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SMP - MNE Exam 1 > Lecture 15: Glycolysis & Pentose Phosphate Pathway > Flashcards

Lecture 15: Glycolysis & Pentose Phosphate Pathway Flashcards

1
Q

What 2 steps of glycolysis use ATP?

A

Steps 1 and 3

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2
Q

What 2 steps of glycolysis produce ATP?

A

Steps 7 and 10

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3
Q

Why is ATP used in steps 1 and 3 of glycolysis?

A

Because the free energy level of the beta-gamma bond of ATP is higher than the free energy of the phosphate linkages in G6P and F1,6BP (extra energy is heat)

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4
Q

Why is ATP produced in steps 7 and 10 of glycolysis?

A

Because the free energy level of the phosphate linkages in 1,3BPG and phosphoenolpyruvate is higher than the beta-gamma bond of ATP (extra energy is heat)

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5
Q

Glycolysis step 1 enzyme?

A

Hexokinase

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6
Q

Glycolysis step 1: reversible or irreversible?

A

Irreversible

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7
Q

Glycolysis step 1: ΔG°’?

A

Large negative ΔG°’ (-16.7 kJ/mol)

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8
Q

What is the main purpose of the 1st step of glycolysis?

A

Retain glucose in the cell

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9
Q

What is the 1st priming rxn of glycolysis?

A

Step 1

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10
Q

Glycolysis step 2 enzyme?

A

Phosphohexose isomerase

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11
Q

Glycolysis step 2: reversible or irreversible?

A

Reversible

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12
Q

Glycolysis step 2: ΔG°’?

A

Small positive ΔG°’ (1.7 kJ/mol)

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13
Q

Glycolysis step 3 enzyme?

A

Phosphofructokinase-1 (PFK-1)

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14
Q

Which is the second priming step of glycolysis?

A

Step 3

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15
Q

What is the first committed step of glycolysis?

A

Step 3

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16
Q

Glycolysis step 2 reactant and product?

A

G6P –> F6P

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17
Q

Glycolysis step 3 reactant and product?

A

F6P –> F1,6BP

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18
Q

Glycolysis step 3: ΔG°’?

A

Large negative ΔG°’ (-14.2 kJ/mol)

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19
Q

How is step 3 of glycolysis regulated?

A

Allosterically:

Activated by:
- F2,6BP (feed-forward regulation)
- AMP/ADP
Inhibited by:
- ATP
- Citrate (feedback inhibition)
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20
Q

Explain how PFK-1 is regulated by F2,6BP.

A

F6P is high –> activates PFK-2 –> converts F-6P to F-2,6-BP –> stimulates PFK-1

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21
Q

What is citrate a marker of in inhibiting PFK-1?

A

FA synthesis because acetyl-CoA needs to be transported to the cytoplasm via the citrate shuttle, so if you have enough of it that means you have enough citrate for FA synthesis

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22
Q

Glycolysis step 4 enzyme?

A

Aldolase

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23
Q

Glycolysis step 4 reactant and product?

A

F1,6BP –> DHAP + GAP

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24
Q

Glycolysis step 4: ΔG°’?

A

Large positive ΔG°’ (23.8 kJ/mol)

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25
Q

Glycolysis step 3: reversible or irreversible?

A

Irreversible

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26
Q

Glycolysis step 4: reversible or irreversible?

A

Reversible

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27
Q

What does GAP stand for?

A

Glyceraldehyde-3-phosphate

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28
Q

What does DHAP stand for?

A

Dihydroxyacetone phosphate

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29
Q

What is DHAP a precursor for?

A

Tryacylglycerol synthesis

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30
Q

Glycolysis step 5 enzyme?

A

Triose Phosphate Isomerase (TPI)

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31
Q

Glycolysis step 5 reactant and product?

A

DHAP –> GAP

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32
Q

Glycolysis step 5: ΔG°’?

A

Small positive ΔG°’ (7.5 kJ/mol)

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33
Q

Glycolysis step 5: reversible or irreversible?

A

Reversible

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34
Q

What steps does the preparatory phase of glycolysis include?

A

Steps 1-5

35
Q

How many GAP molecules produced per 1 glucose?

A

2

36
Q

Glycolysis step 6 enzyme?

A

Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH)

37
Q

Glycolysis step 6 reactants and products?

A

GAP + Pi + NAD+ –> 1,3-bisphosphoglycerate + NADH + H+

38
Q

Glycolysis step 6: ΔG°’?

A

Small positive ΔG°’ (6.3 kJ/mol)

39
Q

Glycolysis step 6: reversible or irreversible?

A

Reversible

40
Q

What steps does the payoff phase of glycolysis include?

A

6-10

41
Q

Explain how NADH is generated in step 6 of glycolysis? What is the rest of the energy used for?

A

The electrons on the aldehyde group of GAP are high in energy and are transferred to NAD+
Rest of energy used to form acyl-phosphate covalent bond that is very high in energy

42
Q

Glycolysis step 7 enzyme?

A

Phosphoglycerate kinase

43
Q

Glycolysis step 7 reactants and products?

A

1,3BPG + ADP –> 3-phosphoglycerate + ATP

44
Q

Glycolysis step 7: ΔG°’?

A

Large negative ΔG°’ (-18.5 kJ/mol)

45
Q

Glycolysis step 7: reversible or irreversible?

A

Reversible

46
Q

What bond in 1,3BPG is high in energy?

A

Acyl phosphate bond

47
Q

How many ATP produced in step 7 of glycolysis per glucose?

A

2 ATP

48
Q

Glycolysis step 8 enzyme?

A

Phosphoglycerate mutase

49
Q

Glycolysis step 8 reactants and products?

A

3-phosphoglycerate –> 2-phosphoglycerate

50
Q

Glycolysis step 8: ΔG°’?

A

Small positive ΔG°’ (4.4 kJ/mol)

51
Q

Glycolysis step 8: reversible or irreversible?

A

Reversible

52
Q

Glycolysis step 9 enzyme?

A

Enolase

53
Q

Glycolysis step 9 reactants and products?

A

2-phosphoglycerate –> phosphoenolpyruvate + H2O

54
Q

Glycolysis step 9: ΔG°’?

A

Small positive ΔG°’ (7.5 kJ/mol)

55
Q

Glycolysis step 9: reversible or irreversible?

A

Reversible

56
Q

Glycolysis step 10 enzyme?

A

Pyruvate kinase

57
Q

Glycolysis step 10 reactants and products?

A

Phosphoenolpyruvate + ADP –> pyruvate + ATP

58
Q

Glycolysis step 10: ΔG°’?

A

Large negative ΔG°’ (-31.4 kJ/mol)

59
Q

Glycolysis step 10: reversible or irreversible?

A

Irreversible

60
Q

What is the net reaction of the oxidation of 1 glucose through glycolysis?

A

1 glucose + 2 ATP + 2 NAD+ –> 2 pyruvate + 4 ATP + 2 NADH + 2 H+ + 2 H2O

61
Q

What are the 2 ways of regenerating NAD+ for step 6 of glycolysis? Which one is fastest?

A
  1. Aerobically in mito

2. Anaerobically in cytosol = fermentation (FASTEST)

62
Q

Describe the aerobic regeneration of NAD+ in the mito. Equation?

A

2 NADH + 2 H+ + O2 –> 2 NAD+ +2 H2O

NADH needs a carrier to enter the mito matrix so this step is slow

63
Q

Describe the anaerobic regeneration of NAD+ in the cytosol = fermentation. Equation?

A

Pyruvate –> L-lactate by lactate dehydrogenase

Rapid regeneration

64
Q

Where can fermentation occur?

A

Muscles, RBCs, and other tissues

65
Q

What is the pentose phosphate pathway?

A

It’s the pathway taken by G6P if glycolysis is inhibited to generate 2 NADPH and ribose-5-phosphate

66
Q

What is ribose-5-phosphate created by the PPP used for?

A
  1. De novo ATP synthesis

2. Nucleotide synthesis

67
Q

What is NADPH created by the PPP used for?

A
  1. Biosynthesis of FAs and sterols

2. Converts GSSG to 2GSH

68
Q

What are the 2 phases of the PPP and what happens in each?

A
  1. Oxidative: generation of 2 NADPH and ribose-5-phosphate (CO2 leaves)
  2. Nonoxidative: ribulose-5-phosphate regenerates G6P
69
Q

What are the 2 enzymes of the PPP that generate NADPH?

A
  1. G6P dehydrogenase (G6PD)

2. 6-phosphogluconate dehydrogenase

70
Q

What is the purpose of NADPH converting GSSG to 2GSH?

A

Protect the body from oxidizing agents:
Small amount of O2 in cells is converted to ROS (superoxide radicals, hydrogen peroxide, and hydroxyl free radicals) and gluthathione peroxidase can convert these to water by using the reducing power of GSH (which is converted back to GSSG)

71
Q

How is GSSG converted to 2GSH?

A

Gluthatione reductase use NADPH’s reducing power

72
Q

What does GSH stand for? Does it have disulfide bonds?

A

Reduced gluthathione

No disulfide bonds

73
Q

What does GSSG stand for? Does it have disulfide bonds?

A

Oxidized gluthathione

1 disulfide bond

74
Q

What is favism? Symptoms? Treatment?

A

Condition caused by lack of G6PD enzyme and foods that have divicine (like fava beans): too many ROS in RBCs and no NADPH to protect the body
Symptoms: anemia, diarrhea, respiratory problems, can be lethal
Treatment: avoid oxidizing agents in diet

75
Q

Describe the nonoxidative phase of the PPP. What 2 enzymes are used?

A

Six 5-carbon molecules are converted to five 6-carbon
molecules, thus regenerating glucose 6-phosphate.
1. Transketolase
2. Transaldolase

76
Q

Which steps of glycolysis are irreversible?

A

1, 3, and 10

77
Q

Other than 1,3BPG and phosphoenolpyruvate, what other molecule has a phosphate linkage that is higher in energy than ATP’s?

A

Phosphocreatine

78
Q

Which produces ATP the fastest: glycolysis or ETC?

A

Glycolysis

79
Q

What is the definition of fermentation?

A

Generating ATP from a metabolic fuel without net oxidation of the fuel

80
Q

Which organs have the enzyme PFK2?

A

Skeletal muscles

81
Q

Why do patients with favism not have a ribose-5-phosphate caused deficiency in nucleotides?

A

Because nucleotides can be obtained in the diet

82
Q

What are 2 important glycolytic intermediates does the nonoxidative phase of the PPP generate?

A
  1. F6P

2. GAP

83
Q

Does the PPP involve the oxidation of glucose?

A

Yes

84
Q

Is the PPP anabolic or catabolic?

A

Anabolic

SMP - MNE Exam 1 (25 decks)

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