3.3- Digestion & Absorption

Question 1

Define digestion

Answer 1

Hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes

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

What are substrates and products of carbohydrate digestive enzymes?

Answer 3

• amylase -> starch into smaller polysaccharides
• maltase -> maltose into 2x glucose
• sucrase -> sucrose into glucose and fructose
• lactase -> lactose into glucose and galactose

Question 4

Where are lipids digested?

Answer 4

The small intestine

Question 5

What needs to happen before lipids can be digested?

Answer 5

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 6

How are lipids digested?

Answer 6

Lipase hydrolyses the ester bonds between monoglycerides and amino acids

Question 7

Which enzymes are involved in protein digestion? What is their role?

Answer 7

• endopeptidases: break between specific amino acids in middle of a polypeptide
• exopeptidases: break between specific amino acids acids at the end of polypeptides
• dipeptidases: break dipeptides into amino acids

Question 8

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

Answer 8

Co-transport

Question 9

Which molecules require co-transport?

Answer 9

Amino acids & monosaccharides

Question 10

Explain how sodium ions are involved in co-transport

Answer 10

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 11

Why do fatty acids and monoglycerides not require co-transport?

Answer 11

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