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ray of enzyme cofactors and metabolic intermediates. And, last but certainly not least, they are the constituents of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), the molecular repositories of genetic information. The structure of every protein, and ultimately of every biomolecule and cellular ...
when the substituted atom is exocyclic (not within the ring structure), in which case the type of atom is identified and the ring position to which it is attached is denoted with a superscript. The amino nitrogen attached to C-6 of adenine is N6; similarly, the carbonyl oxygen and amino nitrogen at C-6 and C-2 of guan...
line of how genetic information is processed by the cell is now a prerequisite for the discussion of any area of biochemistry. Here, we concern ourselves with DNA structure itself, the events 280 Chapter 8 Nucleotides and Nucleic Acids that led to its discovery, and more recent refinements in our understanding. RNA str...
iodicities observed in the xray diffraction patterns of DNA fibers, Watson and Crick manipulated molecular models to arrive at a structure FIGURE 8–14 X-ray diffraction pattern of DNA. The spots forming a cross in the center denote a helical structure. The heavy bands at the left and right arise from the recurring base...
forms. Palindromic DNA (or RNA) sequences can form alternative structures with intrastrand base pairing. (a) When only a single DNA (or RNA) strand is involved, the structure is called a hairpin. (b) When both strands of a duplex DNA are involved, it is called a cruciform. Blue shading highlights asymmetric sequences t...
structure that serves as a reference point, as does the double helix for DNA. The three-dimensional structures of many RNAs, like those of proteins, are complex and unique. Weak interactions, especially base-stacking interactions, play a major role in stabilizing RNA structures, just as they do in DNA. Where complement...
imen, under fixed conditions of pH and ionic strength, can yield an estimate of its base composition. If denaturation conditions are carefully controlled, regions that are rich in AUT base pairs will specifically denature while most of the DNA remains tm tm 75 80 Temperature (°C) 85 100 ) % ( 50 0 100 ) 80 60 40 20 (a)...
ents (Fig. 8–35) are (1) deaminating agents, particularly nitrous acid (HNO2) or compounds that can be metabolized to nitrous acid or nitrites, and (2) alkylating agents. Nitrous acid, formed from organic precursors such as nitrosamines and from nitrite and nitrate salts, is a potent accelerator of the deamination of b...
very large DNAsequencing projects are in progress. Perhaps the most ambitious of these is the Human Genome Project, in which researchers have sequenced all 3.2 billion base pairs of the DNA in a human cell (Chapter 9). Dideoxy Sequencing of DNA The Chemical Synthesis of DNA Has Been Automated Another technology that h...
oenzyme incorporating adenosine is 5-deoxyadenosylcobalamin, the active form of vitamin B12 (see Box 17-2), which participates in intramolecular group transfers between adjacent carbons. func- O CH2 NH2 Nicotinamide O O P O O CH2 O H H H NH2 N N N N H CH3 CH3 O N H N O N N CH2 CHOH CHOH CHOH CH2 O O OP O O P O O CH2 O ...
label. A sample of the DNA was reacted with DNA polymerase and each of the nucleotide mixtures (in an appropriate buffer) listed below. Dideoxynucleotides (ddNTPs) were added in relatively small amounts. 1. dATP, dTTP, dCTP, dGTP, ddTTP 2. dATP, dTTP, dCTP, dGTP, ddGTP 3. dATP, dCTP, dGTP, ddTTP 4. dATP, dTTP, dCTP, dG...
s of enzymes lie at the heart of the general approach to generating and propagating a recombinant DNA molecule (Fig. 9–1). First, restriction endonucleases (also called restriction enzymes) recognize and cleave DNA at specific DNA sequences (recognition sequences or restriction sites) to generate a set of smaller fragm...
ognition sequences for several restriction endonucleases can be inserted into a plasmid that has been cleaved by a restriction endonuclease. The insert is called a linker; an insert with multiple restriction sites is called a polylinker. or a similar cofactor. The base-pairing of complementary sticky ends greatly facil...
bp (a simple genome by eukaryotic standards, less than four times the size of the E. coli chromosome), and its entire sequence is known. Yeast is also very easy to maintain and grow on a large scale in the laboratory. Plasmid vectors have been constructed for yeast, employing the same principles that govern the use of...
onvenient versions supplied by the vector. Generally, a well-characterized promoter and its regulatory elements are positioned near several unique restriction sites for cloning, so that genes inserted at the restriction sites will be expressed from the regulated promoter element (Fig. 9–11). Some of these vectors incor...
g clones with overlapping sequences. A set of overlapping clones represents a catalog for a long contiguous segment of a genome, often referred to as a contig (Fig. 9–13). Previously studied sequences or entire genes can be located within the library using hybridization methods to determine which library clones harbor ...
ved from a bacterium that lives at 90 C), which remains active after every heating step and does not have to be replenished. Careful design of the primers used for PCR, such as including restriction endonuclease cleavage sites, can facilitate the subsequent cloning of the amplified DNA (Fig. 9–16b). This technology is ...
ence Victim S uspect 2 S Denature DNA, and transfer to nylon membrane. Incubate with probe, then wash. Expose x-ray film to membrane. out the genome at random. The sequenced segments were ordered by the computerized identification of sequence overlaps (with some reference to the public project’s detailed physical map)....
tein product of the gene. There are three other main paths to investigating protein function: (1) sequence and structural comparisons with genes and proteins of known function, (2) determination of when and where a gene is expressed, and (3) investigation of the interactions of the protein with other proteins. We discu...
known function with one whose function is known can provide a useful and compelling “guilt by association.” The techniques used in this effort are quite varied. Comparisons of Genome Composition Although not evidence of direct association, the mere presence of combinations of genes in particular genomes can hint at 888...
en and where its gene is expressed. Researchers use DNA microarrays (chips) and protein chips to explore gene expression at the cellular level. ■ Several new techniques, including comparative genomics, immunoprecipitation, and yeast twohybrid analysis, can identify protein-protein interactions. These interactions provi...
plant cells that grow in this medium generally contain the foreign gene. 8885d_c09_306-342 2/7/04 8:14 AM Page 333 mac76 mac76:385_reb: 9.4 Genome Alterations and New Products of Biotechnology 333 FIGURE 9–29 A tobacco plant expressing the gene for firefly luciferase. Light was produced after the plant was watered with...
sformation (chromosomal integration). When the injected eggs are introduced into a female mouse and allowed to develop, the new gene is often expressed in some of the newborn mice. Those in which the germ line has been FIGURE 9–33 Cloning in mice. The gene for human growth hormone was introduced into the genome of the ...
four patients who had received cells with the correct cytokine receptor gene developed a severe form of leukemia. During the gene therapy treatment, one of the introduced retroviruses had by chance inserted itself into a chromosome of one CD34 cell, resulting in abnormally high expression of a gene called LMO- Glu–Thr...
ing Harbor Laboratory Press, Cold Spring Harbor, NY. Although supplanted by more recent manuals, this threevolume set includes much useful background information on the biological, chemical, and physical principles underlying both classic and still-current techniques. Gene Cloning Arnheim, N. & Erlich, H. (1992) Polyme...
mes in succession. In individuals with adult-onset HD, this codon is typically repeated 40 to 55 times. In individuals with childhood-onset HD, this codon is repeated more than 70 times. The length of this simple trinucleotide repeat indicates whether an individual will develop HD, and at approximately what age the fir...
HDL (good cholesterol), it is generally recommended that one avoid large amounts of these fatty acids. Unfortunately, French fries, doughnuts, and cookies tend to be high in trans fatty acids. The physical properties of the fatty acids, and of compounds that contain them, are largely determined by the length and degree...
g deep dives in cold water (Box 10–1). Many Foods Contain Triacylglycerols Most natural fats, such as those in vegetable oils, dairy products, and animal fat, are complex mixtures of simple and mixed triacylglycerols. These contain a variety of fatty acids differing in chain length and degree of saturation (Fig. 10–4)....
a are variable; that shown here has two very long, branched alkyl chains, each end in ether linkage with a glycerol moiety. In phospholipids the polar head group is joined through a phosphodiester, whereas glycolipids have a direct glycosidic linkage between the head-group sugar and the backbone glycerol. Glycerophosph...
lycerophospholipids. When a fatty acid is attached in amide linkage to the ONH2 on C-2, the resulting compound is a ceramide, which is structurally similar to a diacylglycerol. Ceramide is the structural parent of all sphingolipids. There are three subclasses of sphingolipids, all derivatives of ceramide but differing ...
naling by steroid hormones (Chapter 12), the remarkable biosynthetic pathway to cholesterol, and the transport of cholesterol by lipoprotein carriers (Chapter 21). 10.2 Structural Lipids in Membranes 355 26CH3 25C H 27CH3 24C H2 23C H2 Alkyl side chain 22C H2 H 21CH3 20C 18CH3 17 13 D 14 12 C 16 15 19CH3 11 9 Polar hea...
membrane (see Fig. 12–8). Membrane sphingolipids also can serve as sources of intracellular messengers. Both ceramide and sphingomyelin (Fig. 10–12) are potent regulators of protein kinases, and ceramide or its derivatives are known to be involved in the regulation of cell division, differentiation, migration, and prog...
evels in kidney and bone. Deficiency of vitamin D 10.3 Lipids as Signals, Cofactors, and Pigments 361 leads to defective bone formation and the disease rickets, for which administration of vitamin D produces a dramatic cure. Vitamin D2 (ergocalciferol) is a commercial product formed by UV irradiation of the ergosterol ...
ic enzymes (phospholipases, glycosidases) to yield their component parts for analysis. Some methods commonly used in lipid analysis are shown in Figure 10–23 and discussed below. Lipid Extraction Requires Organic Solvents Neutral lipids (triacylglycerols, waxes, pigments, and so forth) are readily extracted from tissue...
atomic mass units (amu) apart represents loss of each successive methyl and methylene group from the right end of the molecule (C-18 of the fatty acid), until the ion at m/z 300 is reached. This is followed by a gap of 26 amu for the carbons of the terminal double bond, at m/z 274; a further gap of 14 amu for the C-11...
phatidylcholine, cholesteryl palmitate (a sterol ester), sphingomyelin, palmitate, n-tetradecanol, triacylglycerol, and cholesterol. In what order do you expect the lipids to elute from the column? Explain your reasoning. Johann Thu12. Identification of Unknown Lipids dichum, who practiced medicine in London about 100 ...
n. The outer membrane of E. coli, which encloses the plasma membrane, has a different function (protection) and a different set of proteins. Some membrane proteins are covalently linked to complex arrays of carbohydrate. For example, in glycophorin, a glycoprotein of the erythrocyte plasma membrane, 60% of the mass con...
ns and hydrogen bonding with the hydrophilic domains of integral proteins and with the polar head groups of membrane lipids. They can be released by relatively mild treatments that interfere with electrostatic interactions or break hydrogen bonds; a commonly used agent is carbonate at high pH. Peripheral proteins may s...
s are on the surface (recall the structures of myoglobin and hemoglobin, for example). In Chapter 19 we will encounter several complex membrane proteins having multiple transmembrane helical segments in which hydrophobic chains are positioned to interact with the lipid bilayer. The Topology of an Integral Membrane Prot...
a number of outer membrane proteins of gram-negative bacteria (Fig. 11–13) have been correctly predicted, by sequence analysis, to contain barrels. Covalently Attached Lipids Anchor Some Membrane Proteins Some membrane proteins contain one or more covalently linked lipids of several types: long-chain fatty acids, isopr...
droxymyristic acid Ratio of unsaturated to saturated† 4 18 26 38 13 4 25 24 34 10 2.9 2.0 4 29 23 30 10 1.6 40 C 8 48 9 12 8 0.38 Source: Data from Marr, A.G. & Ingraham, J.L. (1962) Effect of temperature on the composition of fatty acids in Escherichia coli. J. Bacteriol. 84, 1260. *The exact fatty acid composition de...
ge reinforce each other and the noise in individual images is averaged out, yielding a highresolution image of the protein (inset in Fig. 2a). AFM of purified E. coli aquaporin, reconstituted into Laser light detector (detects cantilever deflection) + – Laser Cantilever Sample z x y Platform moves to maintain constant ...
brane Fusion Is Central to Many Biological Processes A remarkable feature of the biological membrane is its ability to undergo fusion with another membrane without losing its continuity. Although membranes are stable, they are by no means static. Within the eukaryotic endomembrane system (which includes the nuclear mem...
em to diffuse through the lipid bilayer. With very few exceptions, the traffic of small molecules across the plasma membrane is mediated by proteins such as transmembrane channels, carriers, or pumps. Within the eukaryotic cell, different compartments have different concentrations of metabolic intermediates and product...
s several orders of magnitude greater than those typical of carriers, rates approaching the limit of unhindered diffusion. Channels typically show less stereospecificity than carriers and are usually not saturable. Most channels are oligomeric complexes of several, often identical, subunits, whereas many carriers funct...
he capacity of the blood to carry carbon dioxide from the tis reenters the erysues to the lungs. In the lungs, HCO3 throcyte and is converted to CO2, which is eventually released into the lung space and exhaled. To be effec- tive, this shuttle requires very rapid movement of HCO3 across the erythrocyte membrane. The ch...
trical potential (in volts). Eukaryotic cells typically have electrical potentials across their plasma membranes of about 0.05 to 0.1 V (with the inside negative relative to the outside), so the second term of Equation 11–3 can make a significant contribution to the total free-energy change for transporting an ion. Mos...
residue in another are central to the Ca2 -binding sites. Three globular domains extend from the cytoplasmic side: the N (nucleotide-binding) domain has the binding site for ATP; the P (phosphorylation) domain contains the Asp351 residue (blue) that undergoes reversible phosphorylation, and the A (actuator) domain som...
ular space (a) MsbA (b) BtuCD FIGURE 11–41 Structures of two ABC transporters of E. coli. (a) The lipid A flippase MsbA (PDB ID 1JSQ) and (b) the vitamin B12 importer BtuCD (PDB ID 1L7V). Both structures are homodimers. The two nucleotidebinding domains (NBDs, in red) extend into the cytoplasm. In (b), residues involve...
pump lactose against a concentration gradient (Fig. 11–42b). The balance between the two conformations of the lactose transporter is affected by changes in charge pairing between side chains. In intestinal epithelial cells, glucose and certain amino acids are accumulated by symport with Na, down the Na gradient establi...
Allow Rapid Movement of Ions across Membranes Ion-selective channels —first recognized in neurons and now known to be present in the plasma membranes of all cells, as well as in the intracellular membranes of eukaryotes—provide another mechanism for moving inorganic ions across membranes. Ion channels, together with io...
ty. The Neuronal Na Channel Is a Voltage-Gated Ion Channel Sodium ion channels in the plasma membranes of neurons and of myocytes of heart and skeletal muscle sense 8885d_c11_369-420 2/7/04 6:58 AM Page 411 mac76 mac76:385_reb: 11.3 Solute Transport across Membranes 411 Inactivation of the channel is thought to occur b...
nitine transporter of mitochondrial 17–6 phosphorylation, and exports product ATP Imports fatty acids into matrix for oxidation inner membrane Pi-H symporter of mitochondrial inner membrane Malate–-ketoglutarate transporter of mitochondrial inner membrane Glutamate-aspartate transporter of mitochondrial 19–27 inner mem...
ions and carry them passively across membranes, dissipating the energy of electrochemical ion gradients. ■ Water moves across membranes through aquaporins. ■ Ion channels provide hydrophilic pores through which select ions can diffuse, moving down their electrical or chemical concentration gradients; they are character...
mL) Number of cells (per mm3) Total surface area of lipid monolayer from cells (m2) Total surface area of one cell (m2) 40 10 1 8,000,000 9,900,000 4,740,000 62 6.0 0.92 98 29.8 99.4 Animal Dog Sheep Human Source: Data from Gorter, E. & Grendel, F. (1925) On bimolecular layers of lipoids on the chromocytes of the blood...
olic activities taking place in different tissues, and, in an embryo, the correct placement of cells during development. In all these cases, the signal represents information that is detected by specific receptors and converted to a cellular response, which always involves a chemical process. This conversion of informa...
s hyperbolic, rising toward a maximum for [RL] as the receptor sites become saturated. To control for nonsaturable, nonspecific binding sites (eicosanoid hormones bind nonspecifically to the lipid bilayer, for example), a separate series of binding experiments is also necessary. A large excess of unlabeled hormone is a...
ential reaches 70 mV, the effect of this membrane potential (to resist further entry of Na) exactly equals the effect of the Na concentration gradient (to cause more Na to flow inward). At this equilibrium potential (E), the driving force (G) tending to move an ion is zero. The equilibrium potential is different for ea...
he cation channel is converted to an anion channel. Depending on which ion passes through a channel, the ligand (neurotransmitter) for that channel either depolarizes or hyperpolarizes the target cell. A single neuron normally receives input from several (or many) other neurons, each releasing its own characteristic ne...
ce a 30 Å change in the position of the activation loop, away from the substrate-binding site, which becomes available to bind to and phosphorylate a target protein, shown here as a red arrow. Grb2 is not the only protein that associates with phosphorylated IRS-1. The enzyme phosphoinositide 3kinase (PI-3K) binds IRS-1...
by intracellular nitric oxide (NO); this form is found in many tissues, including smooth muscle of the heart and blood vessels. Cyclic GMP is a second messenger that carries different messages in different tissues. In the kidney and intestine it triggers changes in ion transport and water retention; in cardiac muscle ...
smitter in adrenergic neurons. Its affinity for its receptor is expressed as a dissociation constant for the receptor-ligand complex. Isoproterenol and propranolol are synthetic analogs, one an agonist with an affinity for the receptor that is higher than that of epinephrine, and the other an antagonist with extremely ...
molecules of the target protein—phosphorylase b kinase in Figure 12–16. This Adenosine 5-monophosphate (AMP) OH OH The intracellular signal therefore persists only as long as the hormone receptor remains occupied by epinephrine. Methyl xanthines such as caffeine and theophylline (a component of tea) inhibit the phospho...
catalyzes GTP-GDP exchange on an associated G protein, Gq (step 2 ), activating it exactly as the -adrenergic receptor activates Gs (Fig. 12–12). The activated Gq in turn activates a specific membrane-bound PLC (step 3 ), which catalyzes the production of the two second messengers diacylglycerol and IP3 by hydrolysis ...
hibit it through Gi. Thus cellular [cAMP] reflects the integrated input of two (or more) signals. ■ Cyclic AMP is eventually eliminated by cAMP phosphodiesterase, and Gs turns itself off by hydrolysis of its bound GTP to GDP. When the epinephrine signal persists, -adrenergic receptor–specific protein kinase and arresti...
nces in the structure of SH2 domains in different proteins account for the specificities of their interactions with various P –Tyr-containing proteins. The three to five residues on the carboxyl-terminal side of the P –Tyr residue are critical in determining the specificity of interactions with SH2 domains (Fig. 12–22)...
stration of signaling proteins is functionally significant. When cholesterol is removed from rafts by treatment with cyclodextrin (which binds cholesterol and removes it from membranes), the rafts are disrupted and a number of signaling pathways become defective. How might localization in rafts influence signaling thro...
e receptors Trimeric G proteins PI-specific phospholipase C Tyrosine kinase receptors SH2 domains Nuclear steroid receptors Protein kinase A Protein kinase G / / ? ? ? ? ? ? ? ? 8885d_c12_454 2/20/04 1:25 PM Page 454 mac76 mac76:385_reb: 454 Chapter 12 Biosignaling Plants COO Animals O 8 12 O OH HO Jasmonate Prostaglan...
can discriminate colors. Both cell types are long, narrow, specialized sensory neurons with two distinct cellular compartments: the outer segment contains dozens of membranous disks loaded with the membrane protein rhodopsin, and the inner segment contains the nucleus and many mitochondria, which produce the ATP essen...
nd [Ca2] declines (step 8885d_c12_459 2/20/04 1:26 PM Page 459 mac76 mac76:385_reb: 12.7 Sensory Transduction in Vision, Olfaction, and Gustation 459 1 Light absorption converts 11-cisretinal to all-trans-retinal, activating rhodopsin. 2 Activated rhodopsin catalyzes replacement of GDP by GTP on transducin (T), which t...
lf), causing its dissociation into a and bg. 3 Ga-GTP activates adenylyl cyclase, which catalyzes cAMP synthesis, raising [cAMP]. 4 cAMP-gated cation channels open. Ca2+ enters, raising internal [Ca2+]. Air Mucous layer O OR Golf b g a GDP GDP GTP 7 Golf hydrolyzes GTP to GDP, shutting itself off. PDE hydrolyzes cAMP. ...
er either an increase in [cAMP] (by activating adenylyl cyclase) or an increase in [Ca2] (by activating PLC). These second messengers affect ion channels and thus the Vm. ■ Gustatory neurons have serpentine receptors that respond to tastants by altering [cAMP], which in turn changes Vm by gating ion channels. ■ There i...
s activation. (a) Without cyclin (PDB ID 1HCK), CDK2 folds so that one segment, the T loop (red), obstructs the binding site for protein substrates and thus inhibits protein kinase activity. The binding site for ATP (blue) is also near the T loop. (b) When cyclin binds (PDB ID 1FIN), it forces conformational changes th...
which it was discovered, pRb functions in most, perhaps all, cell types to regulate cell division in response to a variety of stimuli. Unphosphorylated pRb binds the transcription factor E2F; while bound to pRb, E2F cannot promote transcription of a group of genes necessary for DNA synthesis (the genes for DNA polymera...
cancer syndrome, in which multiple cancers (of the breast, brain, bone, blood, lung, and skin) occur at high frequency and at an early age. The explanation for multiple tumors in this case is the same as that for Rb mutations: an individual born with one defective copy of p53 in every somatic cell is likely to suffer ...
r, L. & Friedrich, P. (eds) (2001) Protein Modules in Cellular Signalling, IOS Press, Washington, DC. Receptor Ion Channels See also Chapter 11, Further Reading, Ion Channels. Aidley, D.J. & Stanfield, P.R. (1996) Ion Channels: Molecules in Action, Cambridge University Press, Cambridge. Clear, concise introduction to t...
. Brief, intermediate-level review. 8885d_c12_477 2/20/04 1:31 PM Page 477 mac76 mac76:385_reb: Chapter 12 Problems 477 Jordan, V.C. (1998) Designer estrogens. Sci. Am. 279 (October), 60–67. Morgan, D.O. (1997) Cyclin-dependent kinases: engines, clocks, and microprocessors. Annu. Rev. Cell Dev. Biol. 13, 261–291. Intro...
jection EGTA (ethylene glycol-bis(-aminoethyl ether)-N,N,N,N-tetraacetic acid) is a chelating agent with high affinity and specificity for Ca2. By microinjecting a cell with an appropriate Ca2-EDTA solution, an experimenter can prevent cytosolic [Ca2] from rising above 107 M. How would EGTA microinjection affect a cell...
are used in anabolic pathways to convert small precursor molecules into cell macromolecules. Part II Bioenergetics and Metabolism 483 simultaneous synthesis and degradation of fatty acids would be wasteful, however, and this is prevented by reciprocally regulating the anabolic and catabolic reaction sequences: when on...
a carbanion on an adjoining carbon, because the carbonyl group can delocalize electrons through resonance (Fig. 8a, b). The importance of a carbonyl group is evident in three major classes of reactions in which COC bonds are formed or broken (Fig 8c): aldol condensations (such as the aldolase reaction; see Fig. 14–5), ...
trochemical potential, produced either by substrate oxidation or by light absorption, drives the synthesis of ATP. Chapters 20 through 22 describe the major anabolic pathways by which cells use the energy in ATP to produce carbohydrates, lipids, amino acids, and nucleotides from simpler precursors. In Chapter 23 we ste...
pical of favorable processes, tend to make G negative. In fact, G of a spontaneously reacting system is always negative. The second law of thermodynamics states that the entropy of the universe increases during all chemical and physical processes, but it does not require that the entropy increase take place in the reac...
in which direction and how far a given reaction must go to reach equilibrium when the initial concentration of each component is 1.0 M, the pH is 7.0, the temperature is 25 C, and the pressure is 101.3 kPa. Thus G is a constant: it has a characteristic, unchanging value for a given reaction. But the actual free-energy...
hange that is the sum of the G values for the individual reactions. ■ 496 Chapter 13 Principles of Bioenergetics 13.2 Phosphoryl Group Transfers and ATP Having developed some fundamental principles of energy changes in chemical systems, we can now examine the energy cycle in cells and the special role of ATP as the ene...
red to synthesize ATP from ADP and Pi under the conditions prevailing in the erythrocyte would be 52 kJ/mol. Because the concentrations of ATP, ADP, and Pi differ from one cell type to another (see Table 13–5), Gp for ATP hydrolysis likewise differs among cells. Moreover, in any given cell, Gp can vary from time to tim...
actants. For simplicity, we will sometimes use the term “high-energy phosphate compound” when referring to ATP or other phosphate compounds with a large, negative, standard free energy of hydrolysis. As is evident from the additivity of free-energy changes of sequential reactions, any phosphorylated compound can be syn...
measure minute quantities of ATP by the intensity of the light flash produced. As little as a few picomoles (1012 mol) of ATP can be measured in this way. An enlightening extension of the studies in luciferase was the cloning of the luciferase gene into tobacco plants. When watered with a solution containing luciferin,...
volcanic condensates and steam vents suggests that it could have served as an energy source in prebiotic and early cellular evolution. In prokaryotes, the enzyme polyphosphate ki- nase-1 (PPK-1) catalyzes the reversible reaction ATP polyPn Mg2 3:::4 ADP polyPn1 DG 20 kJ/mol by a mechanism involving an enzyme-bound pho...
t pair (redox pair), just as an acid and corresponding base function as a conjugate acid-base pair. Recall from Chapter 2 that in acidbase reactions we can write a general equation: proton donor 34 H proton acceptor. In redox reactions we can write a similar general equation: electron donor 34 e electron acceptor. In t...
the standard hydrogen electrode, their reduction potentials relative to each other are also known. We can then predict the direction in which electrons will tend to flow when the two half-cells are connected through an external circuit or when components of both half-cells are present in the same solution. Electrons te...
bsorption band with a maximum at 340 nm. The production of NADH during an enzyme-catalyzed reaction can be conveniently followed by observing the appearance of the absorbance at 1). 340 nm (the molar extinction coefficient 6,200 M 1cm 340 amino acids occur in the mitochondrial matrix, whereas reductive biosynthesis pro...
N N N N H OH Flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) OH Flavoproteins are often very complex; some have, in addition to a flavin nucleotide, tightly bound inorganic ions (iron or molybdenum, for example) capable of participating in electron transfers. Certain flavoproteins act in a quite diff...
e, N.C. (2002) New uses for an old enzyme—the old yellow enzyme family of flavoenzymes. Microbiology 148, 1607–1614. lowing reactions at pH 7.0 and 25 C, using the G values in Table 13–4. (a) Glucose 6-phosphate H2O glucose 6-phosphatase 3::::::::::4 glucose Pi (b) Lactose H2O b-galactosidase 3::::::::::4 glucose galac...
action? 19. Energy Span of the Respiratory Chain Electron transfer in the mitochondrial respiratory chain may be represented by the net reaction equation NADH H 1 O2 34 H2O NAD 2 (a) Calculate the value of E for the net reaction of mitochondrial electron transfer. Use E values from Table 13–7. (b) Calculate G for this ...
hase of glycolysis. From a chemical perspective, the isomerization in step 2 is critical for setting up the phosphorylation and COC bond cleavage reactions in steps 3 and 4 , as detailed later. Note that two molecules of ATP are invested before the cleavage of glucose into two three-carbon pieces; later there will be a...
hey added blood serum (known to contain inhibitors of proteolytic enzymes) to yeast extracts and observed the predicted stimulation of glucose metabolism. However, in a control experiment intended to show that boiling the serum destroyed the stimulatory activity, they discovered that boiled serum was just as effective ...
acid residues that serve as general acid (A) or base (B). and stabilizes the enolate intermediate created in the COC bond cleavage step. Although the aldolase reaction has a strongly positive standard free-energy change in the direction of fructose 1,6-bisphosphate cleavage, at the lower concentrations of reactants pre...
from a substrate such as 1,3-bisphosphoglycerate is referred to as a substrate-level phosphorylation, to distinguish this mechanism from respiration-linked phosphorylation. Substrate-level phosphorylations involve soluble enzymes and chemical intermediates (1,3-bisphosphoglycerate in this case). Respiration-linked pho...
nzymes of glycolysis. In these studies he developed and used an experimental tool that revolutionized biochemical studies of oxidative metabolism: the Warburg manometer, which measured directly the consumption of oxygen by monitoring changes in gas volume, and therefore allowed quantitative measurement of any enzyme wi...
hosphate ADP Thus both products of fructose 1-phosphate hydrolysis enter the glycolytic pathway as glyceraldehyde 3phosphate. D-Galactose, a product of hydrolysis of the disaccharide lactose (milk sugar), passes in the blood from the intestine to the liver, where it is first phosphorylated at C-1, at the expense of ATP...

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