Label each of the following as a characteristic of (A) Integra...

Question

Label each of the following as a characteristic of (A) Integral and/or (B) Peripheral Membrane Proteins:

a) Could function on either side of the membrane: ___________.

b) Can act as a tunnel through the cell membrane: ___________.

c) Attaches only at the surface of a cell's membrane: ___________.

d) Extends through all or part of the membrane: ___________.

e) Loosely associated with the membrane: ___________.

f) Can act as amphitropic proteins: ___________.

Accepted Answer

So this practice problem wants us to label each of the following down below as either a characteristic of a, integral membrane proteins, and or B, peripheral membrane proteins. And so what can be helpful here is for us to draw a sketch of integral and peripheral membrane proteins. And so when we do that, we could get something that looks something like this, where you can see we have our phospholipid bilayer right here. And then, of course, the integral membrane protein is this one right here, spanning the entire membrane. And then the peripheral membrane protein is down over here on the perimeter. Now looking at part a, it says could function on either side of the membrane, and of course, this is referring to either functioning on the extracellular side of the membrane or functioning on the intracellular side of the membrane. Now, it turns out that both, a, integral membrane proteins, and, b, peripheral membrane proteins can function on either side of the membrane. And this is because integral membrane proteins, they can have an extracellular region like this one that could have function on the outside of the cell and the integral membrane protein could also have an intracellular region that could have function on the inside of the cell. And so integral membrane proteins can function on either side And same goes for peripheral membrane proteins because they could either be associated with the intracellular side, but they could very well easily be on the extracellular side as well. And so, both, A and B, could function on either side of the membrane. Now, moving on to part B, it says, can act as a tunnel through the cell's membrane. Now, of course, because peripheral membrane proteins are only on the perimeter or the periphery, they can't really act as a tunnel to allow things to cross the membrane. Instead, the integral membrane proteins are perfect for this because they, span the membrane and they can create a tunnel allowing molecules to travel through the tunnel and get through the membrane. And so, part b here is only going to apply to a integral membrane proteins only. Now part c says, attaches only at the surface of a cell's membrane. And of course, we know that this is going to apply to the peripheral membrane proteins. Those are the ones that are, only attached to the surface. And so we can go ahead and put b here for peripheral membrane proteins. Now d says extends through all extends through all or part of the membrane. And, of course, we can visually see here that this only applies to the integral membrane protein, a here. Now, e says, loosely associated with the membrane. Now, recall from our previous lesson videos that integral membrane proteins because they are integrated in the membrane, they form lots and lots of hydrophobic interactions with all of these fatty acid side chains that are here. And this allows them to be firmly anchored or tightly associated with the membrane. And so it's really the peripheral membrane proteins that are on the, parameter that are going to be the ones that are loosely associated with the membrane. And so this only applies to b, the peripheral membrane proteins. And then of course, last but not least, f says can act as amphitropic proteins. Now recall from our last lesson video that amphitropic proteins are proteins that can both be associated with the membrane, but also reversibly bind to the membrane and act as proteins that are dissolved in the cytosol. And so, of course, this is only going to apply to peripheral membrane proteins. The ability to associate with the membrane and dissociate with the membrane can only, apply to something that is loosely associated with the membrane. Integral membrane proteins would have a really hard time, separating from the membrane and acting as a dissolved, cytosolic protein. And so again, this is only going to apply to peripheral membrane proteins. And so this here concludes our practice problem and I'll see you guys in our next video.

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