Digestion of Proteins (Nursing)

by Jasmine Clark

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    00:01 Now let's look at the digestion of proteins.

    00:06 Note, the source of proteins is not only dietary but also includes digestive enzymes as well as proteins from the breakdown of mucosal cells.

    00:18 Proteins are going to be broken into large polypeptides, small polypeptides, and small peptides.

    00:27 And finally, into their monomeric unit of amino acids with some dipeptides and tripeptides as well.

    00:36 Digestion of proteins begins in the stomach when pepsinogen is converted to pepsin at a very low pH of about 1.5 to 2.5.

    00:48 It becomes inactive when it hits the high pH of the duodenum.

    00:56 Pancreatic protease has trypsin and chymotrypsin are then going to cleave the protein into smaller peptides while carboxy peptidase is going to take off one of the amino acids at a time from the ends of these polypeptides.

    01:15 Brush border enzymes also known as amino peptidases, carboxypeptidases and dipeptidases are going to break these polypeptides down into smaller units and eventually into amino acids.

    01:32 It is the amino acids that will then be co-transported across the apical membrane of our absorptive epithelial cells via secondary active transport with either sodium ions or H+ ions.

    01:48 Then after crossing through the cell, the amino acids will exit across the basolateral membrane by way of facilitated diffusion.

    02:00 So to recap these steps using a diagram.

    02:03 Recall that the breakdown of protein actually starts in the stomach, but once it leaves the stomach it's going to be further broken down through pancreatic proteases.

    02:17 Further at the brush border.

    02:19 There are going to be brush border enzymes that are going to break these now polypeptides or oligopeptides down into amino acids.

    02:29 These amino acids will then be transported across the apical membrane by way of active transport with either sodium or H+ ions.

    02:39 It will then travel through the cell and exit through the basolateral membrane into the bloodstream into hepatic portal circulation.

    02:50 So to summarize the digestion of proteins.

    02:54 1. protein digestion is going to begin in the stomach where the acidic environment is going to activate the protease pepsin.

    03:04 Once in the small intestine pancreatic enzymes, trypsin, chymotrypsin and carboxypeptidase as well as the brush border enzymes will then break down these proteins into amino acids.

    03:19 The amino acids are then absorbed into the blood and transported to the liver by way of the hepatic portal vein.

    About the Lecture

    The lecture Digestion of Proteins (Nursing) by Jasmine Clark is from the course Gastrointestinal System – Physiology (Nursing).

    Included Quiz Questions

    1. Pancreatic protease
    2. Pancreatic amylase
    3. Dextrinase
    4. Pancreatic nuclease
    1. Trypsin
    2. Chymotrypsin
    3. Carboxypeptidase
    4. Tripeptidase
    5. Dipeptidase

    Author of lecture Digestion of Proteins (Nursing)

     Jasmine Clark

    Jasmine Clark

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