Digestion Flashcards
How is starch digested?
Salivary amylase and pancreatic amylase in the small intestine break down the starch into maltose by hydrolyzing alternate glycosidic bonds.
Maltese on the lining of the small intestine breaks down maltose into glucose.
How is sucrose digested?
Sucrose on the lining of the small intestine breaks down into glucose and fructose.
How is lactose digested?
Lactase on the lining of the small intestine breaks it down into glucose and galactose.
What is lactose intolerance?
When someone doesn’t have the lactase enzyme
Symptoms of lactose intolerance?
Diarrhea - undigested lactose lowers the water potential of the lumen of the small intestine so water enters the lumen by osmosis.
How is glucose transported in the ileum?
- sodium ions are actively transported from the cells into the blood.
- this lowers the concentration of sodium in the cell.
- this makes sodium ions diffuse in via co-Transport proteins with the glucose
How are lipids digested?
- bile salts are produced by the liver and emulsify the lipids, which form tiny droplets called micelles which increase the surface area of the lipids.
- Then lipase breaks down the micelles into fatty acids and glycerol
How are proteins digested?
Endopeptidases - hydrolyze peptide bonds within the molecule
Exopeptidases- hydrolyze peptide bonds on the ends of molecules.
Adaptations of the small intestine?
- Villi are folded to increase surface area
- microvilli increase the surface area even more
- walls of the small intestine are thin - short diffusion distance
- rich blood supply (maintains gradient)
How are triglycerides absorbed?
Monoglycerides and fatty acids are small and non polar so can diffuse across the membrane.
- inside the cell they are recombined into triglycerides by the endoplasmic reticulum.
- triglycerides associate with cholesterol and lipoproteins and form chylomicrons (in golgi)
- chylomicrons move out by exocytosis
