Chapter 8 : Enzyme Kinetics Flashcards
Enzymes
A substance produced by a living organism that acts as a catalyst that brings about a specific biochemical reaction
Why are enzymes so imporant ?
Enzymes control the speed of biochemical reactions to keep the body functioning
The specificity of an enzyme is determined by
It’s active site
How is an enzyme named ?
By adding -ase to the end
What are the six classes of enzymes?
- oxidoreductases
- transferases
- hydrolases
- lyases
- isomerases
- ligases
Oxioreductases
Enzymes used for oxidation reduction reactions
Transferases
Enzymes used for transfer of functional groups
Hydrolases
Enzymes used for hydrolysis reactions
Lyases
Enzymes used for addition of double bonds
Isomerases
Enzymes used for isomerization reactions
Ligases
Enzymes used for the formation of bonds with ATP cleavage
What are cofactors
A non-protein chemical compound of metallic ion that is required for a protein’s biological activity to happen. They can be considered helper molecules
What is a coenzyme ?
Non-protein molecules that participate in catalysis when bonded to the active site of the enzymeTr
True or false, coenzymes are often vitamins or contain vitamins as part of their structure
True
Prosthetic group
When a coenzyme is covalently bonded to the enzyme
Holoenzyme
Contains the catalytically active complex of the protein and the prosthetic group
Apoenzyme
A protein with the catalytically inactive complex but without the prosthetic group
Specificity
Enzyme acts only on a specific substrate; lock and key theory
Induced fit model
The shape of an enzyme’s active site is modified when binding to the substrate -> change in conformation
For a reaction to take place spontaneously, ΔG must be
negative
If a catalyst is present in a reaction , does ΔG change ?
No , ΔG stays the same and depends only on the energy of the reactants and products and respective concentrations.
What can ΔG tell us about the rate of the reaction
ΔG indicates nothing about the rate, only if it will occur spontaneously or not
Free Energy Change Equation
ΔG = ΔG’ +RTln [C][D]/ [A][B]
What does ΔG’ represent ?
the standard free energy change ( the concentration of reactants and products are at constant pressure : 1 atm and constant pH: 7
What does R represent ?
Gas constant
Without catalysts , are reactions favorable ?
No they are usually unfavorable in the environment and tend to be very slow. A catalyst is needed to increase the rate of a reaction
True or False, a chemical reaction will occur if reactions do not have the energy to achieve the transition state
False, reactions will occur if reactants have the energy needed to achieve transition state to undergo rearrangement
The rate of any chemical reaction is proportional to the concentration of the _______ molecules having the ______ state energy
reactant , transition
The higher the _______-_ energy, the less likely that molecules will have this energy and the slower the reaction will occur
transition state
Activation energy ( Ea)
Energy required to raise the average energy of the reactants to transition state energy
What is one way to lower the activation energy
Increase temperature
