Digestion and absorption

Question 1

What is digestion?

Answer 1

Digestion is the hydrolysis of large biological molecules into smaller molecules which can be absorbed across cell membranes.

Question 2

How does Carbohydrates digest in mammals?

Answer 2

Carbohydrates are digested by many different enzymes. Amylases in the mouth digest
larger polymers, maltases in the ileum break down monosaccharides, and sucrases and
lactases break down the dissacharides sucrose and lactose respectively.

Question 3

How does are Lipids digested in mammals?

Answer 3

Lipids are digested by lipases which hydrolyse the ester bond between the
monoglycerides and fatty acid. Before being broken down in the ileum, lipids are
emulsified into micelles by bile salts released by the liver. Emulsification increases the
surface area and speeds up the chemical reaction.

Question 4

How are proteins digested in mammals?

Answer 4

Proteins are digested by enzymes called peptidases of which they are divided into 3 main
groups.

Question 5

Name the 3 types of proteins.

Answer 5

• Endopeptidases
• Exopeptidases
• Dipeptidases

Question 6

What are Endopeptidase?

Answer 6

Hydrolyse peptide bonds between specific amino acids in the middle of a polypeptide.

Question 7

What are Exopeptidases?

Answer 7

Hydrolyse bonds at ends of a polypeptides.

Question 8

What are Dipeptidases?

Answer 8

Break dipeptides into individual amino acids.

Question 9

What are amino acid absorbed by?

Answer 9

Absorbed by facilitated diffusion through specific carrier molecules in the surface membrane of epithelial cells.

Question 10

What do co- transport absorb with sodium?

THIS HAPPENS IN THE ILEUM OF MAMMALS

Answer 10

Amino acid and carbohydrates

Question 11

what are the substrates and products of the carbohydrates digestive enzyme?

Answer 11

Amylase– starch into smaller polysaccharide
Maltase– maltose into 2 times glucose
Sucrase– sucrose into glucose and fructose
Lactase– lactose into glucose and galactose

Question 12

Where are lipids digested?

Answer 12

The small intestine

Question 13

What needs to happen before lipids can be digested?

Answer 13

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 14

How are lipids digested?

Answer 14

Lipase hydrolyses the ester bond between the monoglycerides and fatty acids

Question 15

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

Answer 15

Through co- transport

Question 16

Which molecules require co-transport?

Answer 16

Amino acids and monosaccharides

Question 17

Explain how sodium ions are involved in co-transport.

Answer 17

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 18

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

Answer 18

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