B3: Organisation and the Digestive System

Question 1

What is the name of the enzyme which breaks carbohydrates down?

Answer 1

Carbohydrase (amylase).

Question 2

In which part of the digestive system does the carbohydrase work?

Answer 2

In the mouth and the small intestine

Question 3

What are the carbohydrates broken down into?

Answer 3

Sugars (glucose)

Question 4

What is the name of the enzyme which breaks protein down?

Answer 4

Protease (pepsin).

Question 5

In which part of the digestive system does the protease work?

Answer 5

In the stomach and the small intestine

Question 6

What are the proteins broken down into?

Answer 6

Amino acids

Question 7

What is the name of the enzyme which breaks lipids down?

Answer 7

Lipase

Question 8

In which part of the digestive system does the lipase work?

Answer 8

Small intestine

Question 9

What are lipids broken down into?

Answer 9

Fatty acids and glycerol

Question 10

What is the test for sugar?

What is the colour change?

Answer 10

Benedicts solution.

Blue-brick red on heating.

Question 11

What are lipids?

Answer 11

Fats and oils.

Question 12

What is the test for starch?

What is the colour change?

Answer 12

Iodine solution.

From yellow/red to blue/black if starch is present.

Question 13

What is the test for lipids?

Answer 13

Ethanol, gives a cloudy white layer if lipids are present.

Question 14

What are proteins made up of?

Answer 14

Long chains of amino acids.

Question 15

What happens when a protein is denatured?

Answer 15

The bonds that hold proteins together will break and the protein will lose its shape.

Question 16

What is the test for proteins?

Answer 16

Biuret reagent turns from blue to purple.

Question 17

What are enzymes?

Answer 17

Biological catalysts which speed up a reaction, whilst remaining unchanged.

Question 18

What do enzymes control in the body?

Answer 18

Metabolism.

Question 19

How do enzymes speed up reactions?

Answer 19

The substrate of the reaction fits into the active site of the enzyme and they join together (LOCK AND KEY THEORY).

THEY DECREASE THE ACTIVATION ENERGY REQUIRED FOR THE REACTION TO TAKE PLACE.

Question 20

What factors affect enzyme activity?

Answer 20

Temperature and PH.

Question 21

How does the stomach maintain a low pH?

Answer 21

By producing hydrochloric acid so the protease produced there can work.

Question 22

How does the acidic liquid from the stomach become alkaline in the small intestine?

Answer 22

The liver produces alkaline bile.

Question 23

Where is bile produced and stored?

Answer 23

The liver produces bile and bile is stored in the gallbladder.

Question 24

Why is bile important? (give 2 points)

Answer 24

• Bile neutralises the acidity of the food from the stomach and provides alkaline conditions for the enzymes in the small intestine.
• Bile emulsifies (breaks down) the fats in your food into smaller droplets that lipase can act in (bigger surface area).

Question 25

What is the optimum temperature for most enzymes?

Answer 25

37 degrees.