absorption

Question 1

digestion

Answer 1

large insoluble molecules to smaller soluble molecules that are small enough to be absorbed across cell membranes into blood

Question 2

digestion of starch in mammals

Answer 2

amylase hydrolyses starch to maltose
membrane bound maltose hydrolyses maltose to glucose
hydrolysis of glycosidic bond

Question 3

Digestion of disaccharides

Answer 3

Membrane bound disaccharides hydrolyse disaccharides to 2 monosaccharides
maltase - maltose - glucose and glucose
sucrase - sucrose - fructose and glucose
lactase - lactose - galactose and glucose
hydrolysis of glycosidic bond

Question 4

lipid digestion in mammals including bile salt action

Answer 4

bile salts emulsify lipids causing them to form smaller lipid droplets
this increases SA of lipids so faster lipase activity
lipase hydrolyses lipid to monoglcyerides and fatty acids
hydrolysis of ester bond

Question 5

protein digestion

Answer 5

endopeptidases hydrolyse internal peptide bonds within polypeptides to smaller polypeptides
so more ends for exopeptidases
exopeptidase hydrolyse the terminal amino acid at end of polypeptide so a single amino acid
membrane bound dipeptidases hydrolyse peptide bond between dipeptide so 2 amino acids and the hydrolysis of peptide bon d

Question 6

why are membrane bound enzymes important in digestion

Answer 6

membrane bound enzymes located on cell membranes of epithelial cell lining ileum
they maintain a conc gradient for absorption

Question 7

pathway of absorption of digestion in mammals

Answer 7

lumen inside ileum -> cells lining ileum -> blood

Question 8

describe absorption of amino acids and monosaccharides in mammals

Answer 8

sodium ions AT from epithelial cells lining ileum to blood by na k pump
establishing a conc gradient of na (higher in lumen than epithelial cells
na enters epithelial cells down its conc gradient with glucose against its conc gradient
via a cotransporter protein
glucose moves down a conc gradient into blood via FD

Question 9

absorption of lipids by mammal

Answer 9

micelles - contain certain bile salts monoglycerides and FA
make monoglycerides and fatty acids more soluble in water
+ carry to cell lining
mono and FA absorbed into epthelial cells by diffusion
Triglycerides reformed in epithelial cells and aggregate into globules
globules coated with protiens to form chylomicrons which are then packaged into vesciles
vesicles move to cell membrane and leave via exocytosis
enter lymphatic vessel and return to blood circulation

Question 10

Use the information provided to explain the effect that glycaemic load of the
diet has on the risk of developing CHD.

Answer 10

higher gl in diet leads to more harmful lipids in blood so greater risk of atheroma
atheroma leads to blockage of coronary arteries so increased risk of blood clot in coronary artery