Enzymes Flashcards
Describe how enzymes work?
Enzymes act upon a molecule called a substrate, this substrate
undergoes conformational changes and forms a product
What are the 2 substrate-complex models?
Lock and key model - a straight fit
Induced fit model - not exact fit, the enzyme active site moulds to a substrate
How do enzymes work on reactions?
Enzymes catalyse reactions meaning they require less free energy to shift a substrate into a transition state
(Enzymes reduce the activation energy and stabilise transition state)
What role do cofactors play?
Many enzymes require cofactors in order to catalyse a reaction
The cofactors can be bound rightly or loosely, loose are bound before and released after
What do transferases,hydrolases and oxioreductases do?
Transferases catalyse group transfers
Hydrolases catalyse hydrolysis reactions
Oxioreductases catalyse oxidation-reduction reactions
What is the initial velocity when referring to enzyme kinetics?
The Vo is the rate of an enzyme catalysed reaction
The first part of the reaction where there is plenty of substrate available and no product
What is the Vmax in reference to enzyme kinetics?
It is the maximum rate of velocity (where enzyme is saturated with substrate and more substrate has no more effect)
What is Km (Michaelis constant)?
It is the substrate concentration which elicits half of the maximum velocity
Why is the substrate concentration less than K typically in the cell?
The substrate concentration is low enough so the enzyme can respond to changes in substrate concentration
What happens to Vmax and Km in response to an increase in substrate concentration?
No change in either
What happens to Vmax and Km in response to an increase in enzyme concentration
Vmax increases (more active site)
No change to Km
How does a competitive inhibitor work and what are effects on Km and Vmax
Occupies the active site preventing an enzyme-substrate complex
The Vmax will stay the same but Km will increase
What are non-competitive inhibitors and what are the effects on Vmax and Km
They do not bind to the active site but interferes with enzymes function instead
Vmax will decrease but Km will stay the same
What is an example of covalent modification?
Phosphorylation where the attachment of a phosphate group to specific amino acids of the enzyme occurs. Catalysed by protein kinases
