Digestion And Absorption Flashcards
Starch digestion model answer
Amylase in saliva hydrolyses starch (by breaking the glycosidic bond) to maltose
• Amylase is denatured in the stomach – no carb digestion there
• Pancreatic amylase is released and further hydrolyses any leftover starch
• Maltose is hydrolysed to α-glucose by breaking the glycosidic bond in the ileum by the enzyme maltase which is a membrane-bound enzyme
• Glucose is absorbed in co-transport
Protein digestion model answer
Hydrolysis of peptide bonds.
• Endopeptidase act in the middle of protein/polypeptide in the stomach and produces shorter polypeptides, increasing the number of ends
• Exopeptidases act at end of protein/polypeptide and in the stomach and produce dipeptides.
• Dipeptidases are membrane bound enzymes in the ileum which act on dipeptides and produce single amino acids
What do exopeptidases do?
hydrolyse peptide bonds on the ends of polypeptides in the stomach
What do endopeptidases do?
hydrolyse peptide bonds within polypeptides in the stomach
What do dipeptidases do?
they are membrane bound enzymes in the ileum which hydrolyse dipeptides into single amino acids to be absorbed by co transport into the cells
Lipid digestion model answer
Bile salts emulsify lipids into micelles to increase surface area and solubility in water
• Lipids/triglycerides are hydrolysed by lipases to form fatty acids and monoglycerides
• Micelles contain fatty acids, monoglycerides and bile salts
• They move through the ileum to the epithelium cells
Lipid absorption model answer
Micelles contain bile salts and fatty acids/monoglycerides, making them soluble in water.
• Fatty acids/monoglycerides are released to cell/lining of the ileum.
• This maintains a higher concentration of fatty acids/monoglycerides outside the cell, so they are absorbed by simple diffusion.
• Triglycerides are reformed in cells and form chylomicrons.
• The chylomicron vesicles fuse with the cell membrane and are released by exocytosis.
