digestion

Question 1

describe the digestion of starch

Answer 1

salivary glands make salivary amylase. in the mouth amylase hydrolyses starch to maltose. food chewed
pancreas makes pancreatic amylase. small intestine pancreatic amylase further hydrolyses starch to maltose. epithelial lining of small intestine also makes maltase which hydrolyses maltase to alpha glucose
glucose absorbed by villi on small intestine

Question 2

how is glucose absorbed

Answer 2

co transport of glucose with sodium. sodium ions actively transported to blood from epithelial cells by Na/K pump. forms diffusion gradient for sodium to enter epithelial cell from intestinal lumen. sodium ions couple with glucose. glucose enters the epithelial cell by facilitated diffusion with a sodium ion. glucose enters blood down conc gradient through protein channel by fac diffusion.

Question 3

describe the digestion of proteins

Answer 3

happens through the hydrolysis of peptide bonds
endopeptidases hydrolyse internal peptide bonds turn polypeptides into smaller peptide chains exposes more ends for exopeptidases
exopeptidases remove terminal amino acids
dipeptidases break peptide bonds between dipeptides and form amino acids

Question 4

describe the digestion of lipids

Answer 4

lipids emulsified into smaller droplets by bile salts
droplets increase surface area for lipase action so its faster.
lipase hydrolyses triglycerides/lipids into micelles which carry fatty acids and glycerol through the membrane to intestinal epithelium by diffusion

Question 5

describe the absorption of lipids

Answer 5

Golgi apparatus modifies and processed the triglycerides
combines triglycerides with proteins to form chylomicrons
packaged for release through exocytosis or forms vesicles
chylomicrons enter lymphatic system eventually draining into the circulatory system
triglycerides are hydrolysed by an enzyme in the endothelial layer of the capillaries
fatty acids can then diffuse into cells