Lecture 10

Question 1

General acid-base catalysis

Answer 1

catalysis involving proton transfers to or from a molecule other than water

Question 2

Specific acid-base catalysis

Answer 2

acid or base catalysis involving the constituents of water (hydroxide or hydronium ions

Question 3

cofactor

Answer 3

inorganic ion or coenzyme required for enzyme activity

Question 4

General role of NAD

Answer 4

Hydride (H-) ion transfers

Question 5

General role of pyridoxal phosphate (B6)

Answer 5

Transfer of amino groups and amines

Question 6

covalent catalysis and the circumstances where it arises

Answer 6

works only if new reaction path has lower net activation energy than usual path

formation of covalent complex requires nucleophilic attack

catalyst must be linked to substrate transiently

conditions

1. catalyst must be better nucleophile than acyl acceptor (H2O)
2. Intermediate must be more reactive than substrate
3. Intermediate must be less stable than product

Question 7

importance of carbonyls

Answer 7

Split C-C bond if next to next to carbonyl carbon (resonance stabilized)

Question 8

prosthetic group vs cofactor

Answer 8

prosthetic group is just tightly bound cofactor.

cofactor is group bound to enzyme that gives it a little different chemistry

Question 9

metal ion catalysis

Answer 9

metals bind to substrate to orient them

mediate redox reactioins by reversible changes in metal oxidation states

electrostatic shielding or stabilization of negative charges during reaction