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Metabolism > 2. Glycolysis > Flashcards

2. Glycolysis Flashcards

1
Q

During this process one molecule of __________ (6 carbon molecule) is degraded into two molecules of __________ (three carbon molecule).

A

glucose

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2
Q

Free energy released in this process is stored as ____ molecules of __________, and ____ molecules of __________.

A

2 ATP

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3
Q

Provide the 2 chemical equations of glycolysis, indicating which one has a negative and positive free energy change:

A

Glucose + 2NAD+ = 2Pyruvate + 2NADH + 2H+ (negative free E)

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4
Q

In standard condition glycolysis is an exergonic reaction which tends to be irreversible because of negative dGo. True or false?

A

TRUE

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5
Q

____% of total free energy that can be released by glucose is released in glycolysis.

A

5.2

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6
Q

What are the 3 different fates of glucose?

A
  1. STORAGE –> glycogen, starch, sucrose
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7
Q

Pasteur’s effect

A

Aerobic growth requires less glucose than anaerobic condition. (more consumption of sugar in anaerobic)

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8
Q

What did Buchner discover?

A

Reactions of glycolysis can be carried out in cell-free yeast extract.

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9
Q

What did Harden and Young discover? (2)

A

1: inorganic phosphate is required for fermentation.

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10
Q

What were the 2 major inhibitor studies of glycolysis?

A

Iodoacetate treatment resulted in the accumulation of fructose 1,6biphosphate.

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11
Q

Get info from slide 6 on importance of phosphorylated intermediates

A

Okay

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12
Q

Importance of phosphorylated intermediates: (3)

A

1.Possession of NEGATIVE CHARGE which inhibit their diffusion through membrane.

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13
Q

What is the preparatory phase of glycolysis?

A

Phosphorylation of glucose and its conversion to glyceraldehyde 3-phosphate (Rxns 1-5)

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14
Q

What is the payoff phase of glycolysis?

A

Oxidative conversion of glyceraldehyde 3-phosphate to pyruvate and the coupled formation of ATP and NADH

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15
Q

Provide the names of all glycolysis structures in order with the respective inputs and outputs and draw their structures

A

Looking back, I am ashamed of this question.

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16
Q

What are the 2 extremely important things that take place in reaction 6?

A

Oxidation from aldehyde to carboxylate yielding NADH and phosphorylation via inorganic phosphate

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17
Q

This inorganic phosphate drives the formation of net ATP. true or false?

A

TRUE

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18
Q

Also, name the substrates involved and inhibitors.

A

Hexokinase reaction: phosphorylation of glucose by hexokinase

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19
Q

This enzyme undergoes large conformational change upon binding with Glucose. True or false?

A

TRUE

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20
Q

In the liver, ____________ is the main hexokinase which prefers glucose as substrate

A

glucokinase

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21
Q

Why are un-complexed ATP and G6P very fitting as inhibitors?

A

Because if a lot of ATP is around, we don’t need more glycolysis and if a lot of G6P is around then we don’t need to do the first step much anymore

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22
Q

Name and describe the 2nd reaction of glycolysis, including what the enzyme requires for its activity:

A

Phosphohexose isomerase (or phosphoglucose isomerase) –> isomerization of G6P to F6P

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23
Q

Provide rough free energy value and explain why this rxn is favoured:

A

near zero but gets favoured because concentration of product is really low as a result of a highly exergonic 3rd step, so reaction is driven forward.

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24
Q

Also include free energy sign.

A

Phosphofructokinase-1 reaction: irreversible transfer of phosphoryl group from ATP to C-1 of F6P to produce F-1,6-P

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25
Q

Describe phosphofructokinase-1 regulation:

A

ATP (allosteric) and citrate are inhibitors

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26
Q

Also, name and describe its free energy situation:

A

Aldolase Reaction: Cleavage of Fructose 1,6 bisphosphate into glyceraldehyde 3 phosphate (an aldose) and dihydroxyacetone phosphate (a ketose).

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27
Q

Describe what aldolase does mechanistically:

A

cleaves f16bisphosphate by aldol condensation mechanism

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28
Q

Name and describe the 5th of glycolysis:

A

Triose phosphate isomerase: Conversion of Dihydroxyacetone phosphate to glyceraldehyde 3 Phosphate.

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29
Q

It is endergonic/exergonic.

A

reversible

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30
Q

Name and briefly describe what happens in 6th reaction:

A

Glyceraldehyde-3-phosphate dehydrogenase reaction (GAPDH): Conversion of GAP to 1,3-Bisphosphoglycerate

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31
Q

Remember harden and young found out that if u get rid of ___________ phosphate, reaction 6 doesn’t happen meaning glycolysis will stop

A

phosphoanhydride

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32
Q

NAD+ is a ___________, BUT ALSO acts as ___________ , taking away hydrogen

A

co-factor

33
Q

What is the oxidizing agent in step 6?

A

NAD+

34
Q

Evidence for the GAPDH reaction mechanism:

A

I.Iodoacetate inhibits this reaction, indicating the involvement of Cystine residue of enzyme.

35
Q

List the steps to the reaction 6 mechanism and draw it:

A

1.Glyceraldehyde 3 phosphate (GAP) binding to the enzyme.

36
Q

Also indicate how the enzyme catalyzes the reaction.

A

Phosphoglycerate Kinase Reaction: Transfer of phosphoryl group fron 1,3 bisphosphoglycerate to ADP generating ATP.

37
Q

Indicate the free energy situation in reaction 7.

A

6th step and 7th step are coupled to generate the ATP from energy released by oxidation of GAP. 6th step is endergonic, 7th is exergonic.

38
Q

The name for the 7th reaction indicates the enzymatic function for the reverse reaction. True or false?

A

TRUE

39
Q

This step generates ATP by _____________-_____________ _____________.

A

substrate level phosphorylation

40
Q

Name and briefly describe the 8th reaction of glycolysis.

A

Phosphoglycerate Mutase Reaction: Conversion of 3-phosphoglycerate to 2-phosphoglycerate (2-PG).

41
Q

Provide the steps for the mechanism of reaction 8 and draw it out:

A
  1. 3-PG binds to phosphoglycerate mutase active site.
42
Q

In most cells 2,3BPG is present in trace amount, but in _____________ it is present in significant amount. There it regulates _____________ affinity to _____________ .

A

erythrocytes

43
Q

Also, indicate the free energy situation.

A

Enolase Reaction: Dehydration of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP).

44
Q

Describe the mechanism for step 9 and draw it:

A
  1. Binding of 2-PG to active site of enolase
45
Q

Name and briefly describe the 10th reaction of glycolysis:

A

Pyruvate kinase reaction: transfer of phosphoryl group from PEP to ADP generating ATP and Pyruvate. (Sub-level phosphorylation)

46
Q

What does the 10th reaction require?

A

Mg2+ and K+

47
Q

Name is for the reverse reaction again. True or false?

A

TRUE

48
Q

Why is the 10th reaction so favoured?

A

Pyruvate is resonance stabilized and can tautomerize!

49
Q

Draw the 2 forms of pyruvate:

A

Slide 25

50
Q

After balancing, provide chemical equation for glycolysis:

A

1Gl + 2NAD++ 2ADP + 2Pi = 2pyruvate+2ATP + 2NADH

51
Q

The ___ NADH molecules are oxidized in mitochondria under aerobic condition and the free energy released is enough to synthesize ____ molecules of ATP by oxidative phosphorylation

A

2

52
Q

Under the aerobic condition, pyruvate is catabolized further in mitochondria through ______________ ______________ and ______________ ______________ ______________ where all the carbon atoms are oxidized to ______________ . The free energy released is used in the synthesis of ATP, NADH and FADH2.

A

pyruvate dehydrogenase

53
Q

Pyruvate is converted to __________ in __________ fermentation in ___________ or to __________ in __________ fermentation in ___________

A

lactate; homolactic; mammals (and some microorganisms)

54
Q

1 Glucose = ____ pyruvate = ____ lactate

A

2

55
Q

1 Glucose = ___ pyruvate = ____ ethanol + ___ co2

A

2

56
Q

How do you make acetylcoa

A

2 pyruvate = 2co2 + 2acetyl coA

57
Q

2 Acetyl CoA = ___co2 + ___h2o

A

4

58
Q

Describe why homolactic fermentation is needed, what happens and where? What is the ultimate result?

A

Homolactic fermentation is needed in anaerobic conditions or in a sudden need of a lot of ATP. NAD+ needs to be regenerated in order to run the GAPDH reaction in which NAD+ is the oxidizing agent.

59
Q

Provide a full representation of homolactic fermentation (structures, names, enzymes, reactants, products, free energy)

A

Slide 28

60
Q

true or false?

A

TRUE

61
Q

Describe why alcohol fermentation is needed and what happens. What enzymes are involved?

A

Regenerate NAD+

62
Q

Indicate what each enzyme does in alcoholic fermentation and what they require to do so. (TWO steps)

A

1.Pyruvate decarboxylase (PDC) reaction: This enzyme is Mg++-dependent and requires an enzyme-bound cofactor, thiamine pyrophosphate (TPP). In this reaction a molecule of CO2 is released producing acetaldehyde.

63
Q

What is seen in anaerobic processes compared to aerobic?

A

pasteur effect - more sugar consumption

64
Q

Draw the functional group of thiamine pyrophosphate (TPP) involved in the mechanism (thiazolium ring):

A

slide 31

65
Q

Describe the reaction mechanism of pyruvate decarboxylase and draw it out:

A
  1. Hydrogen comes off TPP to form a TPP anion that does a nucleophilic attack on carbonyl carbon of pyruvate.
66
Q

Describe the alcohol dehydrogenase mechanism and draw it out:

A
  • Hydride ion from NADH attacks carbonyl carbon of acetaldehyde
67
Q

Two types controls for metabolic reactions and when they occur:

A

Substrate limited : When concentrations of reactant and products in the cell are NEAR EQUILIBRIUM, then it is the availability of substrate which decides the rate of reaction

68
Q

Which reactions are the ones which control the flux of the overall pathway.

A

Enzyme-limited controlled reactions.

69
Q

There are three steps in glycolysis that have enzymes which regulate the flux of glycolysis:

A

I.The hexokinase (HK)

70
Q

Most important enzyme regulating flux of glycolysis is ________

A

PFK-1

71
Q

Regulation of PFK-1:

A
  • Inhibitors –> ATP and citrate
72
Q

How does adenylate kinase work to regulate PFK?

A

It converts 2 ADP molecules to ATP and AMP. in Jǐnjí qíngkuàng, we need a lot of ATP so get that by converting ADP to ATP and AMP, so that AMP can inhibit phosphatase and activate PFK-1.

73
Q

Does ATP slow down PFK-1 activity or block it?

A

slows it down!

74
Q

What is the substrate cycle/futile cycle?

A

In order to control the flux of glycolysis and to have better regulation, cells have FBPase which keeps degrading the product of PFK reaction (FBP) to its substrate (F-6-P). This is called substrate cycle.

75
Q

Why is it considered futile?

A

This is a futile exercise where, cells invest an ATP to produce FBP which is hydrolysed back to F6-P by FBPase. This is a price cells pay to keep glycolysis in check.

76
Q

How is it not really futile tho?

A

Keeps cycles in check and the regulation by AMP allows for a very fast ATP production in emergency situation. This is because AMP activates PFK-1 10 fold while it also inhibits FBPase 10 fold, meaning 100-fold activation to form more ATP in jinji qingkuang.

77
Q

How is hexokinase and glucokinase regulated?

A

It is allosterically inhibited by its product Glucose 6 phosphate. In liver Glucokinase is inhibited by Fructose 6 Phosphate. Uncomplexed ATP acts as a competitive inhibitor of this enzyme.

78
Q

How is pyruvate kinase regulated?

A

It is allosterically inhibited by ATP. ATP binding to the inhibitor site of pyruvate kinase decreases its ability to bring to phosphoenol pyruvate (PEP) the substrate.

79
Q

Glycolysis from glycogen is actually a net 3 ATP. Why?

A

because it enters the pathway as G6P without having to use ATP to phosphorylate.

Metabolism (14 decks)

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