Enzymes

Question 1

Globular proteins (Structure)

Answer 1

Complex, ball like

Question 2

Fibrous proteins (Structure and Function)

Answer 2

Simple, struture is function

Question 3

What are Enzymes made of

Answer 3

Proteins + RNA molecules

Question 4

How much can enzymes increase the rate of reaction by?

Answer 4

10^17

Question 5

Examples of enzyme action

Answer 5

Food Breakdown (Hexokinase), Biosynthesis (Polymerase)

Question 6

Phenylketorunia (PKU)

Answer 6

• Mutation in Phenylalanine Hydroxylase
• Toxic build up in brain -> intelectual disabilities + seizures

Question 7

McArdle Disease

Answer 7

Genetic Disorder, affects skeletal muscle, deficiency in myophosphorylase

Question 8

Components of Active site

Answer 8

Binding Site = Binds and orients substrate
Catalytic site = Reduce chemical activation energy

Question 9

Active site properties and abilities

Answer 9

• Non - polar
• hydrogen bonding, Hydrophobic interactions, van der Waals, electrostatic, reversible covalent bonding

Question 10

What is the allosteric site

Answer 10

Distinct from active site, induces a conformational change (change in active site)
Mechanism of regulation (Activates or inhibits reactions)
Can act as a feedback mechanism

Question 11

What is a Cofactor

Answer 11

Any inorganic factor required for enzyme activity or protein function

Question 12

What is a Coenzyme

Answer 12

An organic cofactor which is directly involved in enzyme catalysed reactions

Question 13

What is a prosthetic group

Answer 13

Covalently associated non-protein constituent for a particular function

Question 14

What is unique to a metalloenzyme

Answer 14

Cannot function without a metal ion in the active site (Example of a cofactor)

Question 15

Co-Enzymes

Answer 15

• Required by some enzymes of (optimal) activity
• Typically organic molecules
• Contains functionaliteis not found in proteins
• Transiently bound (Not permenant)
• May be altered during reaction - renewal

Question 16

A Holoenzyme is formed up of (2 things)

Answer 16

Apoenzyme (inactive Enzyme)+ Cofactor

Question 17

Function of enzyme group: Oxioreductase

Answer 17

Transfer of oxygen or hydrogen atoms or electrons from one substrate to another

Question 18

Function of enzyme group: Transferases

Answer 18

Trasnfers functional groups from one substrate to another

Question 19

Function of enzyme group: Hydrolases

Answer 19

Hydrolysis of a substrate

Question 20

Function of enzyme group: Lyases

Answer 20

Addition or removal of a group to form a double bond

Question 21

Function of enzyme group: Isomerases

Answer 21

Transfer of groups between a molecule

Question 22

Function of enzyme group: Ligases

Answer 22

Bond formation coupled with ATP hydrolysis

Question 23

What is an exergonic reaction?

Answer 23

Spontaneous, produces more energy than input energy (Heat is released)
(-ΔG)

Question 24

What is an endergonic reaction?

Answer 24

Requires more energy input than it yields (Heat is absorbed)
(+ΔG)

Question 25

What is the activation energy

Answer 25

The initial energy required for a reaction (Exer or Endergonic) to occur

Question 26

What do enzymes do to the activation energy?

Answer 26

Reduce it

Question 27

What is the difference in activation energy called?

Answer 27

The Transition State

Question 28

What are the four main catalytic mechanisms?

Answer 28

- Metal Ion - Catalysis by approximation - Covalent Catalysis - Acid Base Catalysis

Question 29

What does Catalysis by approximation do?

Answer 29

Brings substrate together

Question 30

What is V0

Answer 30

-Enzyme Velocity @ Time 0

Question 31

Properties of V0

Answer 31

>10% of Substrate converted fastest rate Least amount of product created Least amount of feedback inhibition

Question 32

Relationship between V0 and S

Answer 32

Higher S = Higher V0

Question 33

What is Km

Answer 33

Vmax/2 on the substrate concentration axis Measure of enzyme affinity for substrate Measure in units of concentration

Question 34

What does high Km indicate in terms of enzyme biding?

Answer 34

Weak binding -> Low affinity

Question 35

What does low Km indicate in terms of enzyme binding

Answer 35

Strong binding -> High affinity

Question 36

What happens when affinity increase (V0, rate of reaction)

Answer 36

Greater V0, therefore faster rate of reaction

Question 37

Small deviations in pH result in?

Answer 37

Much smaller activity

Question 38

What are competitive inhibitors?

Answer 38

Take the place of the substrate in the enzyme -> reduces rate of activity

Question 39

How can competitve inhibitors be overcome?

Answer 39

Increasing Substrate concentration

Question 40

What does a competitive inhibitor do to Vmax and Km

Answer 40

Vmax, remains unchanged Km, increases so enzyme affinity for substrate is reduced

Question 41

What are non competitive inhibitors?

Answer 41

Inhibitors that bind in the allosteric site, changing the shape of the active site Results in substrate not being able to bind

Question 42

What do competitive inhibitors do to Vmax and Km

Answer 42

Vmax is decreased, resulting in a decrease for Vmax/2 Km does not change however

Question 43

What is uncompetitive inhibition and how does it affect Vmax and Km

Answer 43

Inhibitor binds only to the enzyme/substrate complex Decreases both Vmax and Km

Question 44

Other methods of enzymatic regulation

Answer 44

-Reversible covalent Modification -Proteolytic ActivationZymogen -Activation by Proteolytic cleavage -Proteolytic activation