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The second local factor is pollution. A lot had been done to bring the subject to people's attention to the point where we think about it as enormous disasters attached to super fun cleanup sites and such, but there are other more subtle ways of polluting the environment, which I think are worth thinking about when we ... | Human activities that threaten biodiversity.mp3 |
Waterborne pollutants can pop out in very unusual places and have really big downstream effects, if you'll excuse the pun, on the reproductive viability of organisms that happen to be in those places. There are also dead zones in the ocean caused by nitrogen fertilizers that wash into rivers. Where the rivers flow into... | Human activities that threaten biodiversity.mp3 |
Anything that tries to be active in an area where the oxygen is being used up by the bacteria, any oxygen requiring organism, that is pretty much any animal for example, is going to have a really hard time of it. These dead zones are now starting to be a little bit better understood and it's pretty clear that they're g... | Human activities that threaten biodiversity.mp3 |
Untreated sewage is a classic problem for biodiversity. It's not just, of course, human waste. It has to do with sometimes bizarre chemistry involved in the high-tech stuff that we're making now. We're talking about chemical compounds, including drugs and PCBs. There are lots of strange molecules that humans are produc... | Human activities that threaten biodiversity.mp3 |
We're talking about chemical compounds, including drugs and PCBs. There are lots of strange molecules that humans are producing and dumping. In some cases, you get these hormone mimics, simple compounds derived from prescription drugs and other man-made chemicals that get flushed into waterways. Hormone mimics act like... | Human activities that threaten biodiversity.mp3 |
Hormone mimics act like naturally occurring hormones that control normal development of wild organisms, particularly water-living ones. Hormone mimics can also adversely affect their reproductive organs. There are many, many, many examples of this kind of pollution, one that people wouldn't necessarily think of. Anothe... | Human activities that threaten biodiversity.mp3 |
Another one that doesn't immediately occur to people is noise pollution. Birds in cities are reacting to noise levels. Even the organisms that are not being wiped out because of our expanding cities are starting to adapt to an urban environment by changing their behavior and reproductive patterns. And some of them just... | Human activities that threaten biodiversity.mp3 |
And some of them just can't do it. Noise can also be a major factor in marine mammal survival. Evidence suggests that sonar pollution interferes with the health of marine mammals. Patterns of reproduction can also be upset by our introduction of light pollution to places where there wasn't light before. Sea turtle hatc... | Human activities that threaten biodiversity.mp3 |
Patterns of reproduction can also be upset by our introduction of light pollution to places where there wasn't light before. Sea turtle hatchlings can be impacted by artificial light heading toward it instead of the ocean when they hatch out of their nests on the beach. And bird strikes on buildings are greatly increas... | Human activities that threaten biodiversity.mp3 |
Let's look at the third local factor, resource exploitation. This gets to the simple idea that humans are always using things from their environment. We are inextricably linked to that environment and we use up stuff. We always have. We have to do that in order to stay alive. There are classic ways we use resources lik... | Human activities that threaten biodiversity.mp3 |
We always have. We have to do that in order to stay alive. There are classic ways we use resources like hunting, cutting down forests for firewood and lumber. Where does the biodiversity go then? A big one for me as a marine scientist, of course, is fishing. We talk about the harvest of fish, but it's not really a gath... | Human activities that threaten biodiversity.mp3 |
Where does the biodiversity go then? A big one for me as a marine scientist, of course, is fishing. We talk about the harvest of fish, but it's not really a gathering of what one sows. It's really a straight up removal of a resource as much as mining is. There are attempts to control overfishing, but to a large extent ... | Human activities that threaten biodiversity.mp3 |
It's really a straight up removal of a resource as much as mining is. There are attempts to control overfishing, but to a large extent we often don't have enough data to know just what a sustainable amount of extraction is until it's too late. Before we were moved to action, for example, the cod fishery had collapsed o... | Human activities that threaten biodiversity.mp3 |
For example, someone might have told you, hey, you walk kind of like your dad, or your smile is kind of like your mom, or your eyes are like one of your uncles or your grandparents. And so there's always been this notion of inherited traits. But it wasn't until the 1800s that that started to be studied in a more scient... | DNA Biomolecules MCAT Khan Academy.mp3 |
But even then, even Mendel, who was starting to understand the mechanisms of, or he was trying to understand how inheritance happens, and he even could start to breed certain types of things, even he didn't know exactly what was the molecular basis for inheritance. And the answer to that question wasn't figured out unt... | DNA Biomolecules MCAT Khan Academy.mp3 |
But it was really the structure of DNA that made people say, hey, that looks like the molecule that's storing the information. And just to be clear, DNA wasn't discovered in 1953. DNA was discovered in the mid-1800s. It was this kind of, this molecule that was inside of nuclei, of cells, and for some time, people said,... | DNA Biomolecules MCAT Khan Academy.mp3 |
It was this kind of, this molecule that was inside of nuclei, of cells, and for some time, people said, oh, maybe this could be a molecular basis of inheritance. You know, you could imagine what you would need to be a molecular basis of inheritance. It would have to be a molecule or a series of molecules that could con... | DNA Biomolecules MCAT Khan Academy.mp3 |
But it wasn't until 1953, when this double helix structure of DNA was established that people said, hey, this looks like our molecule. So first, let's just talk about the structure here, and then actually we'll talk about where this name, DNA, deoxyribonucleic acid, comes from. And then we'll talk a little bit about wh... | DNA Biomolecules MCAT Khan Academy.mp3 |
We might go in-depth on the expression of information in future videos. So this structure right over here, and this is a visual depiction of a DNA molecule, you can view this as kind of a twisted ladder. It has these two, I guess you could say, sides of the ladder that are twisted. That is one side right over there, an... | DNA Biomolecules MCAT Khan Academy.mp3 |
That is one side right over there, and then it is another side. There is another side right over here. And in between those two sides, or connecting those two sides of that twisted ladder, you have these rungs. And these rungs are actually where the information, the genetic information is, I guess you could say, stored... | DNA Biomolecules MCAT Khan Academy.mp3 |
And these rungs are actually where the information, the genetic information is, I guess you could say, stored in some way. Because these rungs, it's a sequence of different bases. And when I say bases, you might say, wait, this says acid, why are you saying bases right over here? Well, the word deoxyribonucleic acid co... | DNA Biomolecules MCAT Khan Academy.mp3 |
Well, the word deoxyribonucleic acid comes from the fact that this backbone is made up of a combination of sugar and phosphate. And the sugar that makes up the backbone is deoxyribose, so that's essentially the D in DNA. And then the phosphate group is acidic, and that's where you get the acid part of it. And nucleic i... | DNA Biomolecules MCAT Khan Academy.mp3 |
And nucleic is, hey, this was found in nuclei of cells. It is nucleic acid, deoxyribonucleic acid. But it's not, it also, it is actually mildly acidic all in total, but for every acid, it actually also has a base. And that base, those bases form the rung of the ladders. And actually, each rung is a pair of bases. And a... | DNA Biomolecules MCAT Khan Academy.mp3 |
And that base, those bases form the rung of the ladders. And actually, each rung is a pair of bases. And as I said, that's where the information is actually stored. Well, what am I talking about? Well, let me talk about the four different bases that make up the rungs of a DNA molecule. So you have adenine. And so, for ... | DNA Biomolecules MCAT Khan Academy.mp3 |
Well, what am I talking about? Well, let me talk about the four different bases that make up the rungs of a DNA molecule. So you have adenine. And so, for example, this part right over here, this section of that rung might be adenine. Maybe this right over here is adenine. This right over here. Remember, each of these ... | DNA Biomolecules MCAT Khan Academy.mp3 |
And so, for example, this part right over here, this section of that rung might be adenine. Maybe this right over here is adenine. This right over here. Remember, each of these rungs are made up by, it's a pair of bases. And that might be adenine. Maybe this is adenine. And I could stop there. | DNA Biomolecules MCAT Khan Academy.mp3 |
Remember, each of these rungs are made up by, it's a pair of bases. And that might be adenine. Maybe this is adenine. And I could stop there. I'll do a little more adenine. Maybe that's adenine right over there. And adenine always pairs with the base thymine. | DNA Biomolecules MCAT Khan Academy.mp3 |
And I could stop there. I'll do a little more adenine. Maybe that's adenine right over there. And adenine always pairs with the base thymine. So let me write that down. So adenine pairs with thymine. Thymine. | DNA Biomolecules MCAT Khan Academy.mp3 |
And adenine always pairs with the base thymine. So let me write that down. So adenine pairs with thymine. Thymine. So if that's an adenine there, then this is going to be a thymine. If this is an adenine, then this is going to be a thymine. Or if I drew the thymine first, well, I'll say, okay, it's going to pair with t... | DNA Biomolecules MCAT Khan Academy.mp3 |
Thymine. So if that's an adenine there, then this is going to be a thymine. If this is an adenine, then this is going to be a thymine. Or if I drew the thymine first, well, I'll say, okay, it's going to pair with the adenine. So this is going to be a thymine right over here. This is going to be a thymine. If I were to ... | DNA Biomolecules MCAT Khan Academy.mp3 |
Or if I drew the thymine first, well, I'll say, okay, it's going to pair with the adenine. So this is going to be a thymine right over here. This is going to be a thymine. If I were to draw this, this would be a thymine right over here. Now, the other two bases, you have cytosine, which pairs with guanine, or guanine t... | DNA Biomolecules MCAT Khan Academy.mp3 |
If I were to draw this, this would be a thymine right over here. Now, the other two bases, you have cytosine, which pairs with guanine, or guanine that pairs with cytosine. So guanine. And we're not going to go into the molecular structure of these bases just yet, although these are good names to know because they show... | DNA Biomolecules MCAT Khan Academy.mp3 |
And we're not going to go into the molecular structure of these bases just yet, although these are good names to know because they show up a lot and they really form kind of the code, your genetic code. So guanine pairs with cytosine. Guanine and cytosine. Cytosine. So actually, if this is, let's say there's some cytos... | DNA Biomolecules MCAT Khan Academy.mp3 |
Cytosine. So actually, if this is, let's say there's some cytosine there, let's say cytosine right over here, maybe this is cytosine, maybe this is cytosine, maybe this is cytosine, this is cytosine, and maybe this is cytosine, then it always pairs with the guanine. If we're talking about, so let's see, this is guanine... | DNA Biomolecules MCAT Khan Academy.mp3 |
Actually, just to make it a little bit more complete, let me just color in the rungs here as best as I can. So those are guanine, so they're gonna pair with cytosine, pair with cytosine, pair with cytosine. And when it's drawn this way, you might start to see how this is essentially a code, the order of which the bases... | DNA Biomolecules MCAT Khan Academy.mp3 |
It is because that information, to a large degree, is encoded genetically. It affects a lot of what makes you you, and actually not even just within a species, but also across species. Humans have more genetic material in common with other humans than they do with, say, a plant, but all living creatures as we know them... | DNA Biomolecules MCAT Khan Academy.mp3 |
This is the basis by which they are passing down their actual traits. Now, you might be saying, well, how much genetic information does a human being have? And the number will either disappoint you or you might find it mind-boggling. The human genome, and every species has a different number of base pairs, to a large d... | DNA Biomolecules MCAT Khan Academy.mp3 |
The human genome, and every species has a different number of base pairs, to a large degree correlated with how complex they are, although not always, but the human genome has six million, sorry, not six million, six billion. Six million would be disappointing. Even billion might be disappointing. Six billion base pair... | DNA Biomolecules MCAT Khan Academy.mp3 |
Six billion base pairs. Six billion base pairs. And when you have your full complement of chromosomes, and this is in most of the cells in your body, outside of your sex cells, the sperm or the egg cells, this is going to be spread over 46 chromosomes. 46 chromosomes, or I guess you could say 23 pair of chromosomes. So... | DNA Biomolecules MCAT Khan Academy.mp3 |
46 chromosomes, or I guess you could say 23 pair of chromosomes. So if you divide six billion by 46, you get a little over, on average, 100 million, I think it's 100 and something million base pairs per chromosome. And some chromosomes are longer, actually some of the longest are over 200 million, and some might be sho... | DNA Biomolecules MCAT Khan Academy.mp3 |
That's just on average. Now, this number might, to some of you, might be exciting. You're like, oh, I thought I was a simple creature. I didn't know I was this complex. Six billion, that's a lot of base pairs. That feels like a lot of information. For others of you, it might not feel so great. | DNA Biomolecules MCAT Khan Academy.mp3 |
I didn't know I was this complex. Six billion, that's a lot of base pairs. That feels like a lot of information. For others of you, it might not feel so great. You might say, hey, wait, I could store this much information on a modern thumb drive or on a hard disk. I thought I was more unique than that. And of course, w... | DNA Biomolecules MCAT Khan Academy.mp3 |
For others of you, it might not feel so great. You might say, hey, wait, I could store this much information on a modern thumb drive or on a hard disk. I thought I was more unique than that. And of course, we all are special and unique, but you might say, oh, six billion base pairs, I thought I was infinitely complex a... | DNA Biomolecules MCAT Khan Academy.mp3 |
And of course, we all are special and unique, but you might say, oh, six billion base pairs, I thought I was infinitely complex and whatever else, and there's some arguments for that along some other directions. But this is the approximate length, I guess you could say, the approximate size of the actual human genome. ... | DNA Biomolecules MCAT Khan Academy.mp3 |
We have about 20 base pairs depicted here. Imagine if you had about 200 million of these base pairs, and then you were to take this thing and you were to kind of coil it up into that thing is a chromosome. Is a chromosome. And you're saying, wait, I have that much information in most of the cells of my body? This thing... | DNA Biomolecules MCAT Khan Academy.mp3 |
And you're saying, wait, I have that much information in most of the cells of my body? This thing must be incredibly compact. And if you said that, I would say, yes, you are correct. This, the radius, the radius of the DNA molecule is on the order of one nanometer. One nanometer, which is a billionth of a meter. So you... | DNA Biomolecules MCAT Khan Academy.mp3 |
This, the radius, the radius of the DNA molecule is on the order of one nanometer. One nanometer, which is a billionth of a meter. So you can start to assess kind of the scale of this thing. This is a very dense way to actually store information. But just to have an appreciation of, and you might have seen it when I wa... | DNA Biomolecules MCAT Khan Academy.mp3 |
This is a very dense way to actually store information. But just to have an appreciation of, and you might have seen it when I was coloring in, on why the structure lends itself to being able to replicate the information or even to be able to translate or express the information, let's think about if you were to take t... | DNA Biomolecules MCAT Khan Academy.mp3 |
So you essentially have half of the ladder. And so if you only have half of the ladder, you're able to construct the other half of the ladder. Let's take an example. Let's say, and I'll just use the first letter to abbreviate for each of these bases. So let's say you have some, so let's say this is one of the, this is ... | DNA Biomolecules MCAT Khan Academy.mp3 |
Let's say, and I'll just use the first letter to abbreviate for each of these bases. So let's say you have some, so let's say this is one of the, this is the sugar phosphate backbone right over here. So this could be one of the sides. And let's say there's some adenine, actually, let me do them in the right color. So y... | DNA Biomolecules MCAT Khan Academy.mp3 |
And let's say there's some adenine, actually, let me do them in the right color. So you've got some adenine, adenine, maybe some adenine right over here. Maybe there's an adenine there. Maybe you have some thymine, thymine, maybe thymine right over here. Then you have some, you have some guanine, guanine, guanine. And ... | DNA Biomolecules MCAT Khan Academy.mp3 |
Maybe you have some thymine, thymine, maybe thymine right over here. Then you have some, you have some guanine, guanine, guanine. And then let's say you have some cytosine and you have some cytosine. So with just half of this ladder, I guess you could say, you're able to construct the other half. And that's actually ho... | DNA Biomolecules MCAT Khan Academy.mp3 |
So with just half of this ladder, I guess you could say, you're able to construct the other half. And that's actually how DNA replicates. This ladder splits and then each of those two halves of that ladder are able to construct versions of the other half, or versions of the other half are able to be constructed on top ... | DNA Biomolecules MCAT Khan Academy.mp3 |
So how does that happen? Well, it's based on how these bases pair. Adenine always pairs with thymine if we're talking about DNA. So if you have an A there, you're gonna have a T on this end, T on this end. T's right all over here, T right over there. If you have a T on that end, you're gonna have an A right over there,... | DNA Biomolecules MCAT Khan Academy.mp3 |
So if you have an A there, you're gonna have a T on this end, T on this end. T's right all over here, T right over there. If you have a T on that end, you're gonna have an A right over there, A, A. If you have a G, a guanine on this side, you're gonna have a cytosine on the other side. Cytosine, cytosine, cytosine. And... | DNA Biomolecules MCAT Khan Academy.mp3 |
If you have a G, a guanine on this side, you're gonna have a cytosine on the other side. Cytosine, cytosine, cytosine. And if you have a cytosine, you're gonna have a guanine on the other side. And so hopefully that gives you an appreciation of how DNA can replicate itself. And as we'll see also, how this information c... | DNA Biomolecules MCAT Khan Academy.mp3 |
And so hopefully that gives you an appreciation of how DNA can replicate itself. And as we'll see also, how this information can be translated to other forms of either related molecules, but eventually to proteins. And just to kind of round out this video, to get a real visual sense of what the DNA molecule looks like,... | DNA Biomolecules MCAT Khan Academy.mp3 |
So let's stick with this idea, this simplification, that there's a gene for eye color, and it only comes with two variants. It has the dominant variant, which codes for brown eye color, and it has the recessive variant, which codes for blue eye color. So if either one of your alleles is this capital B, you're gonna hav... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
The only way to have blue eyes is to have lowercase, is to be homozygous for the recessive allele. Now let's say that in a population, it's a large population, one that meets all of the Hardy-Weinberg equilibrium assumptions, let's say that you were to observe that 9% of this population has blue eyes. So now we're talk... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
You can actually observe that they have blue eyes. So based on this, can we figure out, can we figure out P, which is the frequency of the dominant allele, can we figure this out? And can we figure out Q, which is the frequency of the recessive allele, can we figure that out as well? And I encourage you to pause this v... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
And I encourage you to pause this video, and based on what we saw of the Hardy-Weinberg equation, can we figure these things out, given this information? Well, let's revisit the Hardy-Weinberg equation. We've worked it out in a previous video, but I'll rewrite it right now. It says the allele frequency for the dominant... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
It says the allele frequency for the dominant, the dominant allele frequency squared plus two times the dominant allele frequency times the recessive allele frequency plus the recessive allele frequency squared is equal to one. And we saw that this just comes from the idea that P plus Q is going to be equal to one. The... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Now, when we say 9% has blue eyes, what does that mean? Well, the only way to have blue eyes is if your genotype is homozygous recessive, because if you have a capital B in here, then you're gonna have brown eyes. So we can say that 9% also has this genotype. Or you could say that the frequency in the population of thi... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Or you could say that the frequency in the population of this genotype is 9%. But we've already seen that's exactly, that's exactly what this term right over here is. That's this Q squared term. This is the probability, one way to think about it, of getting, of, this is the, Q, of course, is the frequency of the recess... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
This is the probability, one way to think about it, of getting, of, this is the, Q, of course, is the frequency of the recessive allele. Now, this is the, you could view this as the probability of getting two of the recessive alleles is going to be, if you're in your population, it's going to be 9%. So we could say Q s... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Or another way to think about it, this term right over here is 9%, or 0.09, 0.09. That's what this, 9% has this genotype, that's what this tells us right over here. So then we can solve for Q. If Q squared, I'll write it as a decimal, 0.09, that means that Q is going to be the square root of 0.09, which is equal to 0.3... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
If Q squared, I'll write it as a decimal, 0.09, that means that Q is going to be the square root of 0.09, which is equal to 0.3. So just like that, we were able to figure out the allele frequency of the recessive allele. 30%, and I could write that as a percentage, 0.3, or 30%, if you were looking at the genes in the p... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
And so based on that, we can figure out what percentage code for the dominant variant. The rest of the genes must code for the dominant one, because we're assuming there's only two of them. P plus Q equal 100%, or P plus Q is equal to one. So this must be 70%. So just based on that, we can kind of dig a little bit deep... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
So this must be 70%. So just based on that, we can kind of dig a little bit deeper here. So what is P squared? P squared is going to be 70% squared, or 0.7 squared. So this right over here is 0.7 squared, which is 0.49. So one way to think about it is, based on this, and once again, a lot of simple equation, but these ... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
P squared is going to be 70% squared, or 0.7 squared. So this right over here is 0.7 squared, which is 0.49. So one way to think about it is, based on this, and once again, a lot of simple equation, but these really neat ideas are starting to pop out of it. Based on just this information, we're now able to say that 49%... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Based on just this information, we're now able to say that 49% of the population is going to have a genotype of capital B, capital B. They're gonna be homozygous dominant. And then we can figure out this right over here. Two times P times Q, that's going to be two times 0.7, times 0.7, times 0.3, times 0.3. So let's se... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Two times P times Q, that's going to be two times 0.7, times 0.7, times 0.3, times 0.3. So let's see, that's going to be two times 0.21, so this is going to be, this right over here is going to be 0.42. Or another way to think about it is, 42% of this population is going to have the genotype uppercase B and lowercase b... | Applying the Hardy-Weinberg equation Biomolecules MCAT Khan Academy.mp3 |
Let's say that you have decided to go canoeing and right over here, this is a top view of our river right here. This is our river and let's say that the current, the river is going towards the right. So there's two different directions. So there's two different directions that you could be canoeing in. You could imagin... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
So there's two different directions that you could be canoeing in. You could imagine someone who is canoeing in the same direction as the current, so they are canoeing that way, and then you could imagine another person who's canoeing the other way. So someone who's canoeing upstream. This person is canoeing downstream... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
This person is canoeing downstream, this person is canoeing upstream, so they are going in that direction. So pause this video and think about which person is going to have to expend more energy or which person is going to have to be more active and which person is going to be more passive. Well, yes, this wasn't an in... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
If you are going with the flow of current, as the person in yellow is here, they don't even have to take their paddles out. They can just take a nap, and the boat will naturally go with the current. They would be, they could be just moving passively, while the person in blue here, they're gonna have to work really, rea... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
They're gonna have to paddle some just to not even move to the right, and then even paddle even more to actually go against the current. So this person would have to be very active. And so this is really just a metaphor for what we're going to talk about now, and that's the idea in biology of active versus passive tran... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
So let's start with maybe the more pleasant one in either situation, and that is passive transport. So passive transport is when something goes with the gradient. So what do I mean by that? So you could have a concentration gradient. So let's say that on, let's say I have a tube of some kind, and let's say it's filled ... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
So you could have a concentration gradient. So let's say that on, let's say I have a tube of some kind, and let's say it's filled with water, and dissolved in that water at this end of the tube, I have a high concentration of some molecule or something right over here, while on the right-hand side, I have a low concent... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
Well, these things are just going to naturally move around, and over time, they're gonna bounce their way so that after a little bit of time has passed, a lot of these things are just going to passively move to the right. And so at some point, you might have an equal concentration or roughly equal throughout this entir... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
This is a concentration gradient that we're moving along. Let me write that down. This is our concentration gradient. But you could also have an electrical gradient. So let's take a similar type of container. Maybe it's filled with water. And on the left-hand side, imagine if you have a bunch of positive particles or m... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
But you could also have an electrical gradient. So let's take a similar type of container. Maybe it's filled with water. And on the left-hand side, imagine if you have a bunch of positive particles or molecules, and on the right, you have a bunch of negative particles or molecules. Well, the positive ones repel each ot... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
And on the left-hand side, imagine if you have a bunch of positive particles or molecules, and on the right, you have a bunch of negative particles or molecules. Well, the positive ones repel each other, so do the negative ones, but the positives attract the negative, and the negative attract the positive. And so you w... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
The positives wanna go away from each other, and they are drawn to the negative. Similarly, the negatives wanna get away from each other, and they are drawn to the positive. So whether you're talking about a concentration gradient or an electrical gradient, and sometimes you have a combination of both, an electrochemic... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
So no energy needed. It's just going to happen naturally. Now, the opposite is the notion of active transport. Active transport. And this is when you go against the gradient. So an active transport would be somehow, let's say you're in this situation right over here, somehow getting one of these particles, let me do it... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
Active transport. And this is when you go against the gradient. So an active transport would be somehow, let's say you're in this situation right over here, somehow getting one of these particles, let me do it in that same color, somehow getting one of these particles, instead of moving to go in that direction, it will... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
Or another situation is, imagine if you have a positive particle right over here, instead of making it, instead of it naturally just going to that direction, somehow you make it go against its gradient, and you make it go closer to the other positive particles. Well, this is going to require energy to do. And probably ... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
But let's say that this thing that I'm drawing here in white, this is a cell membrane. And I'm drawing these gaps for a reason. And what you have on the outside of the cell membrane, you have some potassium ions on the outside, but you have a lot more on the inside. So these are all potassium ions on the inside of your... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
So these are all potassium ions on the inside of your cell. And then, so let me just write K plus, K plus, K plus, K plus, K plus. And you'll have some sodium ions on the inside of your cell, Na plus, but you have a lot more on the outside of your cell. And in general, the outside of your cell is going to have many mor... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
And in general, the outside of your cell is going to have many more positive ions than the inside. Maybe you already see where this is going. Na plus, Na plus, Na plus. I think you get the idea. Na plus, Na plus. Now, if on this membrane, let's ignore this part right over here. If I just had a channel right over here t... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
I think you get the idea. Na plus, Na plus. Now, if on this membrane, let's ignore this part right over here. If I just had a channel right over here that was open only to potassium, so only potassium can go through. So only potassium can go through this channel right over here. What do you think is going to happen? We... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
If I just had a channel right over here that was open only to potassium, so only potassium can go through. So only potassium can go through this channel right over here. What do you think is going to happen? Well, you would have passive transport. These positively charged potassiums right over here, they would go down ... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
Well, you would have passive transport. These positively charged potassiums right over here, they would go down their concentration gradient. There's more likely to have a potassium ion just bump in the right way just right over here so that it goes through the channel because there's just more potassiums out on the in... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
And so this, this potassium's going down their concentration gradient from high concentration to low concentration through this channel, this would be passive transport. Passive transport. But you could imagine there's also active transport. And that active transport is what pumps the sodium ions inside the cell outsid... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
And that active transport is what pumps the sodium ions inside the cell outside of the cell even though it's not only against its concentration gradient, it's also against its electrical gradient. The outside's more positive, so you wouldn't think a positive ion would naturally go outside. And the outside has more sodi... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
And as I hinted at, it does this using energy. So you'll sometimes see a sodium potassium pump drawn like this. And once again, I'm not gonna go into depth on it. We have a whole video on it. But the general idea is is that the sodiums bind over here and then some ATP, which is the powerhouse of cells, which we will st... | Introduction to passive and active transport High school biology Khan Academy.mp3 |
When we talk about the endocrine organs and the endocrine glands, and we talk about hormones flowing all throughout the body, it's pretty easy to develop this mental image of that process happening pretty haphazardly. And so you kind of imagine hormones just coursing all throughout the body, being fired at will and sen... | Hormone concentration metabolism and negative feedback NCLEX-RN Khan Academy.mp3 |
And so it turns out that the hormone concentration in our blood at any given time is pretty tightly controlled. And one of the ways that it's controlled is through this idea of metabolism and excretion. And so for every hormone that reaches its receptor, thousands more are swept up and removed by the body. And one of t... | Hormone concentration metabolism and negative feedback NCLEX-RN Khan Academy.mp3 |
And one of the ways that they're removed is through the liver. And the liver will metabolize extra hormones and turn them into bile, which is ultimately excreted in the digestive system. And another organ is the kidney. And you have two of these, and they're filtering your blood all of the time. And they're removing wa... | Hormone concentration metabolism and negative feedback NCLEX-RN Khan Academy.mp3 |
And you have two of these, and they're filtering your blood all of the time. And they're removing waste products from the blood through urine. And then some hormones are actually just broken down in the blood. And then the products of that breakdown flow into the liver or the kidneys. And then sometimes you can even sw... | Hormone concentration metabolism and negative feedback NCLEX-RN Khan Academy.mp3 |
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