E&T: Digestion and Absorption

Question 1

What are carbohydrates broken down by?

Answer 1

Amylase

Membrane-bound disaccharidases

Question 2

Amylase

Answer 2

Digestive enzyme that catalyses the conversion of starch into maltose, which involves the hydrolysis of glycosidic bonds in starch.

Question 3

Where is amylase produced?

Answer 3

By salivary glands and pancrease

Question 4

Membrane-bound disaccharidases

Answer 4

Enzymes attached to cell membranes of epithelial cells lining the ileum which break down disaccharides into monosaccharides.

Hydrolyses glycosidic bonds.

Question 5

What is the disaccharidase for:

• maltose?
• sucrose?
• lactose?

Answer 5

• maltase
• sucrase
• lactase

Question 6

How can monosaccharides be transported across the cell membranes of the ileum epithelial cells?

Answer 6

Via specific transporter proteins

Question 7

What are lipids broken down by?

Answer 7

Lipase

Bile salts

Question 8

Lipase

Answer 8

Enzymes that catalyse the breakdown of lipids into monoglycerides and fatty acids.

Hydrolyses ester bonds.

Question 9

Where are lipases made?

Where do they work?

Answer 9

In pancreas

Work in small intestine

Question 10

Where are bile salts produced?

Answer 10

Liver

Question 11

Bile salts

Answer 11

Emulsify lipids - cause them to form small droplets which increases the SA available for lipases to work on

Question 12

What are proteins broken down by?

Answer 12

Exopeptidases and endopeptidases

Question 13

Once the lipid has been broken down (bile salts), what happens?

Answer 13

Monoglycerides and fatty acids stick to the bile salt to form micelles

Question 14

Endopeptidases

Answer 14

Hydrolyse peptide bonds within a protein.

Question 15

Give an example of an endopeptidase:

Answer 15

Pepsin - released into stomach by cells in stomach lining.

Only works in acidic conditions eg hydrochloric acid in stomach

Question 16

Exopeptidases

Answer 16

Hydrolyse bonds at the ends of protein molecules - remove single amino acids from proteins.

Question 17

Dipeptidases

Answer 17

Exopeptidases that work specifically on dipeptides - act to separate the two amino acids by hydrolysising peptide bonds between them.

Question 18

Where are dipeptidases often located?

Answer 18

Cell-surface membrane of epithelial cells in small intestine

Question 19

Where are the products of digestion absorbed across?

Answer 19

Ileum epithelium into the bloodstream

Question 20

How are these monosaccharides absorbed:

1. Glucose
2. Galactose
3. Fructose

Answer 20

1. Absorbed by active transport with sodium ions via a co-transporter protein.
2. Absorbed the same way as glucose.
3. Absorbed via facilitated diffusion through a different transporter protein.

Question 21

How are glcyerides and fatty acids absorbed?

Answer 21

• Micelles move them towards epithelium.
• As micelles constantly break, they release monoglycerides and fatty acids to be absorbed.
• Lipid-soluble so diffuse directly across epithelial cell membrane.

Question 22

How are amino acids absorbed?

Answer 22

• Via co-transport.
• Sodium ions actively transported out of ileum epithelial cells into blood.
• Creates sodium ion concentration gradient.
• Sodium ions diffuse from lumen of ileum into epithelial cells via sodium-dependent transporter proteins - carry amino acids with them.

Question 23

Digestive enzyme that catalyses the conversion of starch into maltose, which involves the hydrolysis of glycosidic bonds in starch.

Answer 23

Amylase

Question 24

Enzymes attached to cell membranes of epithelial cells lining the ileum which break down disaccharides into monosaccharides.

Hydrolyses glycosidic bonds.

Answer 24

Membrane-bound disaccharidases

Question 25

Enzymes that catalyse the breakdown of lipids into monoglycerides and fatty acids.

Hydrolyses ester bonds.

Answer 25

Lipase

Question 26

Emulsify lipids - cause them to form small droplets which increases the SA available for lipases to work on

Answer 26

Bile salts

Question 27

Hydrolyse peptide bonds within a protein.

Answer 27

Endopeptidases

Question 28

Hydrolyse bonds at the ends of protein molecules - remove single amino acids from proteins.

Answer 28

Exopeptidases

Question 29

Exopeptidases that work specifically on dipeptides - act to separate the two amino acids by hydrolysising peptide bonds between them.

Answer 29

Dipeptidases