Enzymes Flashcards
Do enzymes impact the thermodynamics of a biological reaction?
No, delta H_rxn and the equilibrium position do not change
What do enzymes do?
- Lower the activation energy
- Increase the rate of the reaction
- Are not changed or consumed in the reaction (will appear in the reactants and the products)
- Are pH and temperature sensitive, optimal activity at specific pH ranges and temperatures
- Do not affect the overall deltaG of the reaction
- Are specific for a particular reaction or class of reactions
Oxidoreductases?
Catalyze oxidation-reduction reactions, transfer electrons between biological molecules, often have cofactors that serve as electron carriers, like NAD+ or NADP+; electron donor = reductant; electron acceptor = oxidant
transferases?
catalyze the movement of a functional group from one molecule to another, ex. kinases
kinases?
catalyze the transfer a phosphate group, generally from ATP, to another molecule
Hydrolases?
Catalyze the breaking down of a compound into two molecules using the addition of water, ex. phosphatase, cleaves a phosphate group from another molecule
Lyases?
Catalyze the cleavage of a single molecule into two products, don’t require water, don’t act as oxidoreductases, can also catalyze the reversal (two molecules into a single molecule), in that case would be called a synthase
LIL’HOT
Major enzyme classifications
- Ligase
- Isomerase
- Lyase
- Hydrolase
- Oxidoreductase
- Transferase
Isomerases?
Catalyze the rearrangement of bonds within a molecule, can catalyze reactions between stereoisomers as well as constitutional isomers
Ligase?
Catalyze addition or synthesis reactions, generally between large similar molecules and often require ATP, often with nucleic acid synthesis and repair on Test Day
Endergonic reaction?
One that requires energy input, deltaG>0
Exergonic reaction?
One where energy is given off, deltaG< 0
If a reaction is spontaneous, deltaG is
negative
How do catalysts impact activation energy?
They lower it
The molecule upon which an enzyme acts is known as its…?
Substrate
The location where the substrate is held during its chemical reaction is known as the
active site