Hey, everyone. In this video, we're going to take a look at the digestion of proteins. Now here we're going to say that the main purpose of protein digestion is to produce amino acids for the synthesis of new proteins. And, we're going to say that digestion begins in the stomach, but final hydrolysis takes place inside the small intestine. Now, here we're going to segment our protein digestion in points a, b, c, and d. If we take a look here, in point a, we're going to say after mechanical digestion in the mouth, food enters the stomach. And once there, the stomach acid denatures our proteins. Here, we're going to say pepsin breaks large proteins into polypeptides. If we take a look here at our image, we have our protein source as this piece of meat, the steak. Here we're going to say point a is where we have denaturation and partial hydrolysis of that protein. We go to point b where we're dealing with proteases in the small intestine. Here, we're talking about trypsin, chymotrypsin, and other types of proteins found within the small intestine. They hydrolyze our proteins to amino acids. So here we have the denatured proteins and polypeptides. We go into point b where we have the enzymes in our small intestines. Here, we have now free amino acids. We're going to say the amino acids are directly absorbed into the bloodstream through your intestinal cells. So here are free amino acids, they're being absorbed through the intestinal cells, so this is part c, and they're going to be delivered to cells through the bloodstream. So this would be our part d here. So when we're looking at protein digestion, keep in mind these different parts, parts a, b, c, and d.
25. Protein and Amino Acid Metabolism
Digestion of Proteins
25. Protein and Amino Acid Metabolism
Digestion of Proteins - Video Tutorials & Practice Problems
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concept
Digestion of Proteins Concept 1
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example
Digestion of Proteins Example 1
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Which of the following statements is incorrect about the digestion of proteins?
- A. Denaturation in the stomach makes the peptide bonds accessible to proteases. That's true; remember that we're going to have the denaturation of our protein within the stomach. This has to occur so that later on the proteases can start to hydrolyze those proteins into amino acids. So, this is true.
- B. Pepsin in the stomach breaks large proteins into smaller polypeptides. Yes, that is true. Pepsin is going to be the enzyme that we find within our stomach, and it's going to break down our larger proteins into polypeptides.
- C. Proteases in the small intestines hydrolyze proteins and polypeptides into free amino acids. That is also true.
- D. Here, protein digestion begins in the mouth by enzymes in the saliva. Remember, your saliva doesn't have enzymes that are going to help with the breaking down of our macromolecules. So this part is false. So, out of all the options, the answer has to be option D. Yes, mechanical digestion can begin in the mouth, but saliva doesn't have the necessary enzymes to start breaking down and denaturing our proteins. That's going to happen later on within the stomach.
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Problem
ProblemWhich of the following statements is correct about food digestion?
A
Lipids are completely hydrolyzed inside the stomach through acidic hydrolysis.
B
Unlike lipids, monosaccharides and amino acids are directly absorbed into the bloodstream through intestinal cells.
C
Similar to proteins, large polysaccharide chains are also denatured in the stomach.
D
Carbohydrates and amino acids are digested to produce energy while lipids enter anabolic pathways.
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