quick bio question
Started by TypeSH07
protein digestion begins in the stomach with HCl secreted from the parietal cells and pepsinogen secreted by the chief cells. Pepsinogen is inactive until it mixes with HCl and then becomes the active form pepsin. pepsins job is to break down proteins into peptides.
EK is correct for the digesetion part. Both are correct as far as absorption....that begins in the small intestein, which is why they have villi to increase the surface area and absorb as much as possible.
You must understand though that MANY drugs (the weak acids) get absorbed through the stomach...Drugs that are weak bases will get absorbed in the intestine...
I think you may have read something wrong. I am also taking Princeton, and my book explicitly states that pepsin (which is activated from pepsinogen by HCl) breaks protein polypeptides into fragments. Proteins get furthur broken down in the small intestine by pancreatic peptidase and pancreatic zymogens (polypeptides = dipeptides & tripeptides). Afterwards brush border enzymes break down the dipeptides into monomers (amino acid). Amino acids are then transported into the intestinal epithelial cells by Na+/AA symport. Then uniporter transports AA into the interstitium. AAs eventually end up in the liver. Hope this helps.
