Types of Membrane Proteins - Video Tutorials & Practice Problems

Types of Membrane Proteins

So from our last lesson video, we know that proteins are a major component of biological membranes. And so here in this video, we're going to talk about some of the types of membrane proteins. And really, we're going to focus on 2 main types of membrane-associated proteins, and notice we have them numbered down below, number 1 and number 2. And so the very first membrane protein that we're going to talk about is the integral membrane proteins. And so the integral membrane proteins, as their name implies with the integral part here, are integrated into the cell membrane. Usually, the integral membrane proteins are going to be spanning the entire phospholipid bilayer. And so if we take a look at our image down below, notice that this purple protein that you see right here that's embedded within this phospholipid bilayer, is an integral membrane protein because it's integrated into the phospholipid bilayer. And it's also spanning the entire phospholipid bilayer. Notice that it has an intracellular portion towards the inside of the cell. It also has an extracellular portion that's towards the outside of the cell, and it has this portion here that is completely integrated into the membrane. And so that's why number 1 here is going to be an integral membrane protein. Now the second type of membrane protein that we're going to talk about are the peripheral membrane proteins. And so the peripheral membrane proteins, as their name implies with the peripheral part, are proteins that are going to be found on the periphery or in other words, proteins found on the perimeter or on the outside of the cell membrane. And so if we take a look down below at this image over here, notice that this green protein that we see here is not fully integrated into the membrane. Instead, it remains on the periphery or the perimeter of the cell membrane. And so this is going to make this green protein a peripheral membrane protein. Now these membrane proteins can have all kinds of different functions. And so in our next lesson video, we'll talk about some of their functions. So I'll see you all there.

Membrane Protein Functions

In this video, we're going to talk about some of the functions of membrane proteins or what exactly do these membrane proteins actually do? Well, it turns out that membrane-associated proteins can actually perform a wide variety of functions. They can do so many different things, and we're not going to talk about every single function that membrane proteins have, but some of those functions include the following functions that we have in this table down below. Now notice over here on the left-hand side, we have this little baby rattle, and the reason for that is that hopefully this little rattle will help jog your memories of some of the membrane protein functions that we have in this table here. And the reason for that is because the first letter of each of these functions is going to spell the word rattle, and so here what we have are the letters that spell the word rattle. And so hopefully this little rattle over here will help jog your memories of some of the membrane protein functions.

Now, the first function that we have here is recognition, and so membrane proteins can be used for recognition to mark cells for identification. Very similar to how your ID in your wallet marks you for identification. Now, membrane proteins can also be used for anchorage, where the cell's cytoskeleton and the extracellular matrix can be anchored together. And so here what we have is a little image of an anchor to remind you of that function.

Now, membrane proteins can also be important for transduction, essentially allowing signals, acting as receptors for signaling molecules. And so here what we have is a little receptor showing you that they can be used to detect signals. Now, membrane proteins can also be really, really important for transport. Moving forward in our course, we're going to talk a lot more about transport across membranes. And so, the transport here is just molecular transport across a membrane, very similar to how cars can be used for transportation, membrane proteins can also be used for transportation.

Now, membrane proteins are also really important for linkage, essentially connecting two cells together via a protein linkage, just like these two little paper clips are connected together, in that fashion. And then last but not least, proteins in the membrane can be used as enzymes, and so many types of enzymatic processes can be catalyzed by membrane proteins. And so here what we have is a little enzymatic reaction, and we'll get to talk more about enzymes a little bit later in our course. But for now, this here concludes our brief introduction to some of the membrane protein functions, and we'll be able to get some practice applying these concepts as we move forward throughout our course. So I'll see you guys in our next video.

Which of the following is NOT a function of membrane proteins?

• A. Transducing signals from the environment into the cell.
• B. Synthesizing proteins.
• C. Anchoring the cell cytoskeleton and extracellular matrix.
• D. Marking cells for recognition.