Module 2: Foundations In Biology: Enzymes 🟢

Question 1

Active site

Answer 1

• unique-shaped part of an enzyme
• binds to a substrate

Question 2

Activation energy

Answer 2

The minimum amount of energy required for a reaction to occur

Question 3

Enzyme-substrate complex

Answer 3

• forms when an enzyme and substrate collide and bind.
• the result is a lowered activation energy

Question 4

Denature

Answer 4

-when the active site changes shape
- this means the substrate can no longer bind

Question 5

Enzyme-inhibitor complex

Answer 5

• when an enzyme and inhibitor collide and bind
• prevents the enzyme-substrate complexes from forming

Question 6

Lock and key hypothesis

Answer 6

• model stating that the enzyme is like a lock and the substrate is a key
• the substrate fits into its enzyme due to the enzymes specific tertiary structure
• they must both be complementary to one another to form an enzyme-substrate complex

Question 7

Induced fit hypothesis

Answer 7

• the enzyme active site changes shape slightly to accommodate the substrate as it binds
• this puts strain on the substrate weakening the bonds
• lowers the activation energy

Question 8

Factors affecting enzymes

Answer 8

• temperature
• pH
• enzyme concentration
• substrate concentration

Question 9

Effect of temperature on rate of reaction

Answer 9

• at low temperatures, there is insufficient kinetic energy for successful collisions
• if the temperature is too high, ionic and hydrogen bonds break, enzymes denature and enzyme substrate complexes cannot form

Question 10

Q10 temperature coefficient

Answer 10

The Q10 temperature coefficient is measure of the rate of change of an enzyme-controlled reaction as a result of increasing the temperature by 10 degrees

Q10= rate of reaction (x+10) degrees / rate of reaction at x degrees

Question 11

Effect of substrate concentration on rate of reaction

Answer 11

• if there is low concentration of substrate , the reaction rate will be lower because fewer collisions will occur
• increasing the substrate concentration increases the rate of reaction
• at high substrate concentrations , the rate of reaction will plateau because all of the enzymes active site are saturated

Question 12

Effect of enzyme concentration on rate of reaction

Answer 12

• at low enzyme concentrations, there will be a lowered activation rate of reaction due to less available enzymes for collisions
• increasing enzyme concentration will increase the rate of reaction as enzyme-substrate complexes are more likely to form
• rate plateaus at high enzyme concentrations due to insufficient availability of substrate

Question 13

Effect of pH on rate of reaction

Answer 13

• enzymes have a narrow optimum pH range
• outside of the range = denaturation

Question 14

Non-competitive inhibitors

Answer 14

• bind to the enzyme away from the active site (allosteric site)
• causing the active site to change shape slightly
• enzyme-substrate complexes cannot form
• rate of reaction is much slower

Question 15

Competitive inhibitors

Answer 15

• competitive inhibitors are a similar shape as the substrate and so, it binds to the active site of the enzyme
• this prevents the substrate from binding
• most competitive inhibitors are reversible
• once the inhibitor is removed, the reaction rate increases

Question 16

End-product inhibition

Answer 16

• a type of negative feedback where the final product of a metabolic pathway binds to an allosteric site on an enzyme earlier in the pathway.
• This inhibits the enzyme, slowing or stopping the reaction.
• It helps prevent overproduction , saving energy and maintaining balance
- prevents waste

Question 17

Coenzymes and cofactors

Answer 17

• coenzymes are organic molecules , cofactors are inorganic molecules
• their function is to bind to the active site of an enzyme to make it complementary to the substrate
• the inactivated protein is called an apoenzyme
• when it is activated by the binding of the cofactors, it is called the holoenzyme

Question 18

Metabolic poison

Answer 18

Substance that damages cells by interfering with metabolic reactions . Usually an inhibitor

Question 19

How do some medicinal drugs act as inhibitors

Answer 19

Penicillin: non-competitive inhibitor of transpeptidase to prevent formation of peptidoglycan cross-links in bacterial cell wall.
Ritonavir: inhibits HIV protease to prevent assembly of new virions

Question 20

What is an Enzyme?

Answer 20

An enzyme is a biological catalyst that speeds up the rate of a chemical reaction without being used up, by lowering the activation energy of the reaction.
- usually a globular protein
- It has a specific tertiary structure that determines the shape of its active site, which is complementary to its substrate.