Digestion & Absorption

Question 1

What is digestion?

Answer 1

Large molecules are hydrolysed by enzymes to produce smaller molecules that can be absorbed.

Question 2

In the mouth, what is starch broken down into and by what enzyme?

Answer 2

Starch is broken down into maltose by salivary amylase (chewing also breaks food into smaller particles increasing surface area for amylase to act upon).

Question 3

In the small intestine, what is starch broken down into by what enzyme?

Answer 3

Starch is broken down into maltose by pancreatic amylase released by the pancreas (in pancreatic juice) into the small intestine.

Question 4

How is maltose hydrolysed? Where?

Answer 4

By maltose into alpha glucose molecules, in the ileum.

Question 5

What can the disaccharide enzymes be referred to as and why?

Answer 5

Membrane-bound disaccharidases as they are part of the cell-surface membrane of the epithelial cells lining the ileum.

Question 6

Which enzymes hydrolyse which disaccharides into what?

Answer 6

Maltase: maltose into 2x a-glucose
Lactase: lactose into glucose + galactose
Sucrase: sucrose into glucose + fructose.

Question 7

What are the products of lipid hydrolysis?

Answer 7

Glycerol, fatty acids, and monoglycerides

Monoglycerides consist of glycerol and one fatty acid.

Question 8

Which enzyme is responsible for the hydrolysis of lipids?

Answer 8

Lipase

Lipase hydrolyzes triglycerides by breaking their ester bonds.

Question 9

Where is lipase secreted from?

Answer 9

The pancreas

Lipase is secreted into the small intestine.

Question 10

What bonds does lipase hydrolyse in triglycerides?

Answer 10

Ester bonds

The hydrolysis of these bonds releases fatty acids.

Question 11

How do bile salts affect the hydrolysis of lipids?

Answer 11

They increase the rate of hydrolysis

Bile salts emulsify lipids, forming small droplets.

Question 12

What is the role of bile salts in lipid digestion?

Answer 12

Emulsification

Emulsification increases the surface area for lipase action.

Question 13

What is emulsification?

Answer 13

A physical process that creates small droplets of lipids

Emulsification does not cause chemical breakdown of lipids.

Question 14

True or False: Emulsification causes chemical breakdown of lipids.

Answer 14

False

Emulsification is solely a physical process.

Question 15

Fill in the blank: Lipase is secreted by the _______.

Answer 15

pancreas

Question 16

What are the three types of enzymes that hydrolyse proteins?

Answer 16

Endopeptidases, exopeptidases, and dipeptidases

These enzymes work together to break down proteins into amino acids.

Question 17

Where are amino acids absorbed in the human body?

Answer 17

Ileum

The ileum is the final section of the small intestine.

Question 18

What initiates the hydrolysis of proteins?

Answer 18

Endopeptidase enzyme in the stomach

This process begins with the action of enzymes that break internal peptide bonds.

Question 19

What is the role of endopeptidases?

Answer 19

Hydrolyse internal peptide bonds to form small polypeptides

This action creates shorter chains of amino acids for further digestion.

Question 20

What is the specific endopeptidase found in the human stomach?

Answer 20

Pepsin

Pepsin functions optimally at a very acidic pH.

Question 21

What is the optimum pH for pepsin to function?

Answer 21

1-2

This acidic environment is maintained by HCl secreted in the stomach.

Question 22

What does HCl do in the stomach?

Answer 22

Provides optimum pH for pepsin

Hydrochloric acid is essential for protein digestion.

Question 23

What type of enzymes does the pancreas secrete for protein digestion?

Answer 23

Exopeptidases

These enzymes act on the ends of polypeptides.

Question 24

What do exopeptidases do?

Answer 24

Hydrolyse peptide bonds at the ends of a polypeptide

This process results in the release of individual amino acids or dipeptides.

Question 25

What is the final stage of protein digestion?

Answer 25

Hydrolysis of dipeptides into two single amino acids ## Footnote This is facilitated by dipeptidase enzymes.

Question 26

Where are dipeptidases located in the human body?

Answer 26

In the microvilli of the epithelial cells of the ileum ## Footnote Dipeptidases are membrane-bound enzymes crucial for the final digestion step.

Question 27

How does the combined action of endopeptidases and exopeptidases increase the efficiency of protein hydrolysis.

Answer 27

True ## Footnote Endopeptidases hydrolyse peptide bonds in the middle of a polypeptide chain, forming more ends for exopeptidases to act upon.

Question 28

Fill in the blank: Endopeptidases hydrolyse internal peptide bonds in long chains of amino acids to form many _______.

Answer 28

shorter ones ## Footnote This creates more ends for exopeptidases to act on.

Question 29

Adaptations of the ileum for absorption?

Answer 29

1. Long length: large surface area. 2. Villi & microvilli: large surface area. 3. Only 1 layer of epithelial cells: short diffusion pathway. 4. Many mitochondria: supply ATP for active transport. 5. Channel & carrier proteins: absorption of specific molecules via facilitated diff. + active transport.