Enzymes and Digestion

Question 1

What is a catalyst?

Answer 1

A substance that speeds up chemical change without being changed or consumed during the reaction.

Question 2

What molecules will be joined together to make glycogen?

Answer 2

Glucose.

Question 3

Explain the Lock and Key theory?

Answer 3

The lock and key theory means that whatever shape the substrate is (which in the case acts as the the key) must be complementary to the active site (the lock). This must mean the substrate fits exactly into the active site because enzymes are specific. If the active site is complementary to the shape of the substrate, an ‘Enzyme-Substrate Complex’ can happen. Then as a result of this, the enzyme changes the substrate into the product.

Question 4

Explain the following: enzymes are specific.

Answer 4

Enzymes only bind to one substrate (catalyse one reaction). Active site is only complementary to one substrate. This is determined by the amino acid sequence and the folding of the protein.

Question 5

All reactions require a certain amount of energy to get them started. What is this called?

Answer 5

Activation energy.

Question 6

How do catalysts speed up reactions?

Answer 6

They LOWER the activation energy needed for a reaction.

Question 7

What enzyme reacts with the substrate STARCH and what is the product?

Answer 7

Amylase and the product is glucose. PH=neutral.

Question 8

What enzyme reacts with the substrate FAT (LIPID) and what are the products?

Answer 8

Lipase and the products are: 1 glycerol and 3 fatty acids. pH=acidic.

Question 9

What substrate reacts with the enzyme PROTEASE and what is the product?

Answer 9

Protein and the product is amino acids. pH=acidic.

Question 10

The number of successful collisions between enzymes and substrates will depend on a number of factors: what are they?

Answer 10

• Temperature
• Concentration of enzymes
• Concentration of substrates
• If the active site has been damaged
• If an inhibitor is present

Question 11

What happens the more enzymes there are and why?

Answer 11

The faster the reaction. This is because there are more active sites for the substrates to attach to.

Question 12

Why would the rate of enzyme activity ever level off? What is the limiting factor?

Answer 12

Not enough substrates to bind with the extra enzymes.
Substrate concentration is the limiting factor.

Question 13

What is an inhibitor?

Answer 13

A molecule the blocks the active site but in not broken down. It will prevent the enzyme and the substrate colliding and so will slow down the rate of reaction.

Question 14

What does amylase break down?

Answer 14

Starch.

Question 15

What is digestion?

Answer 15

The breakdown of large insoluble molecules to small soluble molecules that can be absorbed into the blood.

Question 16

What is the name of the enzyme that can cause blood vessels to constrict and become narrower?

Answer 16

Angiotensin Converting Enzyme (ACE)

Question 17

Some enzymes used in washing powders are ‘thermo-stable’.
What is meant by the term ‘thermo-stable’?

Answer 17

They can work over a wide range of temperatures.

Question 18

Many biological washing powders have enzymes, why?

Answer 18

For breaking down difficult to remove stains.

Question 19

What is the commercial use of the enzyme protease?

Answer 19

Used to pre-digest proteins during the manufacture of baby foods and washing powders.

Question 20

What is the commercial use of the enzyme carbohydrase?

Answer 20

Used to convert starch syrup which is relatively cheap into sugar syrup which is more valuable.

Question 21

What does starch agar contain?

Answer 21

Starch.

Question 22

Why is milk agar white?

Answer 22

Because it contains the protein casein.

Question 23

What is the name given to an enzyme that can work at a wide range of temperatures?

Answer 23

Thermostable.

Question 24

What is a benefit of using Thermostable enzymes in things like biological washing powder?

Answer 24

This allows them to be used at a low temperature which save energy and money.

Question 25

What enzyme does saliva contain?

Answer 25

Amylase.

Question 26

Why does it matter that an inhibitor is roughly the same size as the active site?

Answer 26

As it works much better at blocking the substrate.