sucrose solution. 3.Experiment to Show Osmosis using Living Tissue
Irish potato tubers are peeled and scooped out to make hollow space at the centre. Sucrose solution is placed inside the hollow, and the potato tuber placed in a beaker or petri-dish with distilled water. A conttrol is set using a boiled potato. Another one using distilled water inside hollow in place of sugar solution. The experiment is left for 3 hours to 24 hours. 4.Experiment to Demonstrate Turgor and Plasmolysis in Onion Epidermal Cells
Two strips of onion epidermis are obtained. One is placed on a slide with distilled water while the other is placed on a slide with 25% sucrose solution and a coverslip placed on top of each. The mounted epidermis is observed under low power microscope and then left for 30 minutes. After 30 minutes, observations are made again. The cells in distilled water have greatly enlarged. Cells in 25% sucrose have shrunk. Nutrition in Plants and Animals
Structure of the Leaf
External Structure
The external structure of the leaf consists of a leaf stalk or petiole and a broad leaf blade or lamina. The lamina has a main vein midrib from which smaller veins originate. The outline of the leaf is the margin and the tip forms the apex. Internal Structure of the Leaf
Epidermis
This is the outer layer of cells, normally one cell thick. It is found in both the upper and lower leaf surfaces. The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation.


The cells are arranged end to end. The epidermis offers protection and maintains the shape of the leaf. It is covered by a layer of cuticle which reduces evaporation. Leaf Mesophyll
Consists of the palisade layer, next to upper epidermis, and the spongy layer next to the lower epidermis. Palisade Mesophyll Layer
The cells are elongated and arranged close to each other leaving narrow air spaces. These contain numerous chloroplasts and are the main photosynthetic cells. In most plants, the chloroplast are distributed fairly uniformly throughout the cytoplasm. In certain plants growing in shaded habitats in dim light, most chloroplasts migrate to the upper region of the palisade cells in order to maximise absorption of the limited light available. Spongy Mesophyll Layer
The cells are spherical in shape. They are loosely arranged, with large intercellular spaces between them. The spaces are airfilled and are linked to the stomatal pores. The spongy mesophyll cells have fewer chloroplasts than the palisade mesophyll cells. Vascular Bundles
These are made up of the xylem and the phloem tissues. The xylem transports water and mineral salts to the leaves. The phloem transports food manufactured in the leaf to the other parts of the plant and from storage organs to other parts. Adaptations of Leaf for Photosynthesis
Presence of veins with vascular bundles. Xylem vessels transport water for photosynthesis. Phloem transports manufactured food from leaves to other parts of the plant. Leaf lamina is thin to allow for penetration of light over short distance to reach photosynthetic cells. Broad lamina provides a large surface area for absorption of light and carbon (IV) oxide. Transparent cuticle and epidermal layer allow light to penetrate to mesophyll cells. Palisade cells are close to the upper epidermis for maximum light absorption. Presence of numerous chloroplasts in palisade mesophyll traps maximum light. Chloroplast contain chlorophyll that traps light energy. Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light.


Spongy mesophyll layer has large intercellular air spaces allowing for gaseous exchange. Presence of stomata for efficient gaseous exchange (entry of carbon (IV) oxide into leaf and exit of oxygen). Mosaic arrangement of leaves to ensure no overlapping of leaves hence every leaf is exposed to light. Structure and Function of Chloroplasts
Chloroplasts are large organelles (5 um in diameter) found in the cytoplasm of green plant cells. They are visible under the light microscope. They contain chlorophyll, a green pigment and other carotenoids which are yellow, orange and red in colour. Certain plants have red or purple leaves due to abundance of these other pigments. Chlorophyll absorbs light energy and transforms it into chemical energy. The other pigments absorb light but only to pass it onto chlorophyll. The wall of chloroplast consists of an outer and an inner membrane. The two make up the chloroplast envelop. Inner membrane encloses a system of membranes called lamellae. At intervals, the membranes form stacks of fluid filed sacs known as grana (singular granum). Chloroplast and other pigments are attached to the grana. In between the lamellae is a gel-like stroma, that contains starch grains and lipid droplets. Enzymes for the dark stage reaction (light independent stage) are embedded in the stroma. Enzymes for the light dependent stage occur in the grana. Functions
• .Absorption of light by chlorophyll and other pigments. Light stage of photosynthesis occurs on the grana. (transformation of light energy to chemical energy.)
Carbon fixation to form carbohydrate takes place in the stroma which has enzymes for dark stage of photosynthesis. Process of Photosynthesis
Photosynthesis involves a series of chemical reactions, all of which take place inside chloroplasts. A general equation for photosynthesis is:
Carbon (IV)Oxide+Water light energy---Glucose+Oxygen
chlorophyll
6CO2+6H2O light C6H12O+6O2
chlorophyll
The reaction occurs in two main phases or stages. The initial state requires light and it is called the light dependent stage or simply light stage. It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage.


It takes place on the lamellae surfaces. Its products are used in the dark stage. The dark stage does not require light although it occurs in the light and is called light independent stage. Light-Stage
Two reactions take place that produce raw materials for the dark stage:
Light energy splits the water molecules into hydrogen and oxygen. This process is called photolysis. The hydrogen is taken up by a hydrogen acceptor called Nicotinamide adenine dinucleotide phosphate (NADP) while oxygen is released as a by-product. 2H2O(l) light energy4H+O2
photolysis
Light energy strikes the chlorophyll molecules and sets in motion a series of reactions resulting in the production of a high energy molecule called adenosine triphophate (ATP). Dark Stage
This stage involves the fixation of carbon i.e. the reduction of carbon (IV) oxide by addition of hydrogen to form carbohydrate. It uses the products formed during the light stage. ATP
Carbon + Hydrogen --- Carbohydrates
(IV) oxide
The synthesis of carbohydrates does not take place in a simple straight line reaction as shown in the equation above. It involves a series of steps that constitute what is known as the Calvin cycle. Carbon (IV) oxide is taken up by a compound described as a carbon (IV) oxide acceptor. This is a 5-carbon compound known as ribulose biphosphate and a six carbon compound is formed which is unstable and splits into two three-carbon compounds. Hydrogen from the light reaction is added to the three carbon compound using energy (ATP) from the light reaction. The result is a three carbon (triose) sugar, (phosphoglycerate or PGA). This is the first product of photosynthesis. Glucose, other sugars as well as starch are made from condensation of the triose sugar molecules. The first product is a 3-carbon sugar which condenses to form glucose (6-C sugar). From glucose, sucrose and eventually starch is made. Sucrose is the form in which carbohydrate is transported from the leaves to other parts of the plant. Starch is the storage product. Other substances like oils and proteins are made from sugars. This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place.


This involves incorporation of other elements e.g. nitrogen, phosphorus and sulphur. Factors Influencing Photosynthesis
Certain factors must be provided for before photosynthesis can take place. The rate or amount of photosynthesis is also influenced by the quantity or quality of these same factors. Carbon(IV) Oxide Concentration
Carbon (IV) oxide is one of the raw materials for photosynthesis. No starch is formed when leaves are enclosed in an atmosphere without carbon (IV) oxide. The concentration of carbon (IV) oxide in the atmosphere remains fairly constant at about 0.03% by volume. However, it is possible to vary the carbon (IV) oxide concentration under experimental conditions. Increasing the carbon (IV) oxide concentration up to 0.1 % increases the rate of photosynthesis. Further increase reduces the rate. Light Intensity
Light supplies the energy for photosynthesis. Plants kept in the dark do not form starch. Generally, increase in light intensity up to a certain optimum, increases the rate of photosynthesis. The optimum depends on the habitat of the plant. Plants that grow in shady places have a lower optimum than those that grow in sunny places. Water
Water is necessary as a raw material for photosynthesis. The amount of water available greatly affects the rate of photosynthesis. The more water available, the more the photosynthetic rate, hence amount of food made. Effect of water on photosynthesis can only be inferred from the yield of crops. It is the main determinant of yield (limiting factor in the tropics). Temperature
The reactions involved in photosynthesis are catalysed by a series of enzymes. A suitable temperature is therefore necessary. The optimum temperature for photosynthesis in most plants is around 30"C. This depends on the natural habitat of the plant. Some plants in temperate regions have 20°C as their optimum while others in the tropics have 45°C as their optimum temperature. The rate of photosynthesis decreases with a decrease in temperature below the optimum. In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g.


In most plants, photosynthesis stops when temperatures approach O°C although some arctic plant species can photosynthesise at -2°C or even -3°C. Likewise, increase in temperature above the optimum decreases the rate and finally the reactions stop at temperatures above 40°c due to enzyme denaturation. However, certain algae that live in hot springs e.g. Oscilatoria can photosynthesise at 75°C
Chlorophyll
Chlorophyll traps or harnesses the energy from light. Leaves without chlorophyll do not form starch. Chemical Compounds Which Constitute Living Organisms
All matter is made up of chemical elements, each of which exists in the form of smaller units called atoms. Some of the elements occur in large amounts in living things. These include carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus. Elements combine together to form compounds. Some of these compounds are organic. Organic compounds contain atoms of carbon combined with hydrogen and they are usually complex. Other compounds are inorganic. Most inorganic compounds do not contain carbon and hydrogen and they are usually less complex. Cells contain hundreds of different classes of organic compounds. However, there are four classes of organic compounds found in all cells. These are: carbohydrates, lipids, proteins and nucleic acids. Carbohydrates
Carbohydrates are compounds of carbon, hydrogen and oxygen. Hydrogen and oxygen occur in the ratio of 2: 1 as in water. Carbohydrates are classified into three main groups: monosaccharides, disaccharides and polysaccharides. Monosaccharides
These are simple sugars. The carbon atoms in these sugars form a chain to which hydrogen and oxygen atoms are attached. Monosaccharides are classified according to the number of carbon atoms they possess. The most common monosaccharides are:
Glucose - found free in fruits and vegetables. Fructose - found free in fruits and in bee honey. Galactose - found combined in milk sugar. The general formula for these monosaccharides is (CH2O)n where n is 6. They have the same number of carbon, hydrogen and oxygen molecules i.e. C6H12O6. Properties of Monosaccharides
They are soluble in water. They are crystallisable. They are sweet. The are all reducing sugars.


They are crystallisable. They are sweet. The are all reducing sugars. This is because they reduce blue copper (II) sulphate solution when heated to copper oxide which is red in colour and insoluble. Functions of Monosaccharides
They are oxidised in the cells to produce energy during respiration. Formation of important biological molecules e.g. deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Some monosaccharides are important metabolic intermediates e.g. in photosynthesis and in respiration. Monosaccharides are the units from which other more complex sugars are formed through condensation. Disaccharides
These contain two monosaccharide units. The chemical process through which a large molecule (e.g. a disaccharide) is formed from smaller molecules is called condensation and it involves loss of water. Common examples of disaccharides include sucrose, maltose and lactose. Disaccharides are broken into their monosaccharide units by heating with dilute hydrochloric acid. This is known as hydrolysis and involves addition of water molecules. The same process takes place inside cells through enzymes. Sucrose+water_--hydrolysis-----------------glucose+fructose
Properties of Disaccharides
Sweet tasting. Soluble in water. Crystallisable. Maltose and lactose are reducing sugars while sucrose is non-reducing sugar. Sucrose is the form in which carbohydrate is transported in plants:
This is because it is soluble andjchernically stable. Sucrose is a storage carbohydrate in some plants e.g. sugar-cane and sugar-beet. Disaccharides are hydrolysed to produce monosaccharide units which are readily metabolised by cell to provide energy. Polysaccharides
If many monosaccharides are joined together through condensation, a polysaccharide is formed. Polysaccharides may consist of hundreds or even thousands of monosaccharide units. Examples of polysaccharides:
Starch - storage material in plants. Glycogen is a storage carbohydrate in animals like starch, but has longer chains. Inulin - a storage carbohydrate in some plants e.g. Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods.


Dahlia. Cellulose - structural carbohydrate in plants. Chitin - forms exoskeleton in arthropods. Importance and Functions of Polysaccharides
They are storage carbohydrates - starch in plants glycogen in animals. They are hydrolysed to their contituent monosaccharide units and used for respiration. . They form structural material e.g. cellulose makes cell walls. Cellulose has wide commercial uses e.g. Fibre in cloth industry. Cellulose is used to make paper. Carbohydrates combine with other molecules to form important structural compounds in living organisms. Examples are:
Pectins: Combine with calcium ions to form calcium pectate. Chitin: Combine with (NH) group. Makes the exoskeleton of arthropods, and walls of fungi. Lipids
These are fats and oils. Fats are solid at room temperature while oils are liquid. They are made up of carbon, oxygen and hydrogen atoms. The structural units of lipids are fatty acids and glycerol. Fatty acids are made up of hydrocarbon chain molecules with a carboxyl group (-COOH) at one end. In the synthesis of a lipid, three fatty acid molecules combine with one glycerol molecule to form a triglyceride. Three molecules of water are lost in the process. This is a condensation reaction and water is given off. Lipids are hydrolysed e.g. during digestion to fatty acids and glycerol, water is added. condensation
-
Glycerol + 3 Fatty hydrolysis Lipid + Water acids
Properties
Fats are insoluble in water but dissolve in organic solvents e.g. in alcohols. They are chemically inactive, hence used as food storage compounds. Functions of Lipids
Structural materials - as structural material they make up the cell membrane. Source of energy - they are energy rich molecules. One molecule of lipid provides more energy than a carbohydrate molecule. Storage compound - They are stored as food reserves in plants. In animals e.g. mammals, all excess food taken is converted to fats which are stored in adipose tissue, and around internal organs such as the heart and kidneys. Insulation - They provide insulation in animals living in cold climates. A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g.


A lot of fat is stored under the skin e.g. blubber in seals. Protection - Complex lipids e.g. wax on leaf surfaces protects the plant against water-loss and overheating. Fats stored around some internal organs acts as shock absorbers, thus protecting the organs. Source of Metabolic Water -:-lipids when oxidised produce metabolic water which supplements water requirements in the body. Desert animals e.g. the camel accumulate large quantities of fat in the hump which when oxidised releases metabolic water. Proteins
Proteins are the most abundant organic compounds in cells and constitute 50% of total dry weight. Proteins are compounds which are made up of carbon, hydrogen, nitrogen, oxygen and sometimes sulphur and phosphorus. The structural units of proteins are amino acids. The nature of a protein is determined by the types of amino acids it is made of. There are about 20 common amino acids that make up proteins. Essential and Non-Essential Amino Acids
Essential amino acids are those which cannot be synthesised in the body of an organism and must therefore be provided in the diet. There are ten amino acids which are essential for humans. These are valine, leucine, phenylalanine, lysine, tryptophan, isoleucine, methionine, threonine, histidine and arginine. Non-essential amino acids are those which the body can synthesise and therefore need not be available in the diet. There are ten of them. These are glycine, alanine, glutamic acid, aspartic acid, serine, tyrosine, proline, glutamine, arginine and cysteine. Proteins are essential in the diet because they are not stored in the body. Excess amino acids are deaminated. Formation of Proteins
Proteins are made up of many amino acid units joined together through peptide bonds. When two amino acids are joined together a dipeptide is formed. The chemical process involved is called condensation and a molecule of water is eliminated . When many amino acids are joined together a polypeptide chain is formed. The nature of a particular protein depends on the types, number and sequence of amino acids from which it is made. Functions of Proteins
As structural materials proteins-
Are the basic building structures of protoplasms. Proteins in conjunction with lipid form the cell membrane.