Enzymes and Kinetics

Question 1

What is the slowest step in an enzyme catalyzed reaction?

Answer 1

Ligand binding step

Question 2

Coenzyme

Answer 2

organic molecules that associate with or bind to enzyme (e.g. vitamins)

Question 3

Transferase

Answer 3

transfers functional groups from one SUBSTRATE to another

Question 4

Kinase

Answer 4

covalently attaches phosphates from ATP

Question 5

Phosphatase

Answer 5

removes phosphate groups

Question 6

Dehydrogenase

Answer 6

removes hydrogen or hydride usually transfers to NAD or FAD

Question 7

Isomerase

Answer 7

converts substrate to another isomer (D to L, cis to trans, move functional group

Question 8

Protease

Answer 8

cleaves peptide bond

Question 9

Isoform

Answer 9

differs in amino acid sequence but performs similar function with slightly different properties (e.g. fetal hemoglobin vs. adult hemoglobin)

Question 10

Isozyme

Answer 10

same as isoform but with an enzyme

Question 11

1 international unit (IU)

Answer 11

enzyme that catalyzes 1umol substrate per min under specified pH, temp, [subst]

Question 12

T or F : most isozymes have completely different genes encoding for them.

Answer 12

T

Question 13

Characteristics of ideal drugs

Answer 13

Highly specific, non-metabolizable, elimated in urine and slowly

Question 14

Receptors with enzyme activity have:

Answer 14

substrate binding site(s), active site, ligand binding site

Question 15

most common mechanism of enzyme regulation

Answer 15

allostery

Question 16

most common point for pathway regulation

Answer 16

branches and start point

Question 17

What is proteolysis an example of?

Answer 17

A post-translational modification

Question 18

What effects can pH change have on a protein?

Answer 18

conformation, solubility, transport of the compound

Question 19

major buffer in urine

Answer 19

phosphate

Question 20

henderson hasselbach eqn.

Answer 20

pH = pKa + log ( [A-]/[HA] )

Question 21

common ions used for charge balance on proteins

Answer 21

K+, Cl-, phosphate

Question 22

Mechanisms to help in protein folding

Answer 22

molecular chaperones

Question 23

scatchard eqn.

Answer 23

r/[A] = n/kd - r/kd

Question 24

r in scatchard eqn.

Answer 24

r = [A]/ (kd + [A])

Question 25

Slowest step in enzymatic reaction?

Answer 25

substrate binding step

Question 26

Why is substrate binding the slowest step in an enzymatic reaction?

Answer 26

dissociation is rapid and probability of substrate encountering the active site is low.

Question 27

hallmarks of competitive inhibition

Answer 27

Higher km, same Vmax

Question 28

hallmarks of noncompetitive inhibition

Answer 28

same km, Lower Vmax

Question 29

What is the effect of an allosteric activator? on the langmuir isotherm?

Answer 29

Stabilizes R state, lowers km, makes curve steeper

Question 30

What is the effect of an allosteric inhibitor? on the langmuir isotherm?

Answer 30

Stabilizes T state, raises km, moves curve right, can be overcome

Question 31

Do allosteric activators/inhibitors have greater effects at low or high substrate conc.?

Answer 31

low

Question 32

Where are rate limiting enzymes found in enzymatic pathways?

Answer 32

start points and branch points

Question 33

What is r in the scatchard eqn?

Answer 33

The average number of ligand bound per protein