Unit 5

Question 1

What are Enzymes

Answer 1

Proteins that are involved in all metabolic reactions, where they function as biological catalysts

Question 2

What is a catalyst

Answer 2

A substance that increases the rate of a chemical reaction and is not changed by the reaction

Question 3

Enzymes

Answer 3

• Made up of amino acids that join together in a long chain and fold in a specific way.
• Unique enzyme shape is specific to catalyse one particular metabollic reaction

Question 4

The 3 main reactions catalysed by enzymes

Answer 4

• breaking large molecules into smaller ones
• converting one small molecule into another
• building up large molecules from small ones

Question 5

Breaking large molecules into smaller ones

Answer 5

• Digestion
• The nutrients we eat are large and insoluble, we have to break them down into small soluble molecules to be absorbed into the blood in the small intestine

Question 6

Converting one small molecule into another:

Answer 6

Adding or removing groups of atoms

Question 7

Building up large molecules from small ones:

Answer 7

• eg: glucose joined together
• storage molecules eg starch/glycogen inside cells
• or structural molecules eg: cellulose

Question 8

Describe enzyme action

Answer 8

1) enzyme has a unique shape, shape of the active site is complementary to the shape of the substance
2) substrate binds to the enzymes active site to form an enzyme substrate complex
3) enzyme releases the products. It is not used up in the reaction so it is now fine to catalyse another reactiom

Question 9

Which 2 factors affect the rate of enzymes?

Answer 9

pH and temperature

Question 10

Effect of temperature on enzyme activity

Answer 10

When the temperature increases the enzyme activity increases as there is more kinetic energy therefore there are more succseful collisions

Question 11

What is denaturing

Answer 11

+The shape of the active site is changed
- The enzyme active site is mantained by bonds -> at very high temperatures, the bonds in the active site of an enzyme are broken and therefore the active site changes shape
- Active site is no longer complimentary to the substrate molecules -> enzyme won’t work again

Question 12

Effect of pH on enzymes

Answer 12

As the pH increases, so does the enzyme activity until it reaches its optimum pH, from then the enzyme activity decreases as the bonds are broken and enzyme becomes denatured

Question 13

Amylase

Answer 13

A carbohydrase enzyme that breaks down starch to glucose in the mouth and the small intestine

Question 14

Function of hydrochloric acid in gastric juices

Answer 14

• kills harmful microorganisms in food
• It is acidic so the enzyme activity of pepsin is able to work in the stomach

Question 15

Bile

Answer 15

It is produced in the liver and emulsifies fat therefore increases the surface area