in this video, we're going to talk even Mawr details about integral membrane proteins, and so recall that we already introduced integral membrane proteins in our previous lesson videos. And so we already know that integral membrane proteins are integrated into the membrane, as we can see down below. And so these are membrane embedded proteins. Now, because integral membrane proteins are integrated into the membrane, they're pretty firmly anchored to the membrane, which means that they are tightly associated with the membrane. And this is because they form lots and lots and lots of hydrophobic interactions with all of the fatty acid changed that surround them in the face of a lipid bi layer. And so these integral membrane proteins are so tightly associated with the membrane that if we wanted to isolate an integral membrane protein from the membrane, we would first have to disrupt the structure of the membrane using a detergent. And then, after we disrupt the structure of the membrane, we could then isolate the integral membrane protein. And so that just goes to show that these integral membrane proteins are really tightly associated with the membrane. Now, the hydrophobic environment within the membranes actually stabilize alfa helix structures. And so the Alfa Helix is actually the most prevalent secondary structure in integral membrane proteins. And so whenever you see an integral membrane protein, the likelihood is that it's probably going to contain an Alfa helix structure. And so what you'll notice is looking down below it are image over here on the left notice. We're showing you to integral membrane proteins. Glick, Oh, foreign over here on the left and reduction over here on the right and notice that they both form lots and lots of alfa helix structures within the hydrophobic environment, which is going to again stabilized the Alfa helix structure. Now, integral membrane proteins contain at least one trans membrane spanning domain. And so the trans membrane spanning domain again generally includes an Alfa helix structure. And so notice that Glencoe Foreign over here on the left has one Alfa helix, and so therefore, it has one trans membrane spanning domain. But then notice Over here on the right hand side, Redon person actually has a total of seven. Alfa Healy sees that we're labeling here, and so because it has these seven Alfa he'll seize. It also has seven trans membrane spanning domains. Now, if there are multiple trans membrane spanning domains there typically connected by loops at the membrane surface. And so notice that the Alfa Healy sees here are connected by these loops that we see at the surface of the membrane. And so that's another important idea to note. Now, over here on the right hand side, we're reminding you guys of how proteins tend to fold, depending on the environment that the proteins are in. And so in polar acquis environments, proteins will fold in such a way where the polar amino acids are on the perimeter so that they can interact with the polar acquis environment, and the non polar amino acids would fold into the interior of their protein because they are hydrophobic. However, what's important to note is that in the opposite environment, in a hydrophobic environment within a membrane like this one over here on the right hand side, notice that the protein folds in the opposite way. Notice that on the perimeter of the protein this time, the non polar amino acids are gonna be on the perimeter, and the polar amino acids are going to be on the interior and again. This is going to be occurring on the inside of the membrane in that hydrophobic environment. And so that's an important idea to keep in mind about protein folding. And so this year concludes our introduction to integral membrane proteins, and in our next lesson video, we'll be able to introduce a very specific integral membrane protein, so I'll see you guys there.
Integral Membrane Proteins
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So in our last lesson video, we said that the Alfa Helix is the most common secondary structure in integral membrane proteins. But in this video, we're going to talk about an exception, which is in the integral membrane proteins called por ins, which have beta barrel motifs. And so, as we just mentioned, por ins are just a class of integral membrane proteins that contain a beta barrel motif. And so recall from way back in our previous lesson videos that ah motif is just a pattern or a combination of secondary protein structures. And so, as the name implies, porn's function as pores or channels to allow specific molecules to cross the membrane. Now this beta barrel motif is really just a combination of anti parallel beta sheets that come together to form a hollow cylinder. And this hollow cylinder has a hydro filic interior and a hydro phobic exterior, and this specific pattern allows the passage of specific polar molecules to cross the membrane. And so what's important to note is that these porn's are commonly found in bacterial cell membranes as well as in the membranes of mitochondria and chloroplasts. And so really, this is not a surprise since we know the end of symbiotic theory suggests that mitochondria and chloroplasts used to be their own bacteria. And so again, not really a surprise that the bacteria, mitochondria and chloroplasts all share this poor int integral membrane protein in common. And so, if we take a look at our image down below notice on the far left, we're showing you the beta barrel motif, which is again just a combination of anti parallel beta sheets that form this hollow cylinder. And again, the hollow cylinder has a hydro filic interior and a hydrophobic exterior. And so when it's embedded in the membrane, as we see here, the hydrophobic exterior is able to interact with the hydrophobic membrane. And then, of course, the hydro filic interior allows the passage of specific polar molecules to cross the membrane. And again, over here on the far right, we're just reminding you that these poor ins are commonly found in the membranes of both mitochondria and chloroplasts as well as in bacteria. But of course the mitochondria is going to be more relevant to us. And so this here concludes our introduction to poor ins and beta barrel motifs and again. This is an exception to integral membrane proteins, and we'll be able to get some practice applying the concepts that we've learned in our next couple of videos, so I'll see you guys there.
Which of the following statements about integral proteins is NOT correct?
a) They are firmly associated with the membrane.
b) They contain hydrophobic regions that interact with hydrophobic lipid tails.
c) They can be easily extracted/separated from lipid membranes by just a relatively small change in the pH.
d) They commonly contain α-helices or multi-stranded β-barrels.
They are firmly associated with the membrane.
They contain hydrophobic regions that interact with hydrophobic lipid tails.
They can be easily extracted/separated from lipid membranes by just a relatively small change in the pH.
They commonly contain α-helices or multi-stranded β-barrels.
Integral membrane proteins are proteins that:
a) Loosely associate with the membrane.
b) Can be released from the membrane by slightly changing the pH.
c) Can be released from the membrane by slightly changing the ionic strength of the solution.
d) Penetrate or span the membrane.
Loosely associate with the membrane.
Can be released from the membrane by slightly changing the pH.
Can be released from the membrane by slightly changing the ionic strength of the solution.
Penetrate or span the membrane.
In the hydrophobic environment of a membrane, the α-helix of a protein folds such that the outer surfaces contain mostly _________________ amino acids, while _________________ amino acids are mostly buried on the inside.