Where are proteins located in cell membranes?

Question

Accepted Answer

Hello, everyone. Our next problem says, determine the location of integral and peripheral proteins in the cell membrane. And we've got four answer choices we can evaluate. But this one just to orient ourselves, it's pretty easy to remember which is which just do the meanings of the word. So if we think of in integral versus peripheral peripheral, on the side, not as important. Well, in this case, not as important, isn't the meaning we want but on the side, peripheral being at just attached um to the exterior surface or the interior surface. Whereas integral we think of like just really important or you know, a part of and integral membrane proteins are within the membrane. So put within membrane while peripheral are attached to the membrane. So with those basics in mind, let's evaluate our answer choices. Choice A says the integral proteins are loosely attached to the exterior or an interior surface of the exterior or interior surfaces of the membrane. While the peripheral proteins are embedded within a lipid bilayer and can span across the membrane. Well, this is obviously flipped. It's the peripheral proteins that are loosely attached on the surface. Whereas the integral or integral proteins are the ones that are embedded within that lipid bilayer and can span completely across the membrane. Should I say incorrect to pieces? The integral proteins are permanently attached to the exterior or interior surfaces of the membrane. While the peripheral proteins are spread within the lipid bilayer and can span across the membrane. This one is also incorrect but it brings up another class of type of membrane, a type of protein attached to the cell membrane. And that would be a protein that is permanently attached to the exterior interior surface of the membrane, which is not an integral protein, integral means within that membrane, but a what's called a lipid anchored protein. So again, the name can help you here, it's anchored, it's permanently attached, not just loosely attached to the lipids of that lipid bilayer. And then our second part is incorrect as well. It is not the peripheral proteins that are spread within the lipid bilayer and can span the membrane. That's the integral proteins. So choice B also incorrect. Now on to choice C which says the integral proteins are spread within the lipid bilayer and can span across the membrane. All the peripheral proteins are permanently attached to the exterior or interior surfaces of the membrane. Well, part one here is it correct? But again, this part two is not peripheral proteins but the lipid anchored proteins. So it's the second half that makes choice c incorrect. So now we just got one left. So we know choice D must be our answer. But let's look through it. And it says the integral proteins are embedded within a lipid bilayer and can span across the membrane while the peripheral proteins are loosely attached to the exterior or interior surfaces of the membrane. So here we have a statement where both parts are correct about the location of both the integral and peripheral proteins in the cell membrane. So choice D here is our answer. See you in the next problem.

Where are proteins located in cell membranes?

Verified video answer for a similar problem:

Key Concepts

Cell Membrane Structure

Integral and Peripheral Proteins

Membrane Fluidity