Membrane Transport - Video Tutorials & Practice Problems
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concept
Membrane Transport Concept 1
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Now, when it comes to membrane transport, we're going to say that to perform its functions, a cell continuously needs to exchange substances with the extracellular fluid. So basically outside of itself, we're gonna say membrane transport allows cells to take in essential substances and expel waste products. Now, here when it comes to membrane transport mechanisms, they can be broadly cattery into two types. We have our passive transport and we have our active transport. We're gonna say here with passive transport, this does not require energy and substances move down the concentration gradient. But with active transport, we're gonna say it requires energy and substances move against the concentration gradient. So here we have our membrane transport which is broken down into passive transport and active transport. Active requires energy and with passive transport, it can be further broken down into simple diffusion and facilitated diffusion where we need some assistance for it to occur. Now here remember a concentration gradient. This is the difference in concentration of a substance over a distance. And we'll see how to distinguish between active and passive transport.
2
example
Membrane Transport Example 1
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Here, it says in the electron transport chain or etc complexes, 13 and four pump H plus ions from the mitochondrial matrix which has low hydrogen ion concentration to the inter membrane space where we have a high H plus ion concentration. What type of membrane transport is this? All right. So what's happening here? What we're taking H plus from an area where the concentration of H plus is low and we're pumping it to where it is high. This is the opposite of what we should expect because typically we would have the movement of ions from an area of low of high concentration to an area of low concentration. This is what passive transport would be here. We're doing the exact opposite we're taking where H pluses are low and pumping them somewhere where it's already high. There's gonna be a resistance there, which means we're gonna have to supply energy in order to do this because of that, this represents inactive transport. We're working against the concentration gradient. Again, normally we wanna go from high concentration to low concentration. But here the opposite is occurring, which means energy will be needed. So again, option A active transport would be the best answer.
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Problem
Problem
During respiration, oxygen gas diffuses into cells spontaneously. Which type of transport is this?
A
Active transport
B
Passive transport
C
Both
D
None of the above
4
concept
Membrane Transport Concept 2
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3m
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In this video, we'll take a look at different types of membrane transport mechanisms. Now, here we're going to say that nonpolar molecules, polar molecules and ions move across the cell membranes differently. And because of this, we need different types of mechanisms. The first one is simple diffusion here. This is the movement driven by concentration gradients. Here we're gonna say that small nonpolar molecules and water are involved. And we're gonna say examples would be oxygen co2 or steroids. If we take a look here, we're going to say if we say that this is the outside of the cell and this is the inside of the cell, we can see that these particles are just kind of going through the lipid bilayer, going from the outside here, going through the bilayer and winding up on the inside of the cell. This would represent passive or actually not pass it simple, simple the fusion. Next, we have facilitated diffusion. This is gradient driven and it's through a protein channel. Now, here we're gonna say this is dealing with polar molecules and ions. Examples would be glucose, water, chloride ion and bicarbonate. If we take a look here, we have our integral protein, which remember goes through the entire thickness of our lipid bilayer. We're gonna say that we have these particles that are going through the protein channel, which goes on both sides of the lipid bilayer. So they go through here which is on the outside and exit out here onto the inside. So this would be facilitated the fusion. We're using the protein channel to help us move the particles from the outside to the inside of the cell. Then finally, here we have active transport. In this one, we're gonna say protein channels or pumps use energy to move substances against a concentration gradient. We're gonna say this is highly selective and regulated different pumps for different substances. Now, some examples are our sodium potassium pumps which move sodium out and then potassiums inside the cell. So if we take a look here, energy is involved here. And that what that's what makes this active transport. It's not just simply having an integral um protein. We also have the inclusion of energy in order for our particles to go in and out of the cell, right. So just remember, we have different types of membrane membrane transport mechanisms and they deal with the transporting of materials inside and out of the cell. This has to do with nonpolar molecules, polar molecules, ions. And when it comes to active transport, we have to have the inclusion of energy
5
example
Membrane Transport Example 2
Video duration:
53s
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Video transcript
In this example question, it says how would a molecule of sic acid cross the cell membrane? Remember STAIC acid here represents a saturated fatty acid. It has the shorthand notation of 18 colon zero, meaning it has 18 carbons and zero pi bonds because of this large number of carbons. That would mean that this represents a nonpolar molecule. Remember fatty acids tend to be non po overall because of their long hydrocarbon tail because it's a nonpolar molecule that will mean that it's most likely going to cross a cell membrane by simple diffusion. Remember, simple diffusion is the transport mechanism of choice when it comes to small nonpolar molecules as well as water. So here our answer would be option A.
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Problem
Problem
How would you expect an H+ ion to move out of the cell if [H+] inside the cell is lower than extracellular fluid?
A
Simple diffusion
B
Facilitated diffusion
C
Active transport
D
None of these
7
Problem
Problem
In oxidative phosphorylation, H+ ions from the intermembrane space of mitochondria to the mitochondrial matrix, which type of membrane transport is this?
A
Simple diffusion
B
Facilitated diffusion
C
Active transport
D
None of these
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