Regulation of Carbohydrate Metabolism Flashcards by brittany gouse

When blood sugar increases:
Insulin is ____

released

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Insulin is released, which leads to the
dephosphorylation of:

PFK-2
Pyruvate kinase
Pyruvate dehydrogenase
Glycogen synthase
Glycogen phosphorylase

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When blood sugar decreases: ____ is released

Glucagon

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glucagon release leads to the ______

•PFK-2 (phosphatase active, ↓ F2,6BP)

Pyruvate kinase (inactive)

•Pyruvate dehydrogenase (E1 inactive)

Glycogen synthase (inactive) •Glycogen phosphorylase (active)

phosphorylation

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Insulin is released, which leads to the
dephosphorylation of:
PFK-2, Pyruvate kinase, Pyruvate dehydrogenase, Glycogen synthase, Glycogen phosphorylase

leads to active

Glycolysis
CAC
Glycogen synthesis (Glycogenesis)

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When blood sugar decreases: Glucagon is released, which leads to the phosphorylation of:PFK-2, Pyruvate kinase, Pyruvate dehydrogenase, Glycogen synthase, Glycogen phosphorylase

this leads to active

Gluconeogenesis

Glycogen breakdown (Glycogenolysis)

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enzymes that operate ____equilibrium may be so efficient that a reduction in their activity will have little or no effect on the overall flux.

near

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when a reaction is rate limiting

[S] ____ [S]eq

[S] > [S]eq

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when rxn is rate limiting

[P] ___ [P]eq

[P] < [P]eq

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when rxn is rate limiting

∴ΔG = ___

negative

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___ (3) catalyze glycolytic steps that are rate limiting

Hexokinase, Phosphofructokinase, and Pyruvate Kinase

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When an enzyme catalyzes a reaction that is near equilibrium, it means that its rate of catalysis is

much faster than net flux through that step

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When an enzyme catalyzes a reaction that is ____, it means that its rate of catalysis limits flux through that step in a pathway

highly exergonic

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what steps need to be bypassed (bc they are highly exergonic) in glucogenogensis?

the same ones that are rate limiting in glycolysis

Hexokinase, Phosphofructokinase, and Pyruvate Kinase

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which point is not the optimal point to regualte glycolysis? why?

Bypass III is not the optimal point to regulate Glycolysis because G6P is required for other pathways

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which point IS a good point to regulate glycolysis?

PFK

or pyvutate kinase

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why does pyruvate kinase need to be turned off during glucogenogenssi?

the concentration of its substrate, PEP, will be elevated

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PFK is allosterically inhibited by

ATP as a feedback inhibitor

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___ effectively competes with ATP for binding at the allosteric site

AMP
F2,6BP

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what speeds up glyciolysis? why?

AMP effectively competes with ATP for binding at the allosteric site signaling
Glycolysis to speed up to replenish the ATP supply

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When an allosteric activator binds, PFK assumes a conformation that places a ___ near a ____

stabilizing positive charge (R162) near the negatively charged substrate

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when an allosteric inhibitor binds to PFK, the conformation assumed places a

destabilizing negative charge (E161) near the negatively charged substrate

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F2,6BP prevents ____ because it competes with ATP for binding on PFK

feedback inhbiition of glyolysis

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, F2,6BP and AMP bind to an allosteric site on ____and inhibit, thereby slowing Gluconeogenesis

FBPase

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effect of F2,6BP and AMP on gluyconeogensis?

slow gluconeogensis

difference between FBP and F2,6BP structurally?

The second phosphoryl on F2,6BP is on the C2 hydroxyl instead of on the C1 hydroxyl as is the case for FBP

In the dephosphorylated state, the catalytic site in the ____ domain ss active

kinase domain, called PFK-2

what is PFK-2?

catalytic site in the kinase domain

In the phosphorylated state, the catalytic site in the ____ domain is active

phosphatase domain, FBPase-2

increased CAMP

increased enzyme phoshporylation

activation of FBP-ase-2 and inactivation of PFK-2

dec F26P

1. inhibition of PFK 2. activation of FBPase

increased glucogenosesis

blood Glu concentration is high, insulin promotes decreased enzyme phosphorylation resulting in increased \_\_\_

F2,6P ---\> inc glycolysis, dec gluconeogesnsis

Hormonal regulation of \_\_\_in response to blood [Glu] allows selective activation of the pathway needed, while turning off the pathway not needed

[F2,6BP]

Pyruvate Kinase is activated by

FBP

Pyruvate Kinase is also inhibited by

1. phosphorylation induced by Glucagon 2. acetyl coa 3. atp

Pyruvate Carboxylase is activated by \_\_\_\_

Acetyl-CoA

Glucagon causes a decrease in the level of

Glucokinase & PFK (Glycolytic enzymes)

Glucagon causes an increase in the level

PEPCK, FBPase, and G6Pase ( Gluconeogenic enzymes)

Insulin causes a decrease in the level of the

PEPCK (Gluconeogenic enzyme)

The synthesis/breakdown pathways of glycogen can be thought of as one big bypass. Only ____ is shared

phosphoglucomutase

In the pathway leading to glycogen, \_\_\_\_is the enzyme regulated

glycogen synthase

In the pathway that breaks down glycogen, \_\_\_\_is the enzyme regulated

glycogen phosphorylase

An increase in cAMP activates Protein Kinase A which activates Phosphorylase Kinase, which activates \_\_\_\_

Glycogen Phosphorylase

Active **PKA** nd **Phosphorylase Kinase** inhbiit

Glycogen Synthase

Protein Kinase A inactivates

Phosphoprotein Phosphatase-1

Insulin activates\_\_\_\_ and reverses all of the changes caused by an active Protein Kinase A

Phosphoprotein Phosphatase-1

Glucagon binds to a liver cell receptor which produces

cAMP --\> glycogen breakdown --\> release of Glucose to blood stream

\_\_\_ and \_\_\_binds to a liver cell receptor which produces cAMP --\> glycogen breakdown --\> release of Glucose to blood stream

Epinephrine and Glucagon

Muscle cells have no ____ receptor

Glucagon receptor they are not responsible for maintaining blood glucose

However, muscle cells still need to respond to ____ to increase availability of Glu-6-P for ATP production

epinephrine

Insulin increases ___ in muscle

increases number of glucose transporters ---\> inc Glu uptake

inc glucose uptake in muscle leads to

inc glycogen sythnesis

inc adipocytes uptake in muscle leads to

increased synthesis of triacylglycerols

When blood Glu is low, Phosphorylase will be in the ____ and \_\_\_

Phosphorylated form and in the active r confirmation

When blood Glu is high, ATP and G6P will be high and dephosphorylated Phosphorylase will be in the ____ confirmation

inactive T conformation

what are E4 and E5?

Pyruvate Dehydrogenase Complex

the Pyruvate Dehydrogenase Complex kinase is activated by

NADH and Acetyl-CoA to phosphorylate and inactivate E1

\_\_\_ and ____ inhibit the Kinase of the Pyruvate Dehydrogenase Complex

pyruvate and ADP

Pyruvate Dehydrogenase Complex The Phosphatase is activated by\_\_\_\_to convert E1 back to the active form

calcium ion

Pyruvate Dehydrogenase Complex product inhibition of e3 occurs by

nadh

Pyruvate Dehydrogenase Complex E2 is inhibited by

Acetyl-CoA

what inhbiits cit synthease?

citrate Succ-CoA

what inhibits isocitrate dehydrogenase?

NADH ATP

what inhbiits α-ketoglutarate DHase

NADH and Succ-CoA

what activates isocitrate dehydrogenase?

ADP