B2 - Digestive Enzymes

What is the function of enzymes in digestion?

Enzymes catalyse (speed up) the breakdown of large food molecules into smaller ones

What type of molecules are enzymes?

Proteins

What is the active site of an enzyme?

A groove on the enzyme's surface where the substrate binds

What is a substrate in an enzyme reaction?

The molecule that the enzyme acts on or breaks down

Why are enzymes described as specific?

Because the substrate must fit exactly into the enzyme's active site

What model is used to describe how enzymes work?

The lock and key theory

What does the lock and key theory show?

The enzyme (lock) only works with a specific substrate (key) that fits its active site

Which enzyme breaks down proteins?

Protease

Where is protease produced?

Stomach, pancreas, and small intestine

What are proteins made of?

Long chains of amino acids

What does protease break proteins into?

Individual amino acids

What happens to amino acids after absorption?

They are joined in a new order to make human proteins

Which enzyme breaks down carbohydrates like starch?

Carbohydrase (specifically amylase for starch)

Where is amylase found?

Saliva and pancreatic fluid

What does starch consist of?

Long chains of glucose molecules

What is the product of starch digestion by amylase?

Simple sugars (e.g. glucose)

Which enzyme breaks down lipids?

Lipase

What is the structure of a lipid molecule?

One glycerol molecule attached to three fatty acid molecules

Where is lipase produced?

Pancreas and small intestine

What are the products of lipid digestion by lipase?

Glycerol and fatty acids

What is bile?

A substance made in the liver and stored in the gallbladder that helps digest lipids

Is bile an enzyme?

No

What does bile do to lipids?

Emulsifies them (breaks large droplets into smaller ones)

Why does emulsifying lipids help digestion?

It increases the surface area, speeding up breakdown by lipase

What is the pH of bile?

Alkaline

What does the alkaline property of bile do?

Neutralises stomach acid and creates alkaline conditions in the small intestine

Why is it important that the small intestine is alkaline?

Because lipase works best in alkaline conditions

Where is bile stored?

In the gallbladder

Where is bile produced?

In the liver