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Biochemistry > Glycolysis/Gluconeogenesis > Flashcards

Glycolysis/Gluconeogenesis Flashcards

1
Q

What is the net reaction for glycolysis?

A

glucose + 2 ADP + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH

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2
Q

What reaction is occurring here?

A

Phosphorylation

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3
Q

What Enzyme is this?

A

Hexokinase

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4
Q

What molecule is this?

A

Glucose

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5
Q

What molecule is this?

A

Glucose 6-Phosphate

G-6P

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6
Q

What reaction is occuring here?

A

isomerization

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7
Q

What Enzyme catalyzes this reaction?

A

Phosphoglucose Isomerase

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8
Q

What molecule is this?

A

Glucose 6-Phosphate

G-6P

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9
Q

What molecule is this?

A

Fructose 6-phosphate

F-6P

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10
Q

What reaction is occuring here?

A

phosphorylation

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11
Q

What Enzyme is this?

A

Phosphofructokinase

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12
Q

What molecule is this?

A

Fructose 6-Phosphate

F-6P

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13
Q

What molecule is this?

A

Fructose 1, 6-Biphosphate

F-1,6BP

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14
Q

What reaction is occuring here?

A

Cleavage

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15
Q

What Enzyme is this?

A

Aldolase

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16
Q

What molecule is this?

A

Fructose 1, 6-Biphosphate

F-1,6BP

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17
Q

What molecule is this?

A

Dihydroxyacetone Phosphate

DHAP

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18
Q

What molecule is this?

A

Glyceraldehyde 3-Phosphate

GAP

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19
Q

What reaction is occuring here?

A

isomerization

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20
Q

What Enzyme is this?

A

Triose Phosphate Isomerase

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21
Q

What molecule is this?

A

Dihydroxyacetone Phosphate

DHAP

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22
Q

What molecule is this?

A

Glyceraldehyde 3-Phosphate

GAP

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23
Q

What reaction is occuring here?

A

oxidation and phosphorylation

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24
Q

What Enzyme is this?

A

GAP Dehydrogenase

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25
Q

What molecule is this?

A

Glyceraldehyde 3-Phosphate

GAP

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26
Q

What molecule is this?

A

1,3-Biphosphoglycerate

1,3-BPG

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27
Q

What reaction is occuring here?

A

Dephosphorylation

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28
Q

What Enzyme is this?

A

Phosphoglycerate Kinase

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29
Q

What molecule is this?

A

1,3-Biphosphoglycerate

1,3-BPG

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30
Q

What molecule is this?

A

3-Phosphoglycerate

3-PG

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31
Q

What reaction is occuring here?

A

Rearrangement

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32
Q

What Enzyme is this?

A

Phosphoglycerate Mutase

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33
Q

What molecule is this?

A

3-Phosphoglycerate

3-PG

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34
Q

What molecule is this?

A

2-Phosphoglycerate

2-PG

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35
Q

What reaction is occuring here?

A

Dehydration

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36
Q

What Enzyme is this?

A

Enolase

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37
Q

What molecule is this?

A

2-Phosphoglycerate

2-PG

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38
Q

What molecule is this?

A

Phosphenolpyruvate

39
Q

What reaction is occuring here?

A

Dephosphorylation

40
Q

What Enzyme catalyzes this reaction?

A

Pyruvate Kinase

41
Q

What molecule is this?

A

Phosphenolpyruvate

42
Q

What molecule is this?

A

Pyruvate

(enol form)

43
Q

What molecule is this?

A

Pyruvate

44
Q

Under what conditions does glycolysis occur?

A

Anaerobic

45
Q

Pyruvate’s fate under _____ Conditions: NADH dump their e- into the Electron Transport Chain (ETC), where oxygen is the final e- acceptor. Pyruvate is further oxidized to acetyl-CoA by the Pyruvate Dehydrogenase Complex, and then enters into the Citric Acid Cycle

A

Aerobic

46
Q

Pyruvate’s fate under ______ Conditions: ETC does not run and the NADH from glycolysis have nowhere to dump their e-, fermentation in yeast, reduced to lactate

A

Anaerobic

47
Q

What are the 3 main enzymes that regulate glycolysis?

A
  1. Hexokinase
  2. Phosphofructokinase (most important)
  3. Pyruvate kinase
48
Q

Where is the following true?

• Hexokinase:

– Regulated by feedback inhibition of its product (G-6-P)

– Allows glucose export from cell

• Phosphofructokinase:

– Regulated allosterically by ATP/AMP and pH

– ATP and low pH down-regulate glycolysis; AMP upregulates

• Pyruvate kinase:

– Allosterically regulated by ATP/ADP

– Inhibited by alanine (biosynthesis pathway)

– Stimulated through feed-forward mechanism by F-1,6-BP

A

Muscle

49
Q

Where is the following true?

• Hexokinase:

– Regulated by feedback inhibition of its product (G-6-P)

– Hexokinase D functions only under high levels of glucose

– Provides G-6-P for glycogen synthesis

• Phosphofructokinase:

– Inhibited by citrate, an early intermediate of the TCA cycle

– Activated by fructose 2,6-bisphosphate (F-2,6-BP), an alternative product formed under high F-6-P levels

• Pyruvate kinase:

– Regulated through covalent modification via ATP phosphorylation of the enzyme

A

Liver

50
Q

What reaction is occuring here?

A

carboxylation

51
Q

What Enzyme is this?

A

Pyruvate Carboxylase

52
Q

What molecule is this?

A

Pyruvate

53
Q

What molecule is this?

A

Oxaloacetate

54
Q

What reaction is occuring here?

A

decarboxylation and phosphorylation

55
Q

What Enzyme catalyzes this reaction?

A

PEP Carboxykinase

56
Q

What molecule is this?

A

oxaloacetate

57
Q

What molecule is this?

A

Phosphenolpyruvate

PEP

58
Q

What reaction is occuring here?

A

dephosphorylation

59
Q

What Enzyme is this?

A

Fructose-1,6-biphosphatase

60
Q

What molecule is this?

A

Fructose-1,6-biphosphate

F-1,6-BP

61
Q

What molecule is this?

A

Fructose-6-phosphate

62
Q

What reaction is occuring here?

A

dephosphorylation

63
Q

What Enzyme is this?

A

Glucose-6-phosphatase

64
Q

What molecule is this?

A

Glucose-6-phosphate

65
Q

What molecule is this?

A

Glucose

66
Q

What is the net yield of ATP from glucose in glycolysis?

A

2

67
Q

What is pyruvate’s fate under aerobic conditions? Anaerobic conditions?

A
  • Under aerobic conditions the NADH formed dump their e- into the ETC (where oxygen is the final e- acceptor).
  • Under anaerobic conditions i.e. low or no oxygen, ETC does not run and NADH from glycolysis has nowhere to dump their e- (and thus cannot regenerate NAD+ which is in limited supply)

Reaction occurs best in anaerobic conditions.

68
Q

What is kinetics? Allosterism? Compartmentalization?

A
  1. Control the amount of enzyme (kinetics)
  2. Control their catalytic activity (allosterism)
  3. Control accessibility of substrates (compartmentalization)
69
Q

How is glycolysis regulated in muscle?

A
  • In muscle, phosphofructokinase is regulated by ATP/AMP and pH. Classic allosterism
  • ATP and pH down-regulate glycolysis and AMP upregulates.
  • Hexokinase is regulated by classic feedback inhibition by its product (G-6-P). Allows G export from cell.
  • Pyruvate kinase is also regulated by ATP/ADP allosterism and inhibited by alanine (biosynthesis pathway) and is stimulated through a feed forward mechanism by F-1,6-BP.
70
Q

How is glycolysis regulated in the liver?

A

In the liver, there is little ATP or pH

flux as seen in muscle (thus these are not regulators of PFK) . Citrate is a biomolecule in the CAC pathway that can cross the mitochondria and signal a high state of energy (thus it will downregulate glycolysis in liver)

71
Q

Why does a CO2 group get temporarily added on to pyruvate only to be taken off?

A

Pyruvate carboxylase is a mitochondrial enzyme thus, oxaloacetate must be transported from mitochondria to cytoplasm for gluconeogenesis to continue.

72
Q

How is blood glucose related to glycolysis and glyconeogenesis?

A
  • Blood [Glucose] high = glycolysis
  • Blood [Glucose] low = gluconeogenesis

–Irrespective of physical activity level and cellular energy demand. Remember, this is liver.

73
Q

Hexokinase activation

A

Feedback inhibition but also enzymatic isoforms of low level activity

74
Q

Phosphofructokinase activation

A

M = muscle; L = Liver

(M): Inhibited by high ATP levels; Activated by high AMP levels

(M): Inhibited by low pH (acid)

(L): inhibited by citrate

75
Q

Pyruvate Kinase activation

A

Activated by F-1,6-BP in a feed forward mechanism

Inhibited by ATP; activated by ADP

Inhibited by alanine

Activated by epinephrine; inhibited by glucagon in signal transduction via phosphorylation

76
Q

Pyruvate Carboxylase activation

A

Activated by glucagon; inhibited by insulin

Activated by Acetyl CoA; inhibited by CoA

77
Q

F-1,6-bisphosphatase activation

A

Citrate enhances

AMP inhibits

78
Q

What is oxaloacetate reduced to for transport across the mitochondrial membrane?

A

Malate

79
Q

Where does Conversion of G-6-P to glucose occur?

A

Only in the ER of liver cells, where glucose 6-phosphatase is found

80
Q

What is consumed during gluconeogenesis?

A

4 ATP, 2 GTP, and 2 NADH

81
Q

What other non-carbohydrate precursors can be converted into glucose?

A

Lactate: from muscle following strenuous exercise enters as pyruvate

Amino acids (alanine): transamination product of pyruvate enters as pyruvate

Glycerol: from triacylglycerol breakdown enters as DHAP

82
Q

Where does the regulation of gluconeogenesis and glycolysis occur?

A

The liver

83
Q

Which two steps of glycolosis use ATP?

A

Glucose to G-6P via hexokinase

F-6P to F-1,6-BP via phosphofructokinase

84
Q

Which two steps of glycolosis produce ATP?

A

1,3-BPG to 3-PG via phosphoglycerate kinase

PEP to Pyruvate via pyruvate kinase

85
Q

Which step of glycolosis produces NADH?

A

GAP to 1,3-BPG via GAP dehydrogenase

86
Q

Which step of glycolysis releases H2O?

A

2-PG to PEP via enolase

87
Q

What molecule is this?

A

Pyruvate

88
Q

What enzyme is this?

A

Pyruvate Carboxylase

89
Q

What molecule is this?

A

Oxaloacetate

90
Q

What enzyme is this?

A

Phosphoenolpyruvate Carboxykinase

91
Q

What molecule is this?

A

Phospenolpyruvate (PEP)

92
Q

What molecule is this?

A

Malate

93
Q

What enzyme is this?

A

Malate dehydrogenase

94
Q

What molecule is this?

A

Oxaloacetate

Biochemistry (12 decks)

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