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Flashcards in Enzymes Deck (23):
1

Define Cofactor:

Non-protein part of an enzyme needed for activity

2

Define Coenzyme

Complex organic molecule ususally made from vitamins

3

Prosthetic group:

Cofacter bound to or tightly associated with the enzyme

4

Apoenzyme:

Protein component of enzyme

5

What do enzymes do when they catalyze a reaction?

- Reduce activation energy
- Increase rate of spontaenous reactions
- Increase movement toward equilibria

6

Define a ribozyme?

A type of enzyme with no protein component.
Catalytic RNA molecules

7

Examples of co-enzyme

FAD
NAD+
Coenzyme A

8

Holoenzyme?

Entire enzyme, i.e. both apoenzyme & cofactor

9

What do these enzyme classes do:
- Oxidoreductases
- Lyases
- Ligases

Oxidoreductases = Transfer electrons
Lyases = Form or add groups to double bonds
Ligases = Form C-C,C-N,C-S,C-O bonds

10

What is gibbs free energy?

Basically the available or useful energy generated from a reaction
Spontaneous reactions have -ve deltaG values because they give out energy

11

To what state is the active site complementary to?

The molecules transition state

12

In what 3 ways do enzymes reduce activation energy?

- Induced Fit
- Desolvation
- Entropy reduction

13

Explain induced fit:

Conformational changes in the enzyme force the substrate together or apart

14

Explain desolvation:

Strong H bonds bind the solvent & subsstrate together
The enzyme replaces these with weaker substrate-enzyme bonds

15

Explain entropy reduction:

Enzymes force the substrate into the correct orientation, this way theyre interaction isnt just down to chance

16

How do we plot enzyme kinetics graphs?

Initial velocity (Vo)
Against Substrate conc. (S)

17

What is Km?

Michaelis Constant
[S] at half the max Vo

18

Why does Vmax occur?

BEcause all the enzymes active sites are saturated with subtrate

19

Michaelis-Menton equation:

Vo = (Vmax[S])/(Km+[S])

20

In what other way do we plot enzyme kinetics?

A lineweaver-Burke plot (doulbe reciprocal)

21

Whats the equation for lineweaver-burke plots (think straight line):

1/V = (Km/Vmax)(1/[S]) + 1/Vmax

22

What does a small Km tell us?

The enzyme-substrate complex is very stable, i.e. the enzyme has a high affinity for its substrate

23

What values of Km & Vmax do you want?

An efficient enzyme has a high Vmax & a low Km