final exam

Question 1

What are the 5 major mechanisms of enzyme control?

Answer 1

Covalent changes, conformational/allosteric changes, product inhibition, substrate/cofactor availability, regulatory macromolecules.

Question 2

Is zymogen activation reversible or irreversible?

Answer 2

Irreversible proteolytic cleavage.

Question 3

Example of zymogen activation?

Answer 3

Trypsinogen → Trypsin.

Question 4

Phosphorylation is what type of modification?

Answer 4

Reversible covalent modification.

Question 5

Which enzyme catalyzes phosphorylation?

Answer 5

Kinases.

Question 6

Allosteric regulation definition?

Answer 6

Effector binds to non-active site causing conformational change.

Question 7

Effect of allosteric activator?

Answer 7

Increases enzyme affinity for substrate.

Question 8

Effect of allosteric inhibitor?

Answer 8

Decreases substrate binding at catalytic site.

Question 9

Curve shape of allosteric enzyme?

Answer 9

Sigmoidal.

Question 10

Feedback inhibition definition?

Answer 10

Product inhibits early enzyme in pathway.

Question 11

Competitive inhibition effect on Km?

Answer 11

Km increases.

Question 12

Competitive inhibition effect on Vmax?

Answer 12

Vmax unchanged.

Question 13

Where do competitive inhibitors bind?

Answer 13

Active site.

Question 14

How to overcome competitive inhibitor?

Answer 14

Increase substrate concentration.

Question 15

Noncompetitive inhibition effect on Km?

Answer 15

Km unchanged.

Question 16

Noncompetitive inhibition effect on Vmax?

Answer 16

Vmax decreases.

Question 17

Where do noncompetitive inhibitors bind?

Answer 17

Allosteric/regulatory site.

Question 18

Definition of suicide inhibitor?

Answer 18

Processed by enzyme then irreversibly inactivates it.

Question 19

Example of suicide inhibitor?

Answer 19

Aspirin.

Question 20

Transition-state analog binds with what affinity?

Answer 20

Very high affinity.

Question 21

Unspecific inhibition occurs when?

Answer 21

Non-physiological conditions like pH, heat, detergents.

Question 22

Example of product inhibition?

Answer 22

G6P inhibiting hexokinase.

Question 23

Intrinsic control definition?

Answer 23

Metabolite-based regulation.

Question 24

Extrinsic control definition?

Answer 24

Hormone-based regulation.

Question 25

Positive effector example?

Answer 25

ADP activates PFK-1.

Question 26

Negative effector example?

Answer 26

ATP inhibits PFK-1.

Question 27

Bacterial RNA polymerase core composition?

Answer 27

α2 β β' ω (5 subunits).

Question 28

What forms the RNA polymerase holoenzyme?

Answer 28

Core enzyme + sigma factor.

Question 29

Function of sigma factor?

Answer 29

Promoter recognition and initiation.

Question 30

RNA Pol I function?

Answer 30

Transcribes rRNA except 5S.

Question 31

RNA Pol II function?

Answer 31

Transcribes mRNA.

Question 32

RNA Pol III function?

Answer 32

Transcribes tRNA + 5S rRNA.

Question 33

CTD phosphorylation allows what?

Answer 33

RNA Pol II elongation.

Question 34

Why multienzyme complexes?

Answer 34

Increase speed, protect intermediates, increase efficiency.

Question 35

PDC components?

Answer 35

E1 decarboxylase, E2 transacetylase, E3 dehydrogenase.

Question 36

PDC reaction?

Answer 36

Pyruvate + CoA + NAD+ → Acetyl-CoA + NADH + CO2.

Question 37

PDC location?

Answer 37

Mitochondrial matrix.

Question 38

Fatty acid synthase structure?

Answer 38

Dimer with 7 catalytic sites.

Question 39

In vitro assay system type?

Answer 39

Closed system.

Question 40

In vivo assay system type?

Answer 40

Open system.

Question 41

First pellet in centrifugation?

Answer 41

Nuclei.

Question 42

High-speed pellet contains?

Answer 42

Ribosomes/microsomes.

Question 43

Mitochondrial marker enzyme?

Answer 43

Succinate dehydrogenase.

Question 44

Nuclear marker enzyme?

Answer 44

DNA polymerase.

Question 45

Lysosomal marker enzyme?

Answer 45

Acid hydrolases.

Question 46

Enzyme turnover definition?

Answer 46

Continuous replacement of enzymes.

Question 47

Turnover equation?

Answer 47

d[E]/dt = Ks − Kd[E].

Question 48

How to measure Ks?

Answer 48

Pulse/infusion radioactive amino acids.

Question 49

How to measure Kd?

Answer 49

Chase decay of labeled enzyme.

Question 50

Enzyme half-life definition?

Answer 50

Time for enzyme quantity to reach 50%.

Question 51

PEST sequences mean what?

Answer 51

Rapid degradation.

Question 52

Noncompetitive inhibitors effect?

Answer 52

Decrease Vmax.

Question 53

Km at half Vmax represents what?

Answer 53

Michaelis constant.

Question 54

Zymogens require what to activate?

Answer 54

Irreversible proteolytic cleavage.

Question 55

Hexokinase regulation type?

Answer 55

Feedback inhibition by G6P.

Question 56

Glycolysis location?

Answer 56

Cytosol.

Question 57

Pyruvate dehydrogenase function?

Answer 57

Converts pyruvate → acetyl-CoA.

Question 58

Fatty acid synthase location?

Answer 58

Cytosol.