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Intermediary Metabolism > Glycolysis - Substrate and Product structures and enzymes > Flashcards

Glycolysis - Substrate and Product structures and enzymes Flashcards

1
Q

Write down the names of the substrates and products of each reaction of glycolysis.

A

glucose - (hexokinase) - glucose-6-phosphate - (phosphoglucose isomerase) - fructose-6-phosphate - (phosphofructokinase) - Fructose-1,6-biphosphate - (Aldolase) - GAP + DHAP - (Triose phosphate isomerase) - GAP * 2 - (Glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) - 1,3-biphosphoglycerate - (phosphoglycerate kinase) - 3-phosphoglycerate - (phosphoglycerate mutase) - 2-phosphoglycerate - (enolase) - phosphoenolpyruvate - (pyruvate kinase) - pyruvate

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2
Q

Write down the steps with the input/output of ATP, NADH, H2O and Mg2+/K+

A

Refer to page 474

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3
Q

Draw all the substrates and products of glycolysis.

A

Refer to page 474

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4
Q

Draw Glucose.

A

Refer to page 474

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5
Q

Draw G6P

A

Refer to page 474

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6
Q

Draw F6P

A

Refer to page 474

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7
Q

Draw FBP

A

Refer to page 474

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8
Q

Draw GAP

A

Refer to page 474

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9
Q

Draw DHAP

A

Refer to page 474

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10
Q

Draw 1,3-BPG

A

Refer to page 474

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11
Q

Draw 3PG

A

Refer to page 474

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12
Q

Draw 2PG

A

Refer to page 474

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13
Q

Draw PEP

A

Refer to page 474

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14
Q

Draw pyruvate

A

Refer to page 474

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15
Q

Which enzyme converts glucose to G6P?

A

hexokinase

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16
Q

Which enzyme converts G6P to F6P?

A

phosphoglucose isomerase

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17
Q

Which enzyme converts F6P to FBP?

A

phosphofructokinase

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18
Q

Which enzyme converts FBP to DHAP and GAP?

A

aldolase

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19
Q

Which enzyme converts DHAP to GAP?

A

triose phosphate isomerase

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20
Q

Which enzyme converts GAP to 1,3-BPG?

A

glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

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21
Q

Which enzyme converts 1,3-BPG to 3PG?

A

phosphoglycerate kinase

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22
Q

Which enzyme converts 3PG to 2PG?

A

phosphoglycerate mutase

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23
Q

Which enzyme converts 2PG to PEP?

A

enolase

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24
Q

Which enzyme converts PEP to pyruvate?

A

Pyruvate kinase

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25
Q

Draw the mechanism for GADPH.

A

Refer to notes

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26
Q

Draw the mechanism for PGM.

A

Refer to notes.

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27
Q

Draw the mechanism for enolase.

A

Refer to notes

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28
Q

Draw the mechanism for alcoholic fermentation

A

Refer to notes

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29
Q

Draw the mechanism for homlactic fermentation.

A

Refer to notes

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30
Q

What type of reaction is the GAPDH reaction?

A

Nucleophilic attack - SN2
Oxidation reaction (Dehydrogenation)
Nucleophilic attack - SN2

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31
Q

What type of reaction is the alcoholic fermentation reaction using TPP?

A

SN1

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32
Q

What type of reaction is the alcoholic fermentation reaction with alcohol dehydrogenase?

A

Oxidation to reform NAD+.

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33
Q

What is the enzyme of reaction 1?

A

Hexokinase

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34
Q

What is the enzyme of reaction 2?

A

Phosphoglucose isomerase or phosphohexose isomerase

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35
Q

What is the enzyme of reaction 3?

A

Phosphofructokinase

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36
Q

What is the enzyme of reaction 4?

A

aldolase

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37
Q

What is the enzyme of reaction 5?

A

Triose phosphate isomerase

38
Q

What is the enzyme of reaction 6?

A

glyceraldehyde-3-phosphate dehydrogenase

39
Q

What is the enzyme of reaction 7?

A

Phosphoglycerate kinase

40
Q

What is the enzyme of reaction 8?

A

Phosphoglycerate mutase

41
Q

What is the enzyme of reaction 9?

A

enolase

42
Q

What is the enzyme of reaction 10?

A

Pyruvate kinase

43
Q

What is/are the substrates of reaction 1? (in the forward direction)

A

ATP-Mg2+ and glucose

44
Q

What is the mechanism of reaction 1?

A

Proximity effects.
Two binding sites for ATP-Mg2+ and glucose. Upon binding, changes confirmation, bringing the substrates together to cause the reaction to occur instantaneously.

45
Q

What is/are the inhibitor(s) of reaction 1?

A 
Competitive inhibitor - ATP (uncomplexed)
Allosteric inhibitor (G6P)
46
Q

Reaction 1, in the forward direction is: exergonic or endergonic?

A

Exergonic

47
Q

Do cancer cells upregulate or downregulate hexokinase?

A

upregulate

48
Q

Under what conditions does uncomplexed ATP accumulate?

A

When energy is barely used and thus, ATP is plentiful. Mg2+ is no longer able to complex with all the ATP so glycolysis is interrupted and glycogen is made instead.

49
Q

What is the substrate of reaction 2 in the forward direction?

A

G6P

50
Q

What is the mechanism for reaction 2?

A

MG2+ is required!

Specific for G6P/F6P

51
Q

What is the main control for this reaction (2) and, what can be inferred from this?

A

The main control is concentration. We can infer that this reaction is reversible and that delta G is nearly zero.

52
Q

G6P is a(n) _____hexose whilst F6P is a(n) _____hexose.

A

aldohexose - G6P

ketohexose - F6P

53
Q

What is the enzyme of reaction 3?

A

Phosphofructokinase-1

54
Q

What is/are the substrate(s) of reaction 3 in the forward direction?

A

ATP-Mg2+ and F6P

55
Q

How is this enzyme (PFK-1) controlled? What are its inhibitors/activators?

A

Important enzyme for regulation.
ATP and citrate are both inhibitors.
ATP is an allosteric inhibitor.
ADP, AMP and Fructose-2,6-biphosphate are allosteric activators.

56
Q

What is adnylate kinase?
What occurs if ATP concentration is decreased?
If the kinase is active, what accumulates?

A

Enzyme that readily equilibrates 2 ADP into 1 ATP and 1 AMP.
Enzyme that is active when ATP levels are low and ADP levels are high.
K = [ATP][AMP]/[ADP]^2
Decreased ATP –> pushes reaction forward
If the kinase is active, AMP accumulates.

57
Q

What are other features of this reaction (3)?

A

Commits the cell to glycolysis.

Very exergonic

58
Q

What is/are the substrate(s) of reaction 4?

A

FBP

59
Q

What is the mechanism of reaction 4?

A

Aldolase catalyzes the cleavage of FBP by aldol condensation mechanism.
Products of this reaction are depleted rapidly and this reaction is pulled forward by reactions 5 and 6.

60
Q

How is reaction 4 pulled forward if it is endergonic?

A

Reactions 5 and 6 quickly deplete the products of this reaction, pulling it forward.

61
Q

How is reaction 4 controlled?

A

concentration control

62
Q

What is the mechanism for reaction 5?

A

Reversible reaction catalyzed by acid-based catalysis. His95 and Glu165 of the enzyme are involved.

63
Q

How is reaction 5 controlled?

A

endergonic, pulled forward as product is used up.

64
Q

What occurs if step 5 is blocked?

A

Glycolysis proceeds at half the rate.

65
Q

What is the most important fact about reaction 6?

A

It’s the reaction responsible for the generation of energy in glycolysis as a whole.

66
Q

Once again, reaction 6 is endergonic, how is it pulled foward?

A

Pulled forward by reaction 7.

1,3-BPG is very unstable.

67
Q

In reaction 6, an _______ is converted to a _______ group.

A

aldehyde –> carboxyl

68
Q

In reaction 6, oxidation of the aldehyde does two things. These are?

A

1 - Make a high-energy phosphate bond

2 - Produce a reduced moiety (NADH)

69
Q

What is the oxidizing agent of this reaction? (6)

A

NAD+, which is reduced to NADH

70
Q

What drives the formation of acylphosphate during reaction 6?

A

Free energy from the oxidation reaction.

71
Q

What is the evidence supporting the GADPH reaction?

A

1 - Iodoacetate inhibits this reaction, indicating the involvement of a cysteine residue of the enzyme
2 - Tritium from GAP is trasnferred directly to NAD which indicates that the hydrogen transfer is under the form of a hydride ion
3 . Labelled ATP does not cause the product to be labelled. Pi is instead transferred providing evidence for the acyl enzyme intermediate.

72
Q

What are the substrates for reaction 7?

A

1,3-BPG and ADP-Mg2+

73
Q

What is the mechanism for reaction 7?

A

Proximity effect.
Coupled to reaction 6.
ATP is generated by substrate-level phosphorylation

74
Q

Where does the energy for this reaction come from? What is one reason for 1,3-BPG being desperate to hydrolyze?

A

Energy for this reaction comes from the highly energetic 1,3-BPG.
3-PG is resonance hybridized.

75
Q

In reaction 8, something is very rarely recorded in the mixture. What is it?

A

2,3-BPG

76
Q

What is the enzyme for reaction 8 and what is important about it?

A

Phosphoglycerate mutase.

Phosphorylated His-179 residue.

77
Q

Is the product of the forward reaction of step 8 stable or not?

A

2-PG is stable

78
Q

What is the mechanism for reaction 9?

A

Dehydration of 2-PG.
1 - Rapid extraction of a proton at C-2 by a general base of the enzyme, generating a carbanion
b - abstracted proton easily exchanged with solvent
2 - Rate limiting elimination of OH

79
Q

How do we know that the exchange in reaction 9 involves a proton?

A

Tritiated 2-PG will cause water to become labeled. Thus, the exchange does not involve a hydride ion.

80
Q

What are the special requirements for reaction 10?

A

K+ and Mg2+ are required.

81
Q

PEP is desperate to hydrolyze. True or false?

A

True, the reaction is very exergonic

82
Q

What reactions are:

a) oxidation reaction
b) substrate-level phosphorylation
c) phosphorylations
d) isomerizations
e) dehydrations
f) carbon-carbon bond cleavage

A

a) 6
b) 7, 10
c) 1, 3, 7, 10
d) 2, 5
e) 9
f) 4

83
Q

Is reaction 1 exergonic, endergonic or reversible?

A

exergonic

84
Q

Is reaction 2 exergonic, endergonic or reversible?

A

Reversible

85
Q

Is reaction 3 exergonic, endergonic or reversible?

A

Exergonic

86
Q

Is reaction 4 exergonic, endergonic or reversible?

A

Endergonic

87
Q

Is reaction 5 exergonic, endergonic or reversible?

A

Endergonic/reversible

88
Q

Is reaction 6 exergonic, endergonic or reversible?

A

Endergonic

89
Q

Is reaction 7 exergonic, endergonic or reversible?

A

Exergonic

90
Q

Is reaction 8 exergonic, endergonic or reversible?

A

endergonic/reversible

91
Q

Is reaction 9 exergonic, endergonic or reversible?

A

Endergonic

92
Q

Is reaction 10 exergonic, endergonic or reversible?

A

Exergonic

Intermediary Metabolism (13 decks)

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