Enzymes

Question 1

What type of protein are enzymes?

Answer 1

Globular

Question 2

What structure do enzymes have?

Answer 2

Tertiary- complex 3D shape held together by bond (ionic, hydrogen disulphide bridges hydrophobic interactions), determines shape of active site

Question 3

What are enzymes?

Answer 3

Globular proteins act as biological catalysts

Question 4

What’s a biological catalyst?

Answer 4

Something made of living cells which helps speed up the rate of chemical reactions

Question 5

What two types of metabolic reactions do enzymes control?

Answer 5

Anabolic
Catabolic

Question 6

What’s an anabolic reaction?

Answer 6

Building up molecules e.g protein synthesis

Question 7

What’s a catabolic reaction?

Answer 7

Breaking down molecules e.g digestion

Question 8

When a substrate binds to an enzyme what forms?

Answer 8

Enzyme substrate complex

Question 9

What does complimentary shape mean?

Answer 9

Enzymes are specific to their substrate

Question 10

How does an enzyme act on a substrate

Answer 10

It makes temporary bonds at the active site forming an enzyme substrate complex.

Question 11

What does each enzyme do?

Answer 11

It catalyses one specific reaction

Question 12

Why do enzyme only catalyse one specific reaction?

Answer 12

They have a specific 3D tertiary structure (active site is only specific to one substrate)

Question 13

Why does maltase only catalyse maltose in digestion? (3 marks)

Answer 13

Maltase only catalyse maltose in a hydrolysis reaction because it has a specific 3D structure. Therefore the active site will have a specific shape so only maltose (substrate) which has a complimentary shape will bind to the active site to form an enzyme substrate complex.

Question 14

How do reactions occur between enzymes and substrates?

Answer 14

Reactions occur due to collisions which have to be the right orientation and force.

Question 15

Where are enzymes ,add and where do they act?

Answer 15

Intercellular (inside cells)
Extracellular (secreted outside cells)

Question 16

What are the two different theories of how enzyme substrate complexes form?

Answer 16

Lock and key model
Induced fit

Question 17

What does the lock and key model suggest about E-S complexes?

Answer 17

It is an earlier model which suggests enzymes active sites are rigid and permanent

Question 18

Explain the lock and key model

Answer 18

The active site of the enzyme acts as the specific lock while the substrate acts as the key due to it’s complimentary shape. When the substrate binds to the active site an anabolic or catabolic reaction occurs to achieve the products

Question 19

Explain the induced fit model

Answer 19

Before the reaction, the active site is not complimentary to the substrate
As the substrate binds to the active site, it changes shape to better fit / become complimentary to the substrate to form an enzyme substrate complex
This stresses and distorts the bonds in the substrate causing the reaction to occur and products to be released

Question 20

What do enzymes do to cause high rate of reaction?

Answer 20

Lower activation energy

Question 21

How is activation energy lowered and why is it useful?

Answer 21

The stress/distorting of the bonds in the substrate causes the activation energy to be lower
It reduces the minimum energy required to start a reaction.

Question 22

What is a successful collision and what does it cause

Answer 22

It causes a reaction:
- collide with enough energy
- collide with suitable orientation
- substrate must be complimentary to active site
- come into physical contact with a substrate

Question 23

Explain how the active site of an enzyme causes a high rate of reaction?

Answer 23

• lowers activation energy
• induced fit = active site changes so E-S complex forms causing bonds to be stressed/distorted.