🩷 3.1.4.2 Many proteins are enzymes

Question 1

What are enzymes?

Answer 1

It is a protein which is a biological catalysts which lower the activation energy of the reaction it catalyses

Question 2

What is the induced fit model ?

Answer 2

• The enzymes active site and the substrate are not initially complementary
• The active site moulds around the substrate, becoming complimentary and putting pressure on the substrates bonds
• The bonds bend and break causing the activation energy of the enzyme to reduce
• Enzyme-substrate complexes are formed

Question 3

What is the lock and key model?

Answer 3

The enzyme active site is initially complementary to the substrate. They bind and form enzyme-substrate complexes.

Question 4

Define active site

Answer 4

The area on the enzyme to which the substrate binds. The active site is only complementary to one substrate. When they bind they form enzyme substrate complexes

Question 5

Define enzyme substrate complexes

Answer 5

These form due to successful collisions between enzymes and substrates

Question 6

Define kinetic energy

Answer 6

This is the movement energy conferred to particles due to temperature

Question 7

Define successful collisions

Answer 7

Collisions which result in enzyme substrate complexes forming

Question 8

Define complementary shape

Answer 8

When the shape of the substrate allows it to fit into the shape of the enzymes active site

Question 9

Define tertiary structure

Answer 9

This defines the shape of the active site

Question 10

Define specific shape

Answer 10

The shape of both the substrate and the enzyme are specific to each other so that no other substrate can bind

Question 11

Define similar shape

Answer 11

Used to describe the relationship between competitive inhibitors and substrates

Question 12

What are the four factors affecting rate of reaction?

Answer 12

• temperature
• concentration of substrate
• concentration of enzyme
• ph

Question 13

Describe what would happen on a graph when temperature changes

Answer 13

When temperature increases, between … and … rate of reaction increases until optimum temperature. Final temperatures between … and … rate of reaction decreases

Question 14

Explain what would happen when temperature changes on a graph

Answer 14

• As temperature increases rate of reaction increases due to the increase in kinetic energy of the molecules
• This means that there are more successful collisions so more enzyme substrate complexes are formed up until the optimum temperature
• After this point, the enzymes denature and bonds break, causing the tertiary structure to change
• The active site is no longer complementary to that of the substrate so no more enzyme substrate complexes are formed

Question 15

Describe what would happen on a graph when ph changes

Answer 15

As ph increases between … and … rate of reaction increases. After the optimum ph … rate of reaction decreases

Question 16

Explain what would happen when ph changes on a graph

Answer 16

• At low Ph there is a high concentration of hydrogen ions (H+) which are also known as protons.
• These break the hydrogen/ionic bonds causing the tertiary structure to change and making the active site no longer complementary to the substrate.
• This means that there are less enzyme substrate complexes formed
• After the optimum ph, as the ph increases the concentration of hydroxyl ions (OH) increases
• These also break the hydrogen/ionic bonds causing the same effect as the protons

Question 17

Describe the effect of substrate concentration on graphs

Answer 17

As substrate concentration increases, the initial rate of reaction increases. The rate of reaction then plateus

Question 18

Explain the effect of substrate concentration on a graph

Answer 18

• Initially the rate of reaction increases as the increase in substrate concentration causing as increases in the number of enzyme substrate complexes formed
• The rate of reaction then plateaus because enzymes become the limiting factor as all of there active sites have become saturated

Question 19

Describe the effect of enzyme action on a graph

Answer 19

As enzyme concentration increases rate of reaction increases

Question 20

Explain the effect of enzyme concentration on rate of reaction

Answer 20

• Increasing enzyme concentration increases the rate of reaction as more enzyme substrate complexes are formed however in reality, enzyme concentration would not exceed that of the substrate

Question 21

Describe and explain the effect of a competitive inhibitor

Answer 21

• The competitive inhibitor and the substrate are a similar shape
• They can both (separately) bind to the enzymes active site and compete to do so
• The higher the concentration of the competitive inhibitor, the fewer enzyme substrate complexes formed

Question 22

Describe and explain the effect of a non competitive inhibitor

Answer 22

• The non competitive inhibitor binds to the enzyme away from the active site
• This changes the shape of the active site as it changes its tertiary structure
• The substrate is no longer complementary to the active site so no enzyme substrate complexes can be formed

Question 23

On a graph with competitive inhibitor, non competitive inhibitor and normal enzyme, which inhibitor would catch up to the normal enzyme with increasing substrate?

Answer 23

Competitive inhibitor

Question 24

Which inhibitor cannot be overcome by increasing substrate concentration and why?

Answer 24

Non competitive inhibitor due to it causing a change in the shape of the active site