Enzymes

Question 1

What is an enzyme

Answer 1

1. Protein
2. Polypeptide chain is folded to form a 3D structure
3. Amino acids from the enzyme and metal ions at the active site interact with specific parts of the substrate to bind it in a specific orientation

Question 2

Reactions and rates

Answer 2

Irreversible A-B 1st order
d[a]/dt = d[b]/dt =k[a]
Irreversible A+B-C 2nd order
-d[a]/dt = -d[b]/dt =d[c]/dt =k[a][b]
Reversible A-B 
-d[a]/dt = d[b]/dt = kf[A] - kr[B]

Question 3

Reaction thermodynamics

Answer 3

If ∆G for a reaction is negative, the reaction will occur spontaneously
The size of ∆G does not affect how fast the reaction occurs
∴The larger ∆G‡, the smaller the rate constant for the reaction.

Question 4

Catalysts

Answer 4

Catalysts reduce the size of the activation energy barrier
Catalysts do not affect ∆G for a reaction
Since catalysts reduce ∆G‡ they increase the rate constants for the forward AND reverse reactions
Enzymes are protein catalysts that are usually much more efficient than chemical catalysts at physiological temperatures and pressures.

Catalytic Power = Rate constant of catalysed reaction/ Rate constant of uncatalysed reaction