BIOL 221 Lecture Notes - Lecture 8: Active Transport, Brush Border, Gastrointestinal Tract
4 Mar 2020
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Protein digestion continues in the small intestine with the action of pancreatic proteases. These enzymes trypsin, chymotrypsin and carboxypolypeptidase are secreted as inactive precursors referred to as zymogens (trypsinogen, chymotrypsinogen, and pro carboxypolypeptidase, respectively) to protect the intestinal mucosa from being digested. These enzymes hydrolyze large proteins into small peptides (usually di- or tripeptides). Brush border enzymes (aminopeptidase and dipeptidase) complete protein digestion by hydrolyzing the small peptides into individual amino acids. Amino acids are absorbed by cotransport with sodium. Proteins are rarely absorbed intact and often cause food allergies when they are. Pancreatic nucleases cleave nucleic acids into nucleotides. Nucleic acids are hydrolyzed into nucleotides by pancreatic nucleases. Brush border nucleosidases and phosphatases hydrolyze nucleotides into their components: sugar (ribose or deoxyribose), phosphate, nitrogen bases. These are then transported actively into the cells. C, b complex mostly absorbed by diffusion. Think spot: what blood disorder is associated with this? (topic 1)
