Digestion (chapter 6)

Question 1

What is digestion?

Answer 1

the process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed.

Question 2

Oesophagus

Answer 2

carries food from mouth to stomach

Question 3

Stomach

Answer 3

• muscular sac with an inner layer that produces enzymes.
• role: store and digest food, especially proteins.
• has glands that produce enzymes which digest protein.

Question 4

Ileum

Answer 4

• long muscular tube.
• further digests food using enzymes that are produced by its walls and glands.
• inner walls folded into villi then microvilli to give large S.A, which adapts ileum for its purpose of absorbing the products of digestion into the bloodstream.

Question 5

Large intestine

Answer 5

absorbs water, mostly from the secretion of many digestive glands.

Question 6

Rectum

Answer 6

• final section of intestines

- faeces stored before being removed via anus (egestion)

Question 7

Salivary glands

Answer 7

secrete amylase, which hydrolyses starch into maltose.

Question 8

Pancreas

Answer 8

produces secretion called pancreatic juice, which contains:

• proteases to hydrolyse proteins
• lipase to hydrolyse lipids
• amylase to hydrolyse starch.

Question 9

Mechanical digestion

Answer 9

starts in the mouth by using teeth to chew food into smaller, pieces to make it easier to ingest and provides a large S.A for chemical digestion. Food is churned by the muscles in the stomach wall.

Question 10

Chemical digestion

Answer 10

• occurs in the mouth, stomach and small intestine.

- digestive enzymes are released in order to break down large pieces of food into smaller ones.

Question 11

Carbohydrases

Answer 11

hydrolyse carbohydrates, ultimately to monosaccharides

Question 12

Lipases

Answer 12

hydrolyse lipids into glycerol and fatty acids

Question 13

Proteases

Answer 13

hydrolyse proteins, ultimately to amino acids

Question 14

Q: Describe the role of the enzymes of the digestive system in the complete breakdown of starch. [5]

Answer 14

The two enzymes, salivary amylase (made by the saliva) and pancreatic amylase (made by the pancreas) break down starch into maltose by hydrolysing the glycosidic bond. The maltose is then broken down by maltase (made in the small intestine) into glucose.

Question 15

What does salivary amylase break down?

Answer 15

starch into maltose

Question 16

What does pancreatic amylase break down?

Answer 16

the remaining starch into maltose

Question 17

Where is maltase produced?

Answer 17

intestine (by epithelial cells)

Question 18

What does maltase break down?

Answer 18

maltose to a-glucose

Question 19

Why is maltase referred to as a “membrane-bound organelle”?

Answer 19

because it is part of the cell-surface membranes of the epithelial cells that line the ileum

Question 20

What makes sucrase?

Answer 20

villi of epithelium of small intestine

Question 21

What does sucrase do?

Answer 21

hydrolyses the single glycosidic bond in the sucrose molecule to produce glucose and fructose

Question 22

What makes lactase?

Answer 22

intestinal epithelial cells

Question 23

What does lactase do?

Answer 23

hydrolyses the single glycosidic bond in the lactose molecule to produce glucose and galactose

Question 24

What makes lipase?

Answer 24

pancreas

Question 25

What does lipase do?

Answer 25

hydrolyses the ester bond found in triglycerides to form fatty acids and monoglycerides

Question 26

What is a monoglyceride?

Answer 26

a glycerol molecule with a single fatty acid attached

Question 27

What are lipids first split up into?

Answer 27

micelles

Question 28

What splits up lipids into micelles?

Answer 28

bile salts produced by the liver

Question 29

What is the process of lipids being split up known as?

Answer 29

emulsification

Question 30

What does emulsification do?

Answer 30

increases the surface area of the lipids so that the action of the lipases is speeded up

Question 31

What do peptidases (proteases) do?

Answer 31

hydrolyse proteins

Question 32

What do endopeptidases do?

Answer 32

hydrolyse the peptide bond between amino acids in the central region of a protein molecule to form a series of peptide molecules

Question 33

What do endopeptidases produce?

Answer 33

a series of peptide molecules

Question 34

What do exopeptidases do?

Answer 34

hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases to release dipeptides and single amino acids

Question 35

What do exopeptidases produce?

Answer 35

dipeptides and single amino acids

Question 36

What do dipeptidases do?

Answer 36

hydrolyse the bond between the two amino acids of a dipeptide

Question 37

What do dipeptidases produce?

Answer 37

amino acids