Digestion Flashcards
digestion
the mechanical and chemical break down of food so it can be absorbed into the blood
mechanical digestion
breaking down large food by grinding and churning to increase SA available for chemical digestion
chemical digestion
enzymes hydrolyse covalent bonds to break down large molecules into smaller soluble molecules that can be absorbed into te blood
two types of chemical digestion
intracellular and extracellular
intracellular digestion
occurs in epithelial cells of ileum
extracellular digestion
enzymes are secreted out of cells ito the gut lumen
4 examples of extracellular digestion organs and glands
- salivary glands –> mouth
- gastric glands –> stomach
- pancreas –> duodenum
- liver –> duodenum (bile)
2 enzymes involved in intracellular digestion
disaccharidases and dipeptidases
what is the benefit of requiring multiple enzymes to fully digest a food type
the action of the fist enzyme icreases the SA available for the second enzyme so increases rate of digestions
why do different regions ofthe gut have different pHs?
enzymes have different optimum pHs
3 roles of mucus
- important in maintaining correct pH of particular regions of the gut –> neutralise stomach acid in duodenum
- provides lubrication for food to move along gut
- protects gut lining from erosion (acid atack)
what, how, where
2 steps of carbohydrate digestion
- starch is broken down into maltose by salivary and pancreatic amylase in the stomach and duodenum
- maltose is broken down into glucose by maltase in the epithelial cells of the ileum
2 disaccharidases
sucrase and lactase
what, how, where
3 steps of protein digestion
- proteins are broken down into polypeptide chains by endopeptidases (pepsin) in the stomach
- polypeptide chains broken down into shorter polypeptide chains by endopeptidases (trypsin) in the duodenum
- shorter polypeptide chains are proken down into dipeptides and amino acids by exopeptidases in the duodenum
- dipeptides are broken down into amino acids by dipeptidases (exopeptidases) inthe epithelial cells lineing the ileum
peptidases
hydrolyse peptide bonds in a polypeptide chain
endopeptidases
hydrolyse inner peptide bonds in a polypeptide chain
exopeptidases
hydrolyse end (terminal) peptide bonds in a polypeptide
3 types of exopeptidases
- aminopeptidases = N-terminal (left end)
- carboxypeptidases = C-terminal (right end)
- dipeptidases = dipeptides
2 steps of lipid digestion
- mechanical brekadown of lipid droplets into micelles by bile salts in the duodenum
- chemical digestion of micelles into monoglycerides and fatty acids by lipase in the duodenum
what is the role of bile salts in digestion of lipids?
emulsify lipid droplets to increase SA available for action of lipase