Enzymes

Question 1

What are enzymes?

Answer 1

Enzymes are biological catalysts that speed up metabolic reactions in living organisms.

Question 2

How would you speed up a chemical reaction in a laboratory setting?

Answer 2

• Raising the temperature
• Increasing the pressure

Question 3

Define anabolic

Answer 3

These reactions build up or synthesise large polymers.

Eg. Cellulose for cell walls

Question 4

Define catabolic

Answer 4

These reactions break down large organic molecules

Eg. Digestion of organic material such as starch to its monomer glucose

Question 5

Where do enzymes function?

Answer 5

Intercellularly and extracellularly

Question 6

Why are enzymes important?

Answer 6

In order to sustain life chemical reactions must occur rapidly. Without enzymes they would occur too slowly.

Question 7

The number of reactions that an enzyme molecule can catalyse per second is called its __________ _______.

Answer 7

Turnover number

Question 8

What type of protein are enzymes?

Answer 8

Enzymes are globular proteins

This means they are soluble in water because of the hydrophilic nature of the side groups of their amino acids.

Question 9

What happens to catalysts after the reaction?

Answer 9

Catalysts remain unchanged and can be used again

Question 10

Give examples of digestive enzymes

Answer 10

Protease
Amylase

Question 11

What does protease digest?

Answer 11

Proteins

Question 12

What does carbohydrase digest?

Answer 12

Carbohydrates

Question 13

What does lipase digests?

Answer 13

Lipids

Question 14

What does cellulase digests?

Answer 14

Cellulose

Question 15

What is catalase?

Answer 15

Catalase is an intracellular enzyme that protects cells from damage by breaking down hydrogen peroxide to water and oxygen.

Question 16

Why do white blood cells use catalase?

Answer 16

White blood cells use catalase to kill microbes once they are ingested.

Question 17

What is a metabolic pathway?

Answer 17

A metabolic pathway is a series of consecutive reactions with each step being catalysed by a different enzyme that is specific for the substrate produced.

Question 18

What happens to the metabolic pathway if one enzyme can’t function?

Answer 18

If one enzyme can’t function, the metabolic pathway cannot run

Question 19

What are the reactants, intermediaries and products known as?

Answer 19

Metabolites

Question 20

Are metabolic pathways anabolic or catabolic?

Answer 20

They can be both anabolic and catabolic

Question 21

What is the name of the energy required for a reaction to start?

Answer 21

Activation energy

Question 22

Name two examples of metabolic pathways

Answer 22

Respiration and photosynthesis are both examples of complex metabolic pathways

Question 23

How does enzyme concentration affect the rate of reaction?

Answer 23

As the enzyme concentration increases so does the rate of reaction as substrates have more active sites to bind to

Question 24

How does substrate concentration affect the rate of reaction?

Answer 24

As substrate concentration increases so does the rate of reaction as more enzyme-substrate complexes are formed

Question 25

What is an enzyme inhibitor?

Answer 25

An inhibitor slows down or stops a reaction by affecting the binding of substrates to enzymes. Can be reversible and irreversible

Question 26

How do reversible inhibitors work?

Answer 26

They bind to the active site through hydrogen bonds and weak ionic interactions therefore they don’t bind permanently

Question 27

What are competitive inhibitors?

Answer 27

They are similar in structure to the substrate molecule therefore they can bind to the active site of an enzyme. They decrease the activity as the compete with substrates for the active site however they don’t affect the yield of product formed

Question 28

What are competitive inhibitors?

Answer 28

They are similar in structure to the substrate molecule therefore they can bind to the active site of an enzyme. They decrease the activity as the compete with substrates for the active site however they don’t affect the yield of product formed

Question 29

What are non-competitive inhibitors?

Answer 29

They don’t bind to the active site but instead bind to the allosteric site. Binding of non-competitive inhibitors change the shape of the active site affecting the binding of the substrate

Question 30

What are coenzymes?

Answer 30

They are organic cofactors which do not bind permanently. They facilitate the binding of substrate to enzyme

Question 31

What conditions affect the rate of enzyme-controlled reactions?

Answer 31

Temperature pH Enzyme conc. Substrate conc.

Question 32

What are the difference between reversible and non-reversible inhibitors?

Answer 32

Reversible means the inhibitor can be removed whereas non-reversible means the inhibitor cannot be removed from the enzyme

Question 33

What is end-product inhibition?

Answer 33

The products of some reactions can act as reversible inhibitors for the enzymes involved, controlling the reaction