Physiology 3140A Lecture Notes - Lecture 6: Insulin Receptor Substrate, Royal Aircraft Factory F.E.2, Golgi Apparatus
28 Dec 2017
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Diffusion: down concentration gradient, passive transport, good for small, hydrophobic molecules, hydrophilic molecules need channels they cannot get across alone. Facilitated diffusion: down concentration gradient (passive, uses protein carriers (protein-mediated, no energy required (atp, specific for a certain molecule, limited capacity can be saturated, can be competitively inhibited. Secondary active transport: similar to facilitated diffusion except: one molecule moves down its concentration gradient (active) Active transport: requires atp, specific, limited capacity can be saturated, can be competitively inhibited. Nutrient extraction from the lumen of the small intestine requires specific transporters in the absorptive epithelia. Gastrointestinal tract is lined with epithelium and it can vary. Duodenum is considered a leaky epithelium: absorbs majority of nutrients. Large intestine is tight epithelium: water absorption is transcellular, glucose and other nutrients need to go through the cells because they cannot move between the cells. Small intestine is similar to reabsorption of nutrients/ions in the kidney tubules.
