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Term I: Cell Biology > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

What is gain of electrons called?

A

Reduction

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2
Q

What is loss of electrons called?

A

Oxidation

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3
Q

What bonds in ATP provide cellular energy?

A

High-energy phosphate bonds between 2nd and 3rd phosphates only (not bond between phosphate and sugar!)

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4
Q

Where does glycolysis take place?

A

Cytoplasm

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5
Q

What is standard free energy?

A

ΔGo - the free energy that is released when reactants are at a standard state concentration (1M) and are allowed to come to equilibrium

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6
Q

What will happen in a reaction if ΔG < 0?

A

Reaction will proceed forward

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7
Q

What will happen in a reaction if ΔG > 0?

A

Reaction will go backwards

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8
Q

What will happen in a reaction if ΔG = 0?

A

Reaction will stay at equilibrium - no change

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9
Q

D-Glucose –> Glucose 6-phosphate
(Step 1)

What enzyme? What is significant? Significant products?

A

Glucokinase - in liver and pancreas
Hexokinase - in muscle

Exergonic reaction - highly favorable, regulated step

Lose ONE ATP

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10
Q

Glucose 6-phosphate –> Fructose 6-phosphate
(Step 2)

What enzyme? What is significant? Significant products?

A

Phosphoglucose Isomerase

Isomerization - very little change

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11
Q

Fructose 6-phosphate –> Fructose 1,6-biphosphate (Step 3)

What enzyme? What is significant? Significant products?

A

PFK - phosphofructose kinase

Highly regulated by metabolites/hormones

Lose ONE ATP

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12
Q

What kinds of signals inhibit PFK?

A

ATP-like signals (like citrate)

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13
Q

What kinds of signals stimulate PFK?

A

AMP-like signals (like fructose 2,6-bisphosphate or F2,6-BP)

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14
Q

Fructose 1,6-biphosphate –> Dihydroxyacetone phosphate –> Glyceraldehyde 3-phosphate
(Step 4)

What enzyme? What is significant? Significant products?

A

Fructose bisphosphate aldolase and Triosephosphate isomerase

Isomerization step - little change

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15
Q

Glyceraldehyde 3-phosphate –> 1,3-bisphosphoglycerate
(Step 5)

What enzyme? What is significant? Significant products?

A

(GAPDH) Glyceraldehyde phosphate dehydrogenase

Creates high-energy phosphate bond by replacing high-energy thioester bond and using Mg2+ cofactor

Creates TWO NADH

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16
Q

1,3-bisphosphoglycerate –> 3-phosphoglycerate
(Step 6)

What enzyme? What is significant? Significant products?

A

PGK (3-phosphoglycerate kinase)

Uses Mg2+ cofactor

Creates TWO ATP

17
Q 
Phosphoenol pyruvate (PEP) --> Pyruvate
(last step)

What enzyme? What is significant? Significant products?

A

Pyruvate Kinase

Last, irreversible step of glycolysis

Creates TWO ATP

18
Q

What are the functions of skeletal muscle?

A

Provide normal mvt, respond to stress w/ continued work output, adapt to short periods of anaerobic work

19
Q

What is skeletal muscle’s metabolic role?

A

Generate ATP to drive muscle contraction, store food locally for immediate need, take metabolic precursors from other organs, serve as storage site for proteins

20
Q

What is function of liver?

A

Regulates blood glucose, (absorbs excess glucose in fed state, makes glucose during fasted state), Responds metabolically to higher level hormonal control

21
Q

What is liver’s metabolic role?

A

Store glucose as glycogen, convert excess energy to fat, convert and break down metabolites

22
Q

What are the stimulatory and inhibitory signals in energy generation?

A

Stimulatory - low-energy AMP- like signals

Inhibitory - high-energy, ATP-like signals

23
Q

What are the stimulatory and inhibitory signals in food storage?

A

Activators - ATP-like

Inhibitors - AMP-like

24
Q

High levels of what molecule indicate that glycolysis is backed up? Why?

A

Glucose 6-phosphate - this molecule normally serves as feedback inhibition for hexokinase or glucokinase

25
Q

What does hexokinase’s low Km say about its function?

A

It will be saturated at normal glucose levels in blood so muscles can get glucose regularly

26
Q

What does glucokinase’s high Km say about its function?

A

Since it is in the liver, its job is to ensure blood glucose levels are regulated properly, thus it will only be saturated when blood glucose levels are very high

27
Q

Describe hormonal regulation of PFK in liver.

A

1) High insulin/glucagon ratio causes decreased cAMP and reduced levels of protein kinase A.
2) Decreased protein kinase A favors dephosphorylation of PFK-2/FBP-2.
3) Dephosphorylated PFK-2 is active, whereas FBP-2 is inactive so fructose 2,6-bisphosphate forms.
4) Elevated fructose 2,6-bisphosphate activates PFK-1 which increases rate of glycolysis.

28
Q

Describe hormonal regulation of PFK in skeletal muscle.

A

1) Epinephrine binds Beta-adrenergic receptor which causes decreased cAMP and protein kinase A levels.
2) Decreased protein kinase A favors dephosphorylation of PFK-2/FBP-2 at a different site, forming a distinct isoform of PFK-2 that does not lead to its deactivation.
3) Fructose 2,6-bisphosphate forms.
4) Elevated fructose 2,6-bisphosphate activates PFK-1 which increases rate of glycolysis.

29
Q

What is the Cori Cycle?

A

Exercising muscles convert glucose to lactate. This lactate is taken up by the liver and reconverted to glucose using ATP (via gluconeogenesis). Glucose is released back into circulation

30
Q

What are the four potential fates of pyruvate?

A
  1. Ethanol fermentation (anaerobic)
  2. TCA cycle (anaplerotic rxn, gluconeogenesis) - becomes oxaloacetate
  3. Anaerobic metabolism - becomes lactate
  4. TCA cycle (energy) - becomes Acetyl CoA
31
Q

Which reaction of glycolysis is highly exergonic and favorable?

A

Glucose –> Glucose 6-phosphate (using hexokinase or glucokinase)

32
Q

How is PFK regulated by F26BP?

A

F26BP is an AMP-like signal that activates PFK and inhibits F1,6-BPase, upregulating glycolysis.

33
Q

What reaction can happen if someone lives at a high altitude? What enzymes are involved?

A

Mutase can convert 1-3 BPG to 2,3-BPG which binds to Hg and increases O2 off-loading to tissues. Phosphatase will get it back to 3-phosphoglycerate.

34
Q

What are the net products of aerobic glycolysis?

A

2 NADH, 2 ATP, 2 pyruvate

35
Q

How is pyruvate kinase regulated metabolically? Hormonally?

A

1) Metabolically: F 1,6-BP feed-forwards/activates PK
2) Hormonally: In liver, glucagon signaling increases CAMP levels, which increase PKA levels, which deactivates pyruvate kinase

36
Q

What are the net products of anaerobic glycolysis?

A

2 ATP, 2 lactate

37
Q

What enzyme is involved in anaerobic glycolysis?

A

Lactate dehydrogenase

38
Q

What molecule is recycled in anaerobic glycolysis?

A

NADH

Term I: Cell Biology (8 decks)

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