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10. Lipids

Peripheral Membrane Proteins


Peripheral Membrane Proteins

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in this video, we're going to talk more details about peripheral membrane proteins and so recall in our previous lesson videos, we already introduced peripheral membrane proteins, and so we already know that peripheral membrane proteins air found on the periphery or on the perimeter of the lipid bi layer. And so, if you take a look at our image down below, notice that all of these blue proteins that you see here are the peripheral membrane proteins. And so one thing to note is that the peripheral membrane proteins again are on lee on the perimeter of the membrane, and they're not integrated into the membrane like integral membrane. Proteins are, and so this purple, when you see, is an integral membrane protein. Now. Also, unlike integral membrane proteins, which are integrated and tightly associated with the membrane, peripheral membrane proteins, which are on the periphery or perimeter, are only loosely associated with the membrane, which means that it's much, much easier to remove these peripheral membrane proteins from the membrane and slight changes, like changes in Ph or changes in the ionic strength of a solution can remove these peripheral proteins from the membrane. Now, also, these peripheral membrane proteins can associate with the membrane on either side so you can find them on both the extra cellular side of the membrane. Or you could find them on the intracellular side of the membrane and these peripheral membrane proteins again. Unlike integral membrane proteins, they're going to associate with the membrane via electrostatic interactions and hydrogen bonding. And really, these air the main interactions that allow peripheral membrane proteins to associate with the membrane. And so this is different from the integral membrane proteins, because the integral membrane proteins mostly associate with the membrane through hydrophobic interactions with the other fatty acid chains, but the peripheral membrane proteins. Because they don't really interact with the fatty acid chains, they don't really form hydrophobic interactions. They form electrostatic or hydrogen bonding interactions. And so another important thing to note is that these peripheral membrane proteins can either associate directly with the membrane through interacting with the polar head. Groups of foster lipids or the peripheral membrane proteins could, uh, interact indirectly with the membrane through interacting with the exposed surfaces of integral proteins, and so notice that this peripheral membrane protein is interacting directly with the phosphor, a lipid heads that you see here forming electrostatic interactions and hydrogen bonding. However, notice that this this peripheral protein right here is not really interacting with the foster A lipid heads. Instead, it's associated with the membrane because it's interacting with the exposed surface here of this integral membrane protein. And so that's exactly what this here is pointing out. Now, the last idea I wanna leave you guys off with is this idea of an fee tropic proteins. And so this is a very specific type of peripheral membrane protein that can also be found diffused in the site us all, which is the liquid that's found on the intracellular side of the membrane. And so what you can see here is that this particular peripheral membrane protein is associated with the intracellular side of the membrane and interacting with these fossil lipids. But you'll also notice that this peripheral membrane protein has the ability to disassociate from the membrane and become dissolved or diffused in the sight of Saul, which again, is just this solution that's on the intracellular side of the membrane and so anti tropic proteins you confined both associated with the membrane. Or you can find them dissolved in the sight of Saul and really that is it for anti trophic proteins. And so this here concludes our lesson here on peripheral membrane proteins, and we'll be able to apply the concepts that we've learned in our next couple of videos, so I'll see you guys there.

Peripheral membrane proteins: 

a) Penetrate deeply into the lipid bilayer. 

b) Can only be released from membranes by disrupting membrane structure via treatment with detergents. 

c) Are non-covalently bound to membrane lipids or integral proteins. 

d) Consist of β-barrels forming a hollow cylinder that creates a pore within the membrane. 

e) Are covalently attached to carbohydrates that span the bilayer.


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: ___________.

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