Starch Digestion And Absorption Flashcards
Process of starch digestion
1) Food enters mouth and mechanically digested by teeth, then mixed with saliva
2) Salivary amylase starts to hydrolyse glycosidic bonds in starch producing maltose (chemical digestion)
3) In the stomach, the salivary amylase is denatured due to acidic pH
4) In the small intestines, pancreatic amylase continues to hydrolyse the starch into maltose
5) Maltose is then hydrolysed into glucose by the membrane-bound maltase, which is embedded into the cell surface membrane of epithelial cells that line the ileum
6) Glucose is then absorbed in the ileum
Enzymes involved in starch digestion
Amylase -> Synthesised and secreted from salivary glands and pancreas = Starch to Maltose
Maltase -> Membrane-bound of epithelial cell of ileum = Maltose to glucose
Process of glucose absorption
1) Na+ (sodium ions) are actively transported out of epithelial cells into the blood - by the sodium-potassium pump which requires ATP
2) This creates a concentration gradient of Na+ between lumen of ileum and the epithelial cell
3) Na+ and glucose enter by facilitated diffusion using a complementary co-transport protein that has two binding sites specific to each molecule
4) Na+ diffuses into the cell down a concentration gradient
Glucose diffuses into the cell against a concentration gradient
5) Glucose moves into the blood by facilitated diffusion via a carrier protein that has one binding site
Adaptations of ileum epithelial cell
-1 cell thin to provide a short diffusion pathway
-Extensions to increase surface area as well as more membrane for enzymes + proteins for absorption
-Main mitochondria to produce large amounts of ATP for active transport by sodium potassium pump
