Biology AQA 3.1.3 Absorption

Question	Answer
Diffusion	The passive net movement of molecules from a region of high concentration to low
Active transport	The net movement of molecules with the use of ATP (energy) to move molecules from a region of low concentration to high
Carrier protein	An intrinsic protein across a plasma membrane stimulated by ATP
Vili and microvilli are used in the absorption of carbohydrates in the small intestine	They have: A large surface area good blood supply moist lining close diffusion pathway lots of capillaries
Diffusion in the Villi.	1. Starch is hydrolysed to make glucose so diffusion can occur 2. glucose is a monosaccharide so can be absorbed 3.in the blood there is a low concentration of glucose 4. diffusion occurs across the epithelial in the blood
Image: glucose-transport01 (image/jpg)	1. NA+ actively transports out of epithelial cell into the blood by na+K+ pump (carrier protein) 2. due to NA+ entering the blood there is now a higher concentration in the lumen compared to epithelial 3. Na+ diffuses into the epithelial down the concentration gradient through a protein carrier 4. Na+ has to couple up with glucose to diffuse in, so glucose also enters the cell 5. glucose goes in the blood by facilitated diffusion

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	Created by evie.daines about 10 years ago