3.3 Digestion and absorption

Question 1

Define digestion

Answer 1

The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across the cell membrane.

Question 2

Which enzymes are involved in carbohydrate digestion and where are they found?

Answer 2

amylase- mouth

maltase, lactase, sucrase- small intestine

Question 3

what are the substrates and products of carbohydrate digestive enzymes?

Answer 3

amylase- smaller polysaccharide chains
maltase- maltose into 2 a- glucose
sucrase- sucrose into a-glucose and fructose
lactase-lactose into a-glucose and galactose

Question 4

Where are lipids digested?

Answer 4

in the small intestine

Question 5

What needs to happen to the lipids before they are digested

Answer 5

They need to be emulsified by bile salts which are produced in the liver. These break down large insoluble lipids into smaller soluble molecules called micelles which increase the surface area.

Question 6

How are lipids digested?

Answer 6

Lipase hydrolyses the ester bond which breaks the lipid between monoglycerides and fatty acids.

Question 7

What enzymes are involved in protein digestion and what are their roles?

Answer 7

Hydrolysis of peptide bonds
Endopeptidase breaks the polypeptide chain into smaller chains
Exopeptidase breaks down terminal amino acids
Dipeptidase breaks the peptide bond between dipeptides

Question 8

How are certain molecules absorbed into the ileum despite a negative concentration?

Answer 8

Through co-transport

Question 9

Which molecules require co-transport

Answer 9

Amino acids and monosaccarides

Question 10

Explain how sodium ions are involved in co-transport?

Answer 10

Sodium ions are actively transported out of the cell and into the ileum and then nutrients are then taken into the cell along with the sodium ions.

Question 11

Why do fatty acids and monoglycerides not require co-transport

Answer 11

They are non-polar