3.1.4.2 Proteins - Enzyme Action

Question 1

How did scientists discover the induced fit model of enzyme action?

Answer 1

They noticed that other molecules could bind to enzymes, which then affected the enzyme’s activity. This led to the conclusion that the enzyme shape must be changing.

Question 2

What is a substrate?

Answer 2

The substance on which an enzyme acts

Question 3

Why are enzymes essential to organisms?

Answer 3

They allow essential chemical reactions to occur rapidly at low temperatures e.g. 37 °C.

Question 4

Enzymes that catalyse chemical reactions outside of cells are called…

Answer 4

extracellular enzymes

Question 5

The functional part of an enzyme is called the…

Answer 5

active site

Question 6

Describe the lock and key model of enzyme action

Answer 6

• A substrate is specific to an enzyme.
• A substrate binds to the active site of an enzyme.
• This lowers the activation energy.
• Product is released from enzyme.

Question 7

Which 3 conditions must be satisfied for a chemical reaction to take place?

Answer 7

• The substrates must collide with sufficient energy to alter the arrangement of their atoms
• The energy of the products must be lower than the substrates.
• The activation energy needs must be met.

Question 8

Which have a higher energy level: substrates or products?

Answer 8

substrates

Question 9

The specific 3D shaped active site of an enzyme is determined by..

Answer 9

its sequence of amino acids (primary structure)

Question 10

Enzymes that catalyse reactions inside of cells are called…

Answer 10

intracellular enzymes

Question 11

When a substrate binds to the active site we call the resulting structure an…

Answer 11

enzyme-substrate complex

Question 12

A substrate does not have the same shape as the active site it has a _____________ shape.

Answer 12

complementary

Question 13

What does the following describe:

• A substrate is specific to an enzyme.
• A substrate binds to the active site of an enzyme.
• This lowers the activation energy.
• Product is released from enzyme.

Answer 13

The lock and key model of enzyme action

Question 14

Hormones are proteins that have a binding site so that they can switch on or off bodily processes. Are they enzymes?

Answer 14

No - many proteins have binding sites or receptor sites. These are not active sites.

Question 15

Which type of biological molecule are enzymes?

Answer 15

Proteins

Question 16

Which structural type of protein are enzymes?

Answer 16

Globular proteins

Question 17

What do we call the initial energy required for a chemical reaction to take place?

Answer 17

Activation energy

Question 18

Define an enzyme

Answer 18

Enzymes are biological catalysts that speed up chemical reactions without being used up or changed.

Question 19

How does a substrate temporarily bind to an enzyme active site?

Answer 19

The substrate temporarily forms bonds with certain amino acids in the active site.

Question 20

What does the following describe:

• Substrate approaches active site
• Enzyme changes shape and forms functional active site.
• Enzyme moulds to substrate
• Change in shape puts a strain on bonds of substrate, lowering activation energy.
• Product is released from enzyme.

Answer 20

The induced fit model of enzyme action

Question 21

What is the name of the currently accepted model of enzyme action?

Answer 21

The induced fit model of enzyme action

Question 22

Describe the lock and key model of enzyme action.

Answer 22

• A substrate is specific to an enzyme.
• A substrate binds to the active site of an enzyme.
• This lowers the activation energy.
• Product is released from enzyme.

Question 23

Why are enzymes still effective even in small amounts?

Answer 23

Because they are not used up or changed so can be used again and again.

Question 24

Describe the induced fit model of enzyme action

Answer 24

• Substrate approaches active site
• active site not complementary/will fit substrate
• active site changes shape and forms functional active site - as substrate binds
• Enzyme moulds to substrate
• Change in shape puts a strain on bonds of substrate, lowering activation energy.

Question 25

Why does formation of enzyme substrate complex increase rate of reaction?

Answer 25

Reduces activation energy

due to the bending/weakening of bonds