Digestion

Question 1

Protein

Answer 1

Hydrolysis of peptide bonds .
Endopeptidases break polypeptides from the middle of the chain into smaller peptide chains to increase terminal bonds.
Exopeptidases remove terminal amino acids.
Didpeptidases hydrolyse dipeptides into amino acids

Question 2

Compare endopeptides and exopeptidases

Answer 2

Endopeptidases hydrolyse internal peptide bonds.
Exopeptidases remove amino acids at the ends.
More terminal bonds for exopeptidases to hydrolyse

Question 4

Describe the action of membrane bound dipeptidases and explain their importance

Answer 4

Hydrolyse peptide bonds to release amino acids.
Amino acids can cross cell membrane by facilitated diffusion.

Question 5

Describe the complete digestion of starch by a mammal

Answer 5

Hydrolysis of glycosidic bonds.
Starch maltose by amylase.
Maltose to glucose by disaccharidase.
Disaccharidase is membrane bound.

Question 6

Function of bile salts and micelles

Answer 6

Bile salts emulsify lipids forming droplets which increase surface area for lipase to hydrolysis.
So faster hydrolysis of triglycerides or lipids.
Micelles carry fatty acids and monoglycerides to intestinal epithelial cell

Question 7

Describe lipid digestion

Answer 7

Lipase hydrolysis triglycerides, by breaking ester bonds.
Form monoglycerides and fatty acids.

Question 8

Explain the advantage of emulsification and micelles formation

Answer 8

Droplet increase surface area for lipase, so faster hydrolysis of triglycerides or lipids.
Micelles carry fatty acids and monoglycerides through membrane to intestinal epithelial cell

Question 9

Describe and explain 2 features you would expect t find in a cell speicalised for absorption

Answer 9

Microvilli so large surface area for absorption.
Larger number of co-transporter , protein carrier, channel protein so faster rate of absorption.
Larger number of mitochondria so make more ATP by respiration.
Membrane-bound digestive enzyme so maintain concentration gradient for faster absorption.

Question 10

Describe the process involved in the absorption and transport of digested lipid molecules from ileum into lymph vessels

Answer 10

Micelles contain bile salts and fatty acids.
Make fatty acids and monoglycerides more soluble in water.
Fatty acids and monoglycerides absorbed by simple diffusion.
Triglycerides reformed in cells.
Vesicles move to membrane for exocytosis

Question 11

Describe the role of micelles in the absorption of fats into the cells lining the ileum

Answer 11

Micelles include bile salts and fatty acids.
Make fatty acids more soluble in water.
Release fatty acids to the lining of the ileum

Question 12

How is the Golgi body involved in the absorption of lipids

Answer 12

Modifies triglycerides .
Combine triglycerides with protein .
Pack in a vesicle and exocytosis.

Question 13

Explain how monosaccharides and amino acids are absorbed into blood

Answer 13

Some by facilitated diffusion when higher concentrations in lumen.
Sodium ions actively transported from ileum cell to blood.
Maintains concentration gradient for sodium ions to enter cel by facilitated diffusion and boring with a molecule of glucose by co-transport.
Facilitated diffusion of glucose in blood.

Question 15

Explain how digestion of starch in gut leads to an increase in the concentration of glucose in the blood.

Answer 15

Hydrolyse by amylase.
Produce glucose in the gut.
Small enough cross gut wall into blood.