2.5.10 Humans: Bile

Question 1

What is Bile

Answer 1

Bile is an alkaline substance produced by cells in the liver

• Before being released into the small intestine bile is stored in the gallbladder

Question 2

Exam Tip

Answer 2

Bile contains bile salts, it is these molecules which emulsify the fats, however you can use both terms interchangeably

Question 3

Bile has two main roles, what is the first one

Answer 3

Neutralising the hydrochloric acid from the stomach

• The alkaline properties of bile allow for this to occur
• This neutralization is essential as enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach

Question 4

Bile has two main roles, what is the second one

Answer 4

Breaking apart large drops of fat into smaller ones (and so increasing their surface area)

• This is known as emulsification

Question 5

The more alkaline conditions and larger surface area allows lipase to, do what?

Answer 5

chemically break down the fat (lipids) molecules into glycerol and fatty acids at a faster rate

Question 6

Exam Tip

Answer 6

Emulsification is the equivalent of tearing a large piece of paper into smaller pieces of paper.

This is an example of mechanical digestion, not chemical digestion – breaking something into smaller pieces does not break bonds or change the chemical structure of the molecules which make it up, which is the definition of chemical digestion.