Biology - Review Qns - 4.1 & 4.2

Question 1

Inhibition

4 characteristics

Answer 1

Depending on bond strength:

Reversible

Irreversible

Depending on binding point:

Competitive

Non-competitive

Question 2

Cofactors

Answer 2

Cofactors are additional components required by some enzymes to catalyse a reaction.

Question 3

Can enzymes be reused?

Answer 3

As enzymes do not form part of the product of the reaction they catalyse, they are not used up and can be reused over and over again.

Question 4

Non-competitive inhibition

Answer 4

The inhibitor binds to a site of the enzyme that is not the active site (an allosteric site)

Changes the shape (or conformation) of the enzyme

thereby

It affects the binding of substrate to the active site

or

It blocks the changes in shape needed for the reaction to progress once the substrate is bound.

Question 5

Reversible inhibition

2 Points

Answer 5

The bonds formed between inhibitor and enzyme are weak and easily broken, so the inhibition is reversible.

Reversible inhibition can be partially overcome by increasing the concentration of substrate.

Question 6

What major factors affect the rate of enzymatic reactions?

3 factors

Answer 6

Temperature

pH

Concentration

Question 7

What is

A biochemical pathway

Answer 7

A biochemical pathway is a sequence of biochemical reactions catalysed by different enzymes, in which the product of each reaction becomes the substrate in the next reaction.

Question 8

How many models are there of enzyme-substrate reaction?

Answer 8

Two

• The lock and key model
• The induced-fit model

Question 9

Coenzymes

3 points

Answer 9

Coenzymes are small, non-protein organic cofactors such as vitamins, ATP, NADH and NADPH.
Coenzymes are needed for reactions in biochemical pathways, including cellular respiration and photosynthesis.
Coenzymes carry chemical groups, protons and electrons between reactions in order to transfer energy between them.

Question 10

What is the active site?

Answer 10

The active site is a three-dimensional pocket-like part of the enzyme that is shaped to interact with its specific substrate.

Question 11

Describe

Catabolic reactions

Answer 11

Catabolic reactions are reactions in which substrates are broken down and energy is released.

Question 12

Affect on enzyme reaction of:

Temperature

Answer 12

High temperatures can alter an enzyme’s three-dimensional structure and change the shape of the active site. This means the enzyme cannot act as a catalyst.

This change is called denaturation.

Question 13

What is

Metabolism

Answer 13

Metabolism is the collection of all the biochemical (or metabolic) reactions that occur in living cells.

Question 14

Describe

Enzymes

Answer 14

Most enzymes are globular proteins that have a tertiary or quaternary structure.

Question 15

Describe

Anabolic reactions

Answer 15

Anabolic reactions are reactions in which larger molecules are produced from smaller substrates. They require an input of energy

Question 16

What is Activation Energy?

Answer 16

Activation energy is the amount of energy input required for a reaction to start.

Question 17

Affect on enzyme reaction of:

pH

Answer 17

Enzymes have an optimum pH range and if the enzyme is exposed to a pH outside its tolerances, the enzyme may become denatured.

Question 18

Unloaded coenzymes

Answer 18

Unloaded coenzymes accept a chemical group, proton or electron.

Question 19

competitive inhibition

Answer 19

The inhibitor binds to the active site of the enzyme, blocking the substrate from binding

Question 20

Describe

The induced-fit model

(of enzyme–substrate interaction)

Answer 20

The induced-fit model states that when a substrate binds to the active site of an enzyme, the active site can alter its shape to better ft the shape of the substrate.

Question 21

Affect on enzyme reaction of:

Concentration

Answer 21

The concentrations of enzymes and their substrates will have an effect on the rate of a reaction, as both substrate and enzyme are required for the reaction to occur.

Question 22

Loaded coenzymes

Answer 22

Loaded coenzymes donate a chemical group, proton or electron.

Question 23

Irreversible inhibition

Answer 23

The bonds formed between inhibitor and enzyme are strong, so the binding is irreversible.

If the inhibition is irreversible increasing substrate concentration will have no effect.

Question 24

What happens when enzymes and substrates interact?

Answer 24

When enzymes and substrates interact, they form an enzyme–substrate complex.

Question 25

What does an enzyme control

Answer 25

Enzymes control metabolism through the regulation of biochemical reactions at every step of a biochemical (or metabolic) pathway.

Through enzyme regulation, a whole biochemical pathway can be regulated.

Question 26

Phosphorylation and dephosphorylation

Answer 26

Both change the structure (or conformation) of proteins, and therefore both can regulate enzymes.

Question 27

Major factors that determine whether enzymatic reactions can occur

4 factors

Answer 27

Inhibitors

Phosphorylation

Cofactors

Coenzymes.

Question 28

How many types of Metabolic reactions are there?

Answer 28

Two

Catabolic

Anabolic

Question 29

Describe

‘Lock and Key’ model

(of enzyme–substrate interaction)

Answer 29

The lock and key model states that the substrate fts into the active site like a key fits into a lock.

Question 30

Enzymes are:

2 Points

Answer 30

• Often specific to particular substrates, and therefore catalyse specific reactions
• biological catalysts that increase the rate of reactions by lowering the activation energy needed for reactions to occur.

Question 31

Coenzymes ‘loading’

Answer 31

Coenzymes can be

• unloaded or loaded
• and cyclically load and unload: