Enzymes Flashcards
What is a cofactor and name an example
A cofactor is a non protein component of an enzyme needed to activate it such as the iron ions in catalase.
What is a conenzyme and name an example
A coenzyme is an organic molecule usually derived from a vitamin such as FAD derived from riboflavin.
What’s the difference between apoenzyme and holoenzyme?
Apoenzyme is just describing the protein part of an enzyme with a cofactor whereas holoenzyme describes the whole enzyme including the cofactor.
What are the six classes of enzymes and what do they do?
Oxidoreductases transfer electrons.
Transferases transfer groups.
Hydrolases catalyse hydrolysis.
Lyases form or add groups to double bonds.
Isomerases transfer groups within molecules to form isomers.
Ligases work with ATP to form different carbon bonds.
What will happen to enthalpy and entropy values during a spontaneous reaction?
Enthalpy will decrease and entropy will decrease. The delta G value must be negative.
What is the free Energy equation?
^G=^H-T^S
What is the transition state and energy barrier?
The transition state is when chemical bonds within the substrate are broken and formed.
The energy barrier is the energy required to make the reaction happen such as positioning the groups right and bond arrangement.
Name and describe three ways that enzymes reduce the activation energy
Reducing the entropy means that the enzyme lines up the substrates into the correct orientation for collision to result in a reaction.
Desolvation means that the enzyme forms bonds with the substrate that replace hydrogen bonds in solution.
Induced fit results in conformational changes to the protein.
What is the Michaelis Menten equation and what is the RDS?
E + S <> ES > E + P
The second step is slower so is the RDS.
What does the M-M equation look like at high and low substrate concentrations?
Low
V0=Vmax[S]/Km
High
V0=Vmax
What is Km?
Km is equivalent to the substrate concentration when the initial reaction rate is at half of Vmax.
What does Km tell?
It tells you how stable the ES complex is so a larger value means a less stable complex and vice versa. It also gives you a clue to the affinity of the enzyme with its substrate.
What does Vmax tell you?
It shows how fast an enzyme works.
What are the Vmax and Km for gluco and hexokinase?
Glucokinase has a high Km and high Vmax for glucose and hexokinase is the opposite.
When there are more than one substrate what are the three ways transfers can work?
Random order with ternary complex
Ordered with ternary complex
No ternary complex formed
