411: Exam 1

Question 1

hexokinase activators and inhibitors

Answer 1

activators: insulin, AMP
inhibitors: G6P, ATP

Question 2

phosphofructokinase activators and inhibitors

Answer 2

activators: AMP, ADP, G6P, F2,6BP
inhibitors: citrate, ATP

Question 3

enolase inhibitor

Answer 3

fluorophosphates (FPO32-)

Question 4

pyruvate kinase inhibitors and activators

Answer 4

inhibitors: alanine, citrate, acetyl coA, ATP, cAMP-dependent phosphorylation
activators: F1,6BP, AMP

Question 5

what sugars do hexokinase and glucokinase break down?

Answer 5

hexokinase: glucose, fructose, mannose
glucokinase: glucose only

Question 6

difference in capacity and Km between hexokinase and glucokinase

Answer 6

hexokinase: low capacity (slow chem step) and low Km (efficient binding to phosphorylate glucose)
glucokinase: high capacity (fast chem), high Km (different regulatory mechanism

Question 7

isozymes

Answer 7

• catalyze same rxn but are tissue specific
• allows for different form of regulations

ask emma about this

Question 8

similarities between hexokinase and glucokinase

Answer 8

• both make G6P
• prevent ATP from reacting with water by causing conformational change once glucose binds (otherwise water will hydrolyze ATP)

Question 9

what does a reversible reaction say about energy?

Answer 9

low free energy in reaction

Question 10

what does phosphoglucoisomerase do?

Answer 10

• primes C3 and C4 for later aldolytic cleavage
• mechanism: acid-catalyzed ring opening and base-catalyzed ring closinig
• cis-endeiolate intermediate

Question 11

what does fructose-2-6-biphosphate do?

Answer 11

increases the affinity of phosphofructokinase for F6P

Question 12

Class 1 aldolase

Answer 12

• found in animals
• formation of a covalent Schiff Base E-S intermediate

Question 13

triose phosphate isomerase

Answer 13

• enediol intermediate
• acid/base catalysis
• Glu: base His: acid
• near perfect enzyme Kcat/Km (R-> P)

Question 14

what does a dehydrogenase enzyme indicate?

Answer 14

electron carrier in the reaction

Question 15

Glyceraldehyde-3-phosphate dehydrogenase

Answer 15

• gives 2e- as a hydride
• covalent catalysis (covalent bond between E & S)

Question 16

what kind of mechanism does enolase do?

Answer 16

dehydration reaction

NOT redox

Question 17

how does NADH transfer electrons?

Answer 17

• H:
• 2e- and a proton

Question 18

purpose of lactate dehydrogenase

Answer 18

regenerate NAD+ so glycolysis can continue

Question 19

what happens when lactate gets ionized?

Answer 19

release H+ –> decrease pH –> hemoglobin T state (Bohr effect)

lactate –> lactic acid

Question 20

liver recylces lactic acid to _______

Answer 20

glucose

Question 21

slow-twitch vs fast twist muscles

Answer 21

slow: aerobic conditions (endurance,
fast: anaerobic conditions

Question 22

what is biotin?

Answer 22

a carbon carrier used by pyruvate carboxylase

Question 23

why does cell add CO2 with pyruvate carboxylase and then take it back off with PEPCK?

Answer 23

decarboxylation drives the formation of the enol that GTP phosphorylates

Question 24

what does glucagon signal?

Answer 24

low blood glucose (want GNG on)

Question 25

what does glucose-6-phosphatase do and where?

Answer 25

• convert G6P to glucose in ER
• liver and kidney