Both α-keratin and tropocollagen have helical secondary structure. How do these molecules differ in (a) amino acid composition and (b) three-dimensional structure?

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Accepted Answer

Hi, everybody. Here's our next question. True or false. Alpha keratin and troppo collagen have the same secondary and tertiary structure and only mainly differ in their amino acid composition. Well, to answer this question, we need to think about the characteristics of alpha keratin and tropical collagen. So I'm going to make two columns here. First of all, both of these are forms of connective tissue or makeup, connective tissue. I should say in the body. Alpha Carin is found in things like skin hair, nails, claws, things of that nature. It's a fibrous structural protein. Tropical collagen is also fibrous. It's the basic structural unit of collagen and it's the main structural protein of the extracellular matrix. So they're both fibrous proteins. But when we think about the amino acid makeup of these proteins, they are very different. So for keratin, the most abundant amino acids, I'll put A as are alanine A L A lucine L eu arginine A RG and cystine cys in triple collagen. On the other hand, the most abundant amino acids are prolene or pr O and glycine or gly. So you can see they do definitely have different amino acid sequences since they have totally different most abundant amino acids. So different primary structures. So that part of our statement are true, they differ, you know, acid composition. But our statement also says that they have the same secondary and tertiary structure. So this would be their primary structure. We talked about what about their secondary structure. So how the atoms of the protein backbone bond together to shape those spaces shape those spatial arrangements determined by the backbone of the protein. And in this case, it is similar, both alpha keratin and tre collagen have primarily alpha helices, determining their secondary structure. So that is the same for both of those. So now let's go to the level of tertiary structure, tertiary, tertiary. We're still talking about that 3d arrangement of the protein often called folding. So how it's arranged in space. But now we've moved on to interactions between the side chains. So whether it's covalent bonding, hydrogen bonding dile interactions interactions between side chains, whereas in secondary, we focus on interactions between the backbone atoms. And in the case of alpha Katin, there's alpha helices, you have two alpha helices that twist together in places in an arrangement called the coiled coil arrangement. Whereas in tropical collagen, you have three alpha helices that wrap around together in what's called a triple helix. So while they have the same secondary structure and having those alpha helices, they have different tertiary structures. So when we look back at our answer choices, it says that they have the same secondary and tertiary structure. So this would be incorrect tertiary structure since they have different tertiary structures, then it says and only mainly differ in the amino acid composition. That part is true. But since the description of the tertiary structure is false, the overall statement is false. And that is our answer. The statement. Alpha keratin and tropical collagen have the same secondary and tertiary structure and only mainly defer their amino acid composition is false. See you in the next video.

Both α-keratin and tropocollagen have helical secondary structure. How do these molecules differ in (a) amino acid composition and (b) three-dimensional structure?

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Key Concepts

α-Keratin

Tropocollagen

Three-Dimensional Structure