Digestion

Question 1

On a basic level, what happens during digestion?

Answer 1

Larger molecules (carbohydrates) are broken down by hydrolysis into disaccharides, then monosaccharides.

Question 2

What is physical digestion?

Answer 2

When large food pieces are broken down into smaller pieces by the teeth. This means the food can be ingested and provides a large SA for chemical digestion.

Question 3

What are the three main types of digestive enzyme?

Answer 3

• carbohydrase
• lipase
• protease

Question 4

Amylase is involve in carbohydrate digestion. Where is it produced?

Answer 4

In the mouth and pancreas

Question 5

What does amylase do?

Answer 5

Amylase hydrolysed alternate glycosidic bonds of the starch molecule, to produce MALTOSE.

This maltose is, in time, hydrolysed into a-glucose (monosaccharide) by maltAse.

Question 6

What are the monosaccharide products of maltose?

Answer 6

Glucose + glucose

Question 7

What are the monosaccharide products of sucrose?

Answer 7

Glucose + fructose

Question 8

What are the monosaccharide products of lactose?

Answer 8

Glucose + galactose

Question 9

Maltase (involved in carbohydrate digestion) is a membrane-bound disaccharidase. What does this mean?

Answer 9

It’s an enzyme that attaches to the cell membranes of epithelial cells lining the ileum.

And helps to break down disaccharides (eg maltose) into monosaccharides (glucose). This involves the hydrolysis of glycosidic bonds.

Question 10

Lipids are hydrolysed by ________.

Answer 10

Lipases.

Question 11

Lipases are involved in lipid digestion. What do they involve?

Answer 11

They’re enzymes produced in the pancreas.

They hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides.

Question 12

Lipases hydrolyse triglycerides into fatty acids and monoglycerides. But what are monoglycerides?

Answer 12

A glycerol molecule with a single fatty acid molecule attached

Question 13

How does emulsification help in lipid digestion?

Answer 13

Lipids (fats and oils) are split up into tiny droplets: micelles by bile salts, produced in the liver.

This increases the SA of lipids so that the action of lipases is sped up.

Question 14

What are the three types of proteases (peptidases) involved in protein digestion?

Answer 14

• endopeptidase, exopeptidase, dipeptidase.

Question 15

Outline how endopeptidases are involved in protein digestion.

Answer 15

Endopeptidases hydrolyse the peptide bonds between AAs.

Question 16

Give two example of endopeptidases.

Answer 16

Trypsin.

Pepsin.

Question 17

Outline how exopeptidases are involved in protein digestion.

Answer 17

Exopeptidases hydrolyse the peptide bonds on terminal amino acids.
In this way, they remove single AAs from proteins.

Question 18

Outline how dipeptidases are involved in lipid digestion.

Answer 18

Dipeptidases hydrolyse the bond between the two AAs of a dipeptide.

Question 19

What is the function of amylase in digestion?

Answer 19

Amylase (digestive enzyme) catalyse style conversion of starch (polysaccharide) into maltose (disaccharide). This involves the hydrolysis of the glycosidic bonds in starch.

Question 20

Describe the role of bile salts in lipids digestion.

Answer 20

Bile salts (produced by liver) emulsify lipids, so they form smaller droplets aka micelles which increase SA.

Question 21

How are the products of digestion absorbed?

Answer 21

Across the ileum epithelium into the bloodstream.