5.9 cofactors

Question 1

what are cofactors

Answer 1

small molecules in which catalytic activity of many enzymes depend on its presence

Question 2

two groups of cofactors

Answer 2

essential ions and small organic molecules called coenzymes

Question 3

what are apoenzymes

Answer 3

polypeptides with no coenzymes. non functional

Question 4

what are holo enzymes

Answer 4

apoenzymes + cofactors

Question 5

coenzyme sare grouped into

Answer 5

cosubstrates (loosely bound) and prosthetic group (tightly bound)

Question 6

what are prosthetic groups

Answer 6

remains bound to enzyme during course of rxn, can be covalently linked to apoenzyme, or tightly bound to active site by weak interaxns

Question 7

what are cosubstrates

Answer 7

subtrates in enzyme catalyzed rxns, altered in the course of rxn and dissociates from active sitre, original structure is regenerated in subsequent rxn by another enzyme

Question 8

how are cosubstrated different than other sbstrates

Answer 8

is repeatedly recycled w/in cell, other substrates have products that undergo further transformation

Question 9

fn of cosubstrate

Answer 9

shuttle mobile metabolic groups among different enzyme-catalyzed rxn

Question 10

example of a cosubstrate

Answer 10

NAD+ are cosubstrates of pyruvate dehydrogenase

Question 11

essential ions are gropued into

Answer 11

activator ions (loosely bound) and metal ions of metalloenzymes (tightly bound)

Question 12

what are metalloenzymes

Answer 12

metals, whether tightly bound to enzyme or taken up from sln along w/substrate, can participate in catalysis

Question 13

fn of metals

Answer 13

mediate re-ox rxn by reversible changes in metal ion;s oxidation state, inon interzxn btwn enzyme bound mwtal and substrate can orient substrate for rxn or stabalize a charged rxn transition state

Question 14

examples of metal ions that play a structural role

Answer 14

Na+, K+, Ca2+

Question 15

examples of metal ions that play a strucutral or catalytic role

Answer 15

mg2+ or zn2+