Enzymes Flashcards
Define Cofactor:
Non-protein part of an enzyme needed for activity
Define Coenzyme
Complex organic molecule ususally made from vitamins
Prosthetic group:
Cofacter bound to or tightly associated with the enzyme
Apoenzyme:
Protein component of enzyme
What do enzymes do when they catalyze a reaction?
- Reduce activation energy
- Increase rate of spontaenous reactions
- Increase movement toward equilibria
Define a ribozyme?
A type of enzyme with no protein component.
Catalytic RNA molecules
Examples of co-enzyme
FAD
NAD+
Coenzyme A
Holoenzyme?
Entire enzyme, i.e. both apoenzyme & cofactor
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
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
To what state is the active site complementary to?
The molecules transition state
In what 3 ways do enzymes reduce activation energy?
- Induced Fit
- Desolvation
- Entropy reduction
Explain induced fit:
Conformational changes in the enzyme force the substrate together or apart
Explain desolvation:
Strong H bonds bind the solvent & subsstrate together
The enzyme replaces these with weaker substrate-enzyme bonds
Explain entropy reduction:
Enzymes force the substrate into the correct orientation, this way theyre interaction isnt just down to chance
How do we plot enzyme kinetics graphs?
Initial velocity (Vo) Against Substrate conc. (S)
What is Km?
Michaelis Constant
[S] at half the max Vo
Why does Vmax occur?
BEcause all the enzymes active sites are saturated with subtrate
Michaelis-Menton equation:
Vo = (Vmax[S])/(Km+[S])
In what other way do we plot enzyme kinetics?
A lineweaver-Burke plot (doulbe reciprocal)
Whats the equation for lineweaver-burke plots (think straight line):
1/V = (Km/Vmax)(1/[S]) + 1/Vmax
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
What values of Km & Vmax do you want?
An efficient enzyme has a high Vmax & a low Km
