Other Flashcards
What are the Six classes of enzyme-catalysed reaction?
Isomerisation Group transfer Ligation requiring ATP hydrolysis Functional group addition or removal Oxidation-reduction Hydrolytic
What is the definition of an activated carrier?
A small molecule that carries a chemical group via a high energy bond. Transfer of the group requires hydrolysis of the bond and release of energy.
What is another name for activated carrier?
cofactor
Give 4 examples of activated carriers and what chemical group they “carry”
ATP = activated carrier of phosphoryl group via phosphoanhydride bond
NADH = activated carrier of high energy electrons within nicotinamide ring
FADH2 = activated carrier of high energy electrons within isoalloxazine ring
Acetyl CoA = activated carrier of acetyl group via thioester bond
Electrons move from a ______ redox potential to a more ______ redox potential. Why?
negative
positive
Because the more positive redox potential has higher affinity for electrons so are readily reduced
Are activated carriers kinetically unstable or stable? why?
They are kinetically stable because they have a high activation energy meaning they require the action of an enzyme for the reaction to occur. This allows for the control of free energy or electron transfer
Are activated carriers thermodynamically unstable or stable? why?
They are thermodynamically unstable because when the high energy bond is hydrolysed this releases energy. i.e they are exergonic
What are the 4 main ways an enzyme lowers the activation energy of a reaction?
1) induced fit - enzymes distort their substrates towards the transition state
2) Enzyme binding of substrates results in a reduction in the degrees of freedom of movement/rotation – constrains highly dynamic substrates, which stores energy
3) The multiple weak binding interactions between the substrate and specific residues in the active site contribute bonding energy towards the activation energy
4) Provide alternative reaction pathways (individual amino acids participate within the catalytic mechanism itself – E.g. His195 of lactate dehydrogenase plays direct role in wave of electrons, E.g. Ser in chymotrypsin)
What is the transition state?
The point at which the reaction can happen equally well in either direction
What is the difference between a co-enzyme and a cofactor?
Cofactors are non-protein components
Co-enzymes are organic cofactors
What is the name for a tightly associated cofactor? give an example
prosthetic group
E.g. FAD in pyruvate dehydrogenase
What is the name for a loosely associated bound cofactor? give an example
co-substrate
E.g. NAD+ and NADP+
What is the water-soluble vitamin from which NAD+/NADP+ are derived?
Niacin
What is the water-soluble vitamin from which FMN/FAD are derived?
riboflavin
What is the water-soluble vitamin from which CoA is derived?
pantothenic acid
