HTHSCI 1LL3 Lecture Notes - Lecture 16: Red Blood Cell, Extracellular Fluid, Tabloid Journalism
17 Mar 2017
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Document Summary
Hcl in the stomach allows the autocatalytic conversion to pepsin. Pancreatic enzymes: once the food leaves the stomach, the pancreas releases enzymes as well as bicarbonate ions to neutralize the acidic chyme so that the enzymes can function. The pancreatic proteases are all released as zymogens, so that they do not digest each other; trypsinogen is cleaved to trypsin by enteropeptidase secreted by the brush border cells. Trypsin, in turn, cleaves the other zymogens to activate them in the intestine, where they break proteins down to di- and tri-peptides. Amino acid absorption: amino acids are transported similar to glucose in the digestive cells, absorption is by secondary active transport with sodium ions. If essential amino acids are not absorbed from the diet (or obtained from normal protein breakdown), muscle protein must be broken down to provide them. Amino acid metabolism: amino acid metabolism is more complicated than lipids or carbohydrates because amino acids contain nitrogen.
