enzymes and digestion

Question 1

explain the 2 processes of physical digestion and why they occur

Answer 1

large pieces are ground up into small pieces by teeth - easier to swallow
the stomach churns - increases surface area for enzymes to act at

Question 2

what happens during chemical digestion

Answer 2

enzymes hydrolyse large macromolecules that are insoluble into smaller soluble molecules

Question 3

name one carboyhydrate

Answer 3

starch

Question 4

explain the process of digestion of starch
( in mouth, stomach, pancreas, ileum)

Answer 4

mouth:
salivary glands produce amylase which hydrolyses starch into maltose by breaking the glycosidic bonds
the salivary glands also produce mineral salts to keep pH at 7

stomach:
contains HCl which denatures amylase

pancreas:
secretes pancreatic juice which contains amylase that hydrolyses the glycosidic bond in starch to form maltose and alkaline salts which maintain pH 7

ileum:
contains the membrane-bound enzyme
maltase which hydrolyses the glycosidic bond in maltose to form alpha glucose

Question 5

what are the products of the hydrolysis of sucrose in the ileum

Answer 5

the membrane bound organelle sucrase hydrolyses the glycosidic bond in sucrose to form fructose and glucose

Question 6

what are the products of hydrolysis of lactose in the ileum

Answer 6

the membrane bound organelle lactase hydrolyses the glycosidic bond in lactose to form galactose and glucose

Question 7

Describe how lipids are digested

Answer 7

Lipases hydrolyse triglycerides (lipids) into monoglycerides and fatty acids
Bile salts emulsify lipids to increase the surface area for enzyme action

Question 8

Describe structure and function of organs of the digestive system

Answer 8

Salivary glands: near mouth. Pass amylase via a duct into the mouth
Oesophagus: carries food from mouth to stomach
Stomach: muscular sac, produces enzymes to digest protein, stores and digests food
Pancreas: gland secreting pancreatic juice containing protease, amylase and lipase
Ileum: long muscular tube, walls and glands secrete enzymes. villi and microvilli to increase surface area
Large intestine: absorbs water
Rectum: stores faeces and egests them via the anus

Question 9

describe the process of the digestion of proteins

Answer 9

endopeptidase
this hydrolyses the peptide bond in the middle of the polypeptide chain forming 2 shorter polypeptides

exopeptidase
hydrolyses the peptide bond at the end of the polypeptide chain forming amino acids and dipeptides

dipeptidase
is a membrane-bound enzyme that hydrolyses the peptide bond in dipeptides to form amino acids

Question 10

Describe emulsification

Answer 10

the splitting of large lipids into small droplets called micelles

Question 11

Describe the role of the liver in lipid digestion

Answer 11

produces bile salts that emulsify fat

Question 12

Name the group of enzymes that hydrolyse proteins

Answer 12

peptidases

Question 13

Explain what is meant by ‘membrane bound disaccharidase’

Answer 13

the disaccharide is bound to the wall of the intestine
rather than being released into the intestine

Question 14

Give 3 examples of disaccharidases

Answer 14

sucrase
maltase
lactase