Enzymes Flashcards Preview

Science for Med Revision > Enzymes > Flashcards

Flashcards in Enzymes Deck (29):
1

Ribozymes?

- Catalytic RNA molecules
- No protein component

2

Cofactor?

Non protein component required for activity

3

Co enzyme?

Enzyme produced from a vitamin such as FAD or NAD

4

Prosthethic group?

Covalently bound (or very closely associated) cofactor

5

Apoenzyme?

Inactive enzyme that is activated when cofactor binds

6

Holoenzyme?

The whole enzyme

7

Why isn't a spontaneous reaction instant?

Needs an activation energy

8

What is the transition state?

- The instantaneous moment new chemical bonds are formed and old are broken
- From this point the reaction can go back to reactants or become products

9

What type of bonds occur between substrate and enzyme

Non covalent

10

What is the active site complementary to?

Transition state

11

In what 3 ways do enzymes reduce activation energy?

- Reduce entropy
- Desolvation
- Induced fit

12

How does reducing entropy reduce the activation energy?

Increases chance that substrates collide in the proper orientation

13

How does desolvation lower activation energy?

H bonds with substrate/solution replaced by H bonds with substrate/enzyme

14

What is the michaelis-menton equation?

E + S ES ----> P

15

In the reversible step, which reaction is slower?

Reforming the products

16

What is Km?

The substrate conc. when the reaction v is half the maximum

17

What does Km measure?

The ratio of formation of ES from E + S, compared to the formation of E + S from ES

18

What does Km show you?

The affinity of the enzyme for the substrate

19

What does a large Km tell you?

- ES complex is unstable therefore
- More ES ----> E + S

20

What does glucokinase catalyse?

Glucose + ATP to G-6-P

21

What does an elevated level of creatine kinase allow you to diagnose?

- MI
- Infection

22

What are the 2 reaction mechanisms that an enzyme catalysed reaction with 2 substrates can follow?

- Random w/ ternary complex
- Ordered w/ ternary complex
- No ternary complex

23

What is random with a ternary?

- Either substrate can bind first
- Forms two products

24

Ordered ternary reaction?

- One substrate attaches first, the other follows
- Forms one product

25

What is the mechanism of reaction when no ternary complex forms?

- 2 reactions occurs
- 1st reaction with 1st substrate alters the enzyme and produces a product
- Altered enzyme can now bind to 2nd substrate and produces a second product

26

What type of reactions have no ternary complex formation

Transamination

27

How does pH alter enzyme function

pH will change the charge of amino acids in the sequence and can make the active set stop functioning

28

Effect of a competitive inhibitor on Vmax and Km?

- Vmax same
- Km decreases

29

Effect of a non competitive inhibitor on Vmax and Km

- Vmax decreases
- Km same