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unit 6: MCP > regulation of glycolysis/gluc. (8) > Flashcards

regulation of glycolysis/gluc. (8) Flashcards

1
Q

what are the 3 glycolytic steps that are considered rate limiting?

A
  1. hexokinase
  2. prohophofructokinase
  3. pyruvate kinase
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2
Q

what does it mean if an enzyme catalyzes a rxn that is highly exergonic

A

it means that its rate of catalysis limits flux through that step in the pathway

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3
Q

what does it mean if an enzyme catalyzes a rxn that is near equilibrium?

A

it means that its rate of catalysis is much faster than net flux through that step

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4
Q

which points in glycolysis/gluconeogensis are the control points for regulating flux?

A

the bypass points

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5
Q

what isn’t bypass III a good point for regulation of glycolysis?

A

because G6P is required for other pathways

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6
Q

why is pyruvate kinase a good point for regulation?

A

because it needs to be turned off during gluconeogensis because other concentration of its substrate- PEP will be elevated

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7
Q

what allosterically inhibits PFK?

A

ATP as a feedback inhibitor

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8
Q

what is the affect of AMP on glycolysis?

A

it speeds up glycolysis to replenish the ATP supply

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9
Q

why occurs when an allosteric activator binds to PFK?

A

it assumes a conformation that places a stabilizing position charge (R162) near the negatively charged substrate

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10
Q

what occurs when an allosteric inhibitor binds to PFK?

A

the conformation assumed places a destabilizing negative charge (E161) near the negatively charged substrate

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11
Q

besides AMP, what other molecule competes with ATP for binding to the PFK allosteric site?

A

F2,6BP

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12
Q

what is the effect of F26BP and AMP on gluconeogenesis?

A

it slows gluconeogenesis when glycolysis is active

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13
Q

in the dephosphorylated state that catalytic site in which domain is active?

A

the PFK-2 kinase domain is active

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14
Q

in the phosphorylated state that catalytic site in which domain is active?

A

FBPase-2 phosphatase domain is active

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15
Q

what substrate activates pyruvate kinase? inhibits it?

A

FBP activates pyruvate kinase

acetyl-coA and ATP are feedback inhibitors. also inhibited by phosphorylation induced by glucagon

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16
Q

what activates pryuvate carboxylase?

A

acetyl coA

17
Q

what are the effects of glucagon on glycolytic enzymes?

A

decreases their levels

18
Q

what are the effects of glucagon on PEPCK, FPBase and G6Pase?

A

increases their level

19
Q

which enzyme does insulin cause a decrease of?

A

PEPCK

20
Q

list the 3 ways that reciprocal regulation of glycolysis and gluconeogenesis is accomplished

A
  1. Allosteric ligands: ATP, ADP, AMP, F26BP, FBP and acetyl CoA
  2. Protein kinase/phosphatase directly on pryuvate kinase and indirectly through F26BP
  3. Hormonal regulation of gene expression (insulin, glucagon)
21
Q

which enzyme is shared by both the synthesis and breakdown pathway?

A

phosphoglucomutase

22
Q

is there a glucagon receptor in the liver? in the muscle?

A

only in the liver

23
Q

how does insulin increase glucose uptake in muscle and adipocytes?

A

by increases the number of glucose transporters at the cell surface

24
Q

when blood sugar increases, insulin dephosphorylates what? (5)

A
  • PFK2 (kinase active, increase F2,6BP)
  • Pyruvate kinase (active)
  • Pyruvate dehydrogenase (E1 active)
  • Glycogen synthase (active)
  • Glycogen phosphorylase (inactive)
25
Q

what pathawys are activated by insulin?

A

glycolysis, CAC and glycogenesis

26
Q

when blood sugar decreases and glucagon is released, what does it phosphorylate? (5)

A 
o	PFK2 (phosphatase active, decrease F2,6,BP)
o	Pyruvate kinase (inactive)
o	Pyruvate dehydrogenase (E1 inactive)
o	Glycogen synthase (inactive)
o	Glycogen phosphorylase (active)
27
Q

glucagon activates which pathways? (2)

A

gluconeogensis & glycogenolysis

28
Q

What are three examples of product inhibition in CAC regulation?

A
  1. citrate synthase by citrate
  2. isocitrate dehydrogenase by NADH
  3. a-ketoglutarate dehydrogenase by NADH & succ coA
29
Q

What is an example of feedback inhibition in the CAC?

A

citrate synthase is inhibited by succ coA

30
Q

What is an example of allosteric inhibition in the CAC?

A

isocitrate dehydrogenase is:

  • activated by ADP
  • inhibited by ATP

unit 6: MCP (17 decks)

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