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BCM210 > Topic 11 - Glycolysis & Gluconeogenesis > Flashcards

Topic 11 - Glycolysis & Gluconeogenesis Flashcards

1
Q
A
  1. 2800 kJ/mol
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2
Q
A
  1. 10
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3
Q

Define Glycolysis (not detail of steps just basic over view)

A
  • Involves degradation (catabolism) of glucose (6C) to 2 pyruvate (3C)
  • Occurs in 10 steps:
    -1st 5 preparatory phase =>cost 2 ATP
    glucose phosphorylated twice & split in two
    products isomerised to yield two glyceraldehyde 3P (3C)

-2nd 5 pay off phase => yields 4 ATP & 2 NADH
2 glyceraldehyde 3P oxidised to 2 pyruvate
* Net yield: 2 ATP & 2 NADH

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4
Q

Write out the net equation of Glycolysis

A

Glucose + 2NAD+ + 2ADP + 2Pi

=>

2 Pyruvate + 2NADH + 2ATP + 2H+ + 2H2O

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5
Q

1 glucose molecule under anaerobic conditions produces …. ATP by ………
Using either ………… fermentation or ………… fermentation

A

1 glucose molecule under anaerobic conditions produces 2 ATP by substrate-level phosphorylation

Using either lactic acid fermentation or alcohol fermentation

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6
Q

1 glucose molecule under aerobic conditions produces …….. ATP by ……………… & ……………….

A

1 glucose molecule under aerobioc conditions produces 30-32 ATP by substrate-level phosphorylation & oxidative phosphorylation

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7
Q

Steps of Glycolysis

Describe step 1 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Priming step - glucose is phosphorylated

  • Reaction is irreversible
  • Costs 1 ATP
  • Phosphorylation rxn
  • Hexokinase catalyses transfer of terminal phosphoryl group of ATP => glucose
  • requires Mg2+ cofactor
  • Hexokinase activity < when [glucose] < & vice versa
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8
Q

Steps of Glycolysis

Describe step 2 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Conversion of glucose 6P to fructose 6P

  • Reaction is reversible
  • Isomerisation of glucose 6P (aldose) to fructose 6P (ketose) by phosphohexose isomerase
  • requires Mg2+<em> </em>cofactor
  • 6 member ring => 5 member ring
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9
Q

Steps of Glycolysis

Describe step 3 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

2nd priming step -another phosphate added

  • Rate-limiting step!! => major control point
  • Reaction is irreversible
  • Phosphorylation
  • Costs 1 ATP
  • PFK-1 catalyses transfer of terminal phosphoryl group of ATP to fructose 6P producing F 1,6 BP
  • requires Mg2+ cofactor
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10
Q

Steps of Glycolysis

Describe step 4 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Cleavage of fructose 1,6 BP

  • Reaction is reversible
  • Aldolase splits F1,6BP into two triose sugars:
  • dihydroxyacetone P
  • glyceraldehyde 3P
  • Overall ∆G˚ = approx. 0
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11
Q

Steps of Glycolysis

Describe step 5 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Interconversion of triose phosphates

  • Isomerisation
  • Only glyceraldehyde is directly utilised by subsequent glycolysis steps
  • Dihydroxyacetone P is converted to glyceraldehyde 3P by triose phosphate isomerase
  • Thus, 1 glucose molecule has been converted to two glyceraldehyde 3P
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12
Q

Steps of Glycolysis

Describe step 6 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Addition of phosphate to glyceraldehyde 3P

  • REDOX
  • 2 NADH produced
  • Energy conserving
  • Oxidation (loss H+) => energy conserved in acyl phosphate
  • H atom removed from each substrate, accepted by NAD+ to become NADH (reduced -gain H)
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13
Q

Steps of Glycolysis

Describe step 7 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

ATP regeneration

  • Substrate-level phosphorylation!!!
  • 2 ATP produced
  • Phosphoglycerate kinase transfers high e phosphoryl group from 1,3BP-glycerate to ADP forming ATP & 3-phosphoglycerate.
    =>coupled w/ step 6
  • SLP: formation of ATP by transfer of a phosphoryl group from a high e substrate
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14
Q

Steps of Glycolysis

Describe step 8 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Isomerisation of 3-phosphoglycerate

  • Reaction is reversible
  • Phosphoglycerate mutase transfers phosphoryl group b/w C2 and C3 of glycerate
  • requires Mg2+ cofactor
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15
Q

Steps of Glycolysis

Describe step 9 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

Dehydration

  • Reaction is reversible
  • Enolase catalyses removal of water from 2-phosphoglycerate, forming phosphoenolpyruvate (PEP)
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16
Q

Steps of Glycolysis

Describe step 10 of glycolysis

  • defining character of step?
  • what kind of reaction?
  • what enzymes are used?
A

3rd irreversible step

  • Substrate-level phosphorylation!!!
  • Reaction is irreversible
  • 2 ATP produced
  • Pyruvate kinase transfers phosphoryl group from PEP to ADP, forming pyruvate & ATP
  • requires K+ & Mg2+ cofactors
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17
Q

Draw a flow chart giving the brief details of glycolysis

-try to include enzymes

18
Q

Write out the equation (stoichiometry) for the glycolytic pathway in relation to ATP production & electron balance

19
Q

Metabolic fates of Pyruvate

Under aerobic conditions?

A

Pyruvate converted to acetyl-CoA & completely oxidised to CO2 and H2O

20
Q

Metabolic fates of Pyruvate

Under anaerobic conditions?

A

Pyruvate NOT fully oxidised to CO2 and H2O
=> converted to either lactate or ethanol

21
Q

Metabolic fates of pyruvate
Describe lactic acid fermentation

A
  • Low oxygen, pyru reduced to lactate, NADH oxidised to NAD+ to replenish NAD+ stores :: allowing glycolysis to continue
  • Conversion of pyru => lactate produces 2NAD+
22
Q

Metabolic fates of pyruvate
Describe alcohol fermentation

A

Yeast ferments glucose to ethanol & CO2

    1. Decarboxylation of pyru to acetaldehyde by pyru decarboxylase
    1. Reduction of acetaldehyde to ethanol by alcohol dehydrogenase
23
Q

Gluconeogenesis

  1. What is it?
  2. When does it occur?
  3. Why does it occur?
  4. How does it occur (in brief)?
A
  1. What? Synthesis of glucose from pyru & other 3C/4C compounds
  2. When? Blood glucose levels <
  3. Why? Maintains BG levels, control of acid/base balance, removal of lactate (CORI cycle), vital for brain
  4. -almost reverse of glycolysis.
    - energy expensive
    - differs from glycolysis at 3 irreversible steps (1, 3, 10) => bypasses these
24
Q

Gluconeogenesis

Describe 1st bypass step

A

Last step of glycolysis (10)

  • Pyruvate converted to PEP
    *
25
Q

Gluconeogenesis

Describe 2nd bypass step

A

Step 3 of glycolysis

  • Conversion of fructose 1,6bisphos. to fructose 6P
    => does not require ATP unlike glycolysis step
  • ∆G˚ = -16.3 kJ/mol
26
Q

Gluconeogenesis

Describe 3rd bypass step

A

Step 1 of glycolysis

  • Conversion of glucose 6P to glucose
    *
27
Q

Write the overall GNG equation

28
Q

What is the cost and yield of:
Glycolysis?
GNG?

A

Glycolysis:
Cost = 2 ATP
makes = 4 ATP
Net yield = 2 ATP, 2 NADH

GNG:

Cost = 6 ATP
Yield =glucose

29
Q

Briefly describe the CORI cycle

(use diagram if needed)

A

Cycling of lactate produced by anaerobic glycolysis through the liver => blood. In liver it is converted to pyru by lactate dehydrogenase. Pyru is then cycled back into glucose by glycogenesis => blood.

30
Q

Briefly describe the Pentose Phosphate Pathway

A

PPP is an alternative pathway of glucose catabolism
Main function is to synthesis:

  • NADPH for FA synth.
  • Ribose-5-phosphate for nucleic acid synth.

PPP is most active in:

  • dividing cells
  • adipose tissue
  • RBC’s
31
Q
A
  1. Phosphofructokinase-1
32
Q
A
  1. Reactions 7 and 10
33
Q
A
  1. Reaction 6
34
Q
A
  1. None of the above (2mol ATP & 2mol NADH)
35
Q
A
  1. 2 mol of ATP
36
Q
A
  1. 3-phosphoglycerate kinase
37
Q
A
  1. It consists entirely of the reactions of glycolysis, operating in the reverse direction
38
Q
A
  1. Phosphofructokinase-1 (only in glycolysis)
39
Q
A
  1. Supply pentoses and NADPH
40
Q
A

Pyruvate => lactate

41
Q
A
  1. Produces more energy (in the form of ATP) than aerobic respiration

BCM210 (18 decks)

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