digestion

Question 1

digestion of starch

Answer 1

starch -> maltose
by amylase
made in salivary glands and pancreas
acts in mouth and small intestine
hydrolyses glycosidic bonds

maltose -> alpha glucose
by maltase
disaccharidase membrane bound on epithelium of small intestine

Question 2

digestion of proteins

Answer 2

proteins -> polypeptides
by endopeptidases
hydrolyse internal peptide bonds
in stomach (acidic)

polypeptides -> dipeptides
by exopeptidases
hydrolyse terminal peptide bonds

dipeptidases -> amino acids
by dipeptidases
membrane bound on epithelium of small intestine

Question 3

digestion of lipids

Answer 3

bile salts
made in liver
stored in gall bladder

emulsify lipids into smear pieces
increases surface area for enzymes

lipase
from pancreas
works in small intestine
hydrolyses ester bonds
into fatty acids and monoglycerides

Question 4

how are the products of starch digestion absorbed?

Answer 4

glucose absorbed by co-transport

sodium ions active transported from ileum epithelial cells into blood
by sodium potassium pump
makes concentration of sodium ions
higher in lumen then epithelial cells
sodium ions diffuse down concentration gradient into epithelial cells
through co-transporter proteins
takes glucose with it

Question 5

how are the products of protein digestion absorbed?

Answer 5

amino acids absorbed by co-transport
in ileum

involves sodium ions being actively transported from ileum epithelial cells into blood
makes a concentration gradient of sodium ions
(higher in lumen of ileum than epithelial cells)
sodium ions diffuse down concentration gradient into epithelial cells through co-transporter proteins
carrying amino acids with them

Question 6

how are the products of lipid digestion absorbed?

Answer 6

monoglycerides and fatty acids arrange into micelles
micelles mean more soluble
so move products towards epithelium of small intestine
break up and release them

can diffuse across membrane (as they are lipid soluble) and non-polar

fatty acids and monoglycerides reformed into triglycerides

Question 7

micelles made of…

Answer 7

monoglycerides
phospholipids
fatty acids (phospholipids)
bile salts

Question 8

what is a chylomicron?

Answer 8

sphere of phospholipids and lipoproteins which incase triglycerides
protected from water as hydrophobic