Digestion

Question 1

What is physical digestion and why is it important?

Answer 1

Chewing and squeezing of food in the stomach. Breaks down the food into smaller pieces so that it can pass through the digestive system easily. It increases the surface area which increases the rate of chemical digestion (enzymes)

Question 2

How is food moved along the gut?

Answer 2

By peristalsis, the circular muscles in the gut wall squeeze the food along.

Question 3

Where does chemical digestion take place?

Answer 3

In the mouth, the stomach and small intestine

Question 4

Describe the breakdown of carbohydrates.

Answer 4

It begins in the mouth where starch is broken down to glucose. The pancreas produces carbohydrases which are released into the small intestine and carbohydrates are broken down into small soluble sugars

Question 5

Which enzymes break down proteins?

Answer 5

Proteases

Question 6

What are the breakdown products and lipids and the general name for enzymes which catalyse this reaction?

Answer 6

Lipids are broken down into glycerol and fatty acids. Lipases are the enzymes which speed up this reaction

Question 7

How is the small intestine adapted for efficient absorption of food?

Answer 7

• Very long
• Large surface area because of the microvilli
• Thin lining that reduces diffusion distance for dissolved food molecules
• Good blood supply

Question 8

Describe the breakdown of starch include the name of the enzymes involved

Answer 8

Starch is digested in a 2 step process First amylase breaks down starch to maltose Then maltase breaks down maltose to glucose Amylase and maltase are the enzymes

Question 9

Why is bile needed for the digestion of fat?

Answer 9

Fat is hard to digest because it does not mix well with water. Bile is an emulsifier which allows lipases to work.

Question 10

Where is bile produced, stored and released?

Answer 10

Bile is made in the liver, it is stored in the gall bladder and it is released into the small intestine.

Question 11

Why are the enzymes secreted in the mouth, denatured in the stomach?

Answer 11

The stomach secretes hydrochloric acid, which means the stomach has a pH around 2. This low pH denatures most enzymes including those produced in the mouth. (The proteases produced in the stomach have a low pH optimum)