3.3.3 Digestion And Absorption

Question 1

What is digestion?

Answer 1

hydrolysis of large molecules into smaller molecules that can be absorbed across the cell membrane

Question 2

Which enzymes are involved in carbohydrate

digestion? Where are they found?

Answer 2

● Amylase in mouth
● Maltase, sucrase, lactase in
membrane of small intestine

Question 3

Amylase breaks down ….

Answer 3

starch into smaller polysaccharides

Question 4

maltase breaks down …..

Answer 4

maltose into 2 glucose molecules

Question 5

Sucrase breaks down ….

Answer 5

sucrose into glucose and fructose

Question 6

Lactase breaks down …..

Answer 6

Lactose into glucose and galactose

Question 7

Where are lipids digested?

Answer 7

Small intestine

Question 8

What needs to happen before lipids can be

digested?

Answer 8

They must be emulsified by bile salts
produced by the liver. This breaks down
large fat molecules into smaller, soluble
molecules called micelles, increasing
surface area.

Question 9

How are lipids digested?

Answer 9

Lipase hydrolyses the ester bond
between the monoglycerides and fatty
acids.

Question 10

Which enzymes are involved in protein digestion?

What is their role?

Answer 10

● Endopeptidases= break between specific
amino acids in the middle of a polypeptide.
● Exopeptidases= break between specific amino
acids at the end of a polypeptide.
● Dipeptidases= break dipeptides into amino
acids.

Question 11

How are certain molecules absorbed into the ileum

despite a negative concentration gradient?

Answer 11

Through co-transport.

Question 12

Which molecules require co-transport?

Answer 12

Amino acids and monosaccharides.

Question 13

Explain how sodium ions are involved in

co-transport.

Answer 13

Sodium ions (Na+) are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions.

Question 14

Why do fatty acids and monoglycerides not require

co-transport?

Answer 14

The molecules are nonpolar, meaning they can easily diffuse across the membrane of the epithelial cells.

Question 15

Explain the process of co transport of glucose in the lumen.

Answer 15

• sodium ions are actively pumped from the cytoplasm of the epithelial cells via channel proteins into the surrounding tissue fluid
• sodium ions diffuse from lumen into epithelial cell,down conc gradient carrying the glucose molecules with them.