Types of Membrane Proteins - Video Tutorials & Practice Problems
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Types of Membrane Proteins
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So from our last lesson video we already know that proteins are a critical component of biological membranes and so in this video, we're going to focus on some of the different types of membrane proteins. And so really there are two main types of membrane associated proteins that you should be familiar with and notice down below we're numbering them number 1 and number 2. And of course, the numbers up above in the text correspond with the numbers that you see down below in the image. And so the first type of membrane protein that you should be familiar with are the integral membrane proteins. And so these integral membrane proteins as their name implies, are going to be integrated or embedded within the cell membrane and usually they will be spanning the entire phospholipid bilayer. And so if we take a look at our image down below notice we're showing you a biological membrane right here and notice that towards the top is the outside of the cell and of course towards the bottom is the inside of the cell. And what you'll notice is we've got this purple protein here that is completely integrated and is spanning the entire biological membrane. And so notice that it has an intracellular portion of the protein that's facing towards the inside of the cell, It has an extracellular portion of the protein that's, towards the outside of the cell and then of course it has an integrated region and so this is why we call this an integral membrane protein. Now the other type of membrane protein are the peripheral membrane proteins. And the peripheral membrane proteins, as their name are going to be proteins that are found on the periphery or in other words, proteins found on the perimeter of the biological membrane. And so they will not span the membrane like the integral membrane proteins do. And so if we take a look at our image down below, notice right over here we're showing you an example of a peripheral membrane protein. And so notice that this protein is only going to have an extracellular portion on the outside of the cell. It is not integrated or embedded in the phospholipid bilayer and it does not have an intracellular portion. And so it is on the perimeter, it is a peripheral membrane protein. Now peripheral membrane proteins can either be on the extracellular side or the outside of the cell, but you could also potentially have another peripheral membrane protein on the inside or the intracellular side of the biological membrane. So that's important to keep in mind. Now these, membrane proteins whether they are integral or whether they are peripheral can have a wide variety of different functions and so moving forward in our next video, we'll get to talk more about the functions of these membrane proteins. So I'll see you all in our next video.
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Membrane Protein Functions
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In this video we're going to talk about some of the different types of functions that membrane proteins can have or what do these membrane proteins actually do. And so membrane associated proteins can actually perform a wide variety of functions. They can do so many different types of things and so we're not going to cover every single function that membrane proteins can have but some of those functions are included in the following table that you see down below. And so notice on the left hand side over here we're showing you this little baby rattle and that's because hopefully by remembering rattle it'll help jog your memory of some of the membrane protein functions that we have in this table. And the reason for that is because the first letter of each of these membrane protein functions spells out the word rattle as you can see right here. And so again that's why we have this rattle here just to help jog your memories. And so the very first membrane protein function that we have listed here is recognition and this is because membrane proteins can actually mark a cell for identification. And so just like a driver's license can mark you for identification, membrane proteins can mark cells for identification and help cells distinguish one cell from another cell. Now the next protein function that we have here is anchorage and so some membrane proteins can anchor the cell cytoskeleton to the extracellular matrix or the ECM. And so cell cytoskeleton and ECM anchoring is a critical function in some scenarios and so over here on the right we're showing you a little image of an anchor to remind you of that function. Now the 3rd function that we have here is transduction and so this is when some membrane proteins serve as receptors for signaling molecules allowing for bio signaling to take place. And so transduction basically allows a signal on the outside of the cell to affect the metabolism of the cell on the inside. And so over here what we're showing you is a little receptor just to remind you of that function. Now the 4th function that we have here is transport and so some membrane proteins can help with molecular transport across the membrane which is a function that we'll get to talk more about moving forward in our course. And so just like vehicles like cars can be used to transport objects, membrane proteins in some cases can also be used to transport objects across the membrane. Now the 4th function that we have is linkage and so some membrane proteins can connect to cells via a protein linkage. And so we did talk about some cell junctions in some of our previous lesson videos and so over here, just like these two pieces of a chain are being linked together, some membrane proteins can link together to neighboring cells. And then last but not least, the final function that we have listed here is enzymes. And so some membrane proteins can serve as enzymes to speed up chemical reactions and so many types of enzymatic processes can rely on these membrane proteins to serve as enzymes and so over here what we're showing you is just a little basic, enzymatic reaction, just to remind you of that function. And so once again, by remembering the word rattle hopefully this will help you jog your memory of some of these membrane protein functions that are in this table. And so this concludes our brief lesson on membrane protein functions and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
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Problem
Problem
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.