2.1 Enzyme energetics and kinetics basics

Question 1

Define kinetics

Answer 1

Kinetics - field of chemistry concerned with measuring and studying reaction rates

Question 2

Define energetics

Answer 2

Energetics - branch of science which deals with properties of E and how it is distributed in physical / chemical / biological processes

Question 3

How do enzymes change reaction kinetics?

Answer 3

Enzymes change kinetics by acting as catalysts and accelerating reactions

Question 4

Why are enzymes effective drug targets?

Answer 4

Enzymes control majority bio pathways in organisms - drugs can be used as enzyme inhibitors to stop reactions

Question 5

What advantages do enzymes have in biocatalysis?

Answer 5

• more sustainbale - can be reused
• stereoselective (more specific)

Question 6

What are the enzyme classes?

Answer 6

LIL OTH

Question 7

What are the different enzyme functions in catalysis?

Answer 7

1) provide reaction surface
2) bring reactants together - decrease distance
3) align at needed orientation
4) weaken bonds for easier breaking (stabilises intermediates)
5) provide acids / bases for the recation
6) provide nucleophiles

Question 8

What is the general enzymatic cycle?

Answer 8

1) Substrate enters
2) Substrate - enzyme complex formed
3) Active site binding
4) Substrate converted to product
5) Product released from enzyme
6) Enzyme ready to be reused

Question 9

What are the two enzyme reactions models / mechanisms?

Answer 9

• key-lock model (very specific: rigid active site and substrate)
• induced fit model (active sites change confirmation depending on substrate)

Question 10

What are the binding interactions in substrate-enzyme complex?

Answer 10

Multiple weak interactions:
- H-bonds
- ionic interactions (salt bridges)
- hydrophobic effect
- van der Waal’s

Question 11

Explain proximity effect

Answer 11

XX

Question 12

Explain orientation effect

Answer 12

XX

Question 13

What are the catalytic mechanisms performed by enzymes?

Answer 13

• **covalent catalysis **-> nucleophilic catalysis: covalent bond formed between enzyme and 1/more substartes (R groups at active sites serve as Nuc)
• acid/base catalysis: H+ transfer (R at active site accepts/donates H+)
• electrostatic catalysis: enzyme stabilises transition state
• approximation catalysis: binds to mutiple substrates - positions favourably for reaction (binding reduces rotational entropy)
• cofactor catalysis (metal / coenzyme): cofactors loosely bind to enzymes - activate enzymes
  CAEAC

Question 14

Gibbs free E equation and spotaneous reactions

Answer 14

ΔG = ΔH - TΔS
ΔG < 0 - reaction spontaneous

Question 15

How do enzymes turn unfavourable reactions into favourable?

Answer 15

Enzymes couple unfavourable (endergonic) reactions (ΔG > 0) with favourable (exergonic) (ΔG < 0) => overall ΔG must be < 0