Enzymes 1

Question 1

What is an enzyme?

Answer 1

• Globular protein

- Biological catalyst

Question 2

What does an enzyme do?

Answer 2

• Catalyses very high reaction rates
• Shows great reaction specificity
• Work in mild temp/pH conditions
• Can be regulated

Question 3

What is a Ribozyme?

Answer 3

Catalytic RNA molecule with no protein component

Question 4

What is a Cofactor?

Answer 4

Non-protein component needed for activity

Question 5

What is a Coenzyme?

Answer 5

Complex organic molecule, usually produced from a vitamin

Question 6

What is a Prosthetic group?

Answer 6

Cofactor covalently bound to the enzyme or very tightly associated with the enzyme

Question 7

What is a Apoenzyme?

Answer 7

The protein component of an enzyme that contains a cofactor

Question 8

What is a Holoenzyme?

Answer 8

The apoenzyme plus the cofactor(s)

Question 9

What is a Substrate?

Answer 9

Molecule acted on by the enzyme

Question 10

What is an Active Site?

Answer 10

Part of the enzyme in which the substrate binds and is acted upon

Question 11

What does Class 1 Oxidoreductases do?

Answer 11

Transfer electrons

Question 12

What does Class 2 - Transferases do?

Answer 12

Group transfers

Question 13

What does Class 3 - Hydrolases do?

Answer 13

Hydrolysis

Question 14

What do Class 4 - Lyases do?

Answer 14

Form, or add groups to double bonds

Question 15

what do Class 5 - Isomerases do?

Answer 15

Transfer groups within molecules

Question 16

What do Class 6 - Ligases doppelgänger’s?

Answer 16

Formation od C-C, C-S, C-O and C-N bonds

Question 17

What do enzymes not do?

Answer 17

• Move reaction equilibria

- Make a non-spontaneous reaction spontaneous

Question 18

What can enzymes do?

Answer 18

• Increase rate of spontaneous reaction
• Lower the activation energy of biochemical reactions
• Accelerate movement towards reaction equilibrium

Question 19

What is Gibbs free energy?

Answer 19

Useful energy generated from cellular reactions

Question 20

What is true of spontaneous reactions?

Answer 20

They must have -ve ΔG value as they will decrease enthalpy and/or increase entropy

Question 21

What is the energy barrier equal to?

Answer 21

Energy required to position chemical groups correctly

Question 22

What does the transition state represent?

Answer 22

The moment that chemical bonds are formed and broken

Question 23

What is the Binding energy?

Answer 23

When enzymes for non-covalent bonds with substrate molecules allowing them to take the reaction through a different path of reaction intermediates

Question 24

What must the active site be complementary to in order for a reaction to take place?

Answer 24

Transition state

Question 25

What 3 ways do enzymes reduce activation energy?

Answer 25

- Entropy reduction - Desolvation - Induced fit

Question 26

How does entropy reduction reduce activation energy?

Answer 26

- Molecules in free solution will only react by bumping into one another - Enzymes force the substrate to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed

Question 27

How does desolation reduce activation energy?

Answer 27

Weak bonds between the substrate and enzyme essentially replace most or all of the H bonds between substrate and aqueous solution

Question 28

How does induced fit reduce activation energy?

Answer 28

Conformational change occur in the protein structure when he substrate binds

Question 29

How can an enzyme be analysed?

Answer 29

- Enzyme kinetics - Mutagenesis - 3D structure

Question 30

Why does Vmax occur when you increase the amount of substrate?

Answer 30

All of the enzyme activate sites are saturated with substrate

Question 31

What does that model state?

Answer 31

- The first part of the reaction (to produce ES) occurs reversibly - Second part of the equation (to produce E and P) occurs more slowly than the first part

Question 32

What assumptions are made with the Michaelis-Menten equation?

Answer 32

- If 2nd part is slower it must limit the rate of the overall reaction so the overall rate of the reaction must be proportional to the amount of ES - More ES would give higher overall reaction rate and less would give a slower overall reaction rate

Question 33

What is the M-M equation?

Answer 33

Vo = Vmax [S] ____________ Km + [S]

Question 34

What is the M-M equation consistent with?

Answer 34

The experimentally observed dependence of Vo on [S] with the curves shape depending on Vmax/Km at low [S] and depeding on Vmax at high [S]

Question 35

Define Km.

Answer 35

Km is equivalent to the substrate concentration at which the initial reaction rate is half of the maximum reaction rate

Question 36

What do larger Km values indicate?

Answer 36

What do larger Km values indicate?

Question 37

What do smaller Km values indicate?

Answer 37

A more stable ES complex