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Metabolism And Its Control > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

Define glycolysis.

A

Catabolism of glucose to yield two molecules of pyruvate.

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2
Q

Glucose + _______ + _______ + 2Pi

_______ + 2NADH + _______ + _______ + 2H+

A

Glucose + 2NAD+ + 2ADP + 2Pi

2 pyruvate + 2NADH + 2ATP + 2H2O + 2H+

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3
Q

Where does glycolysis take place?

A

In the cytosol.

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4
Q

How many reaction stages are there in glycolysis?

A

10.

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5
Q

What is reaction stage 1 and 2 known as?

A

Energy investment phase.

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6
Q

What is reaction stage 3 known as?

A

Energy harvesting phase.

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7
Q

What tissue does GLUT1 and GLUT3 diffuse across?

A

All mammalian tissues.

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8
Q

What tissue does GLUT2 diffuse across?

A

Liver and pancreatic cells.

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9
Q

What tissue does GLUT4 diffuse across?

A

Muscle and fat cells.

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10
Q

What tissue does GLUT5 diffuse across?

A

Small intestine.

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11
Q

In regards to glucose transport into cells, define isoform specificity.

A

Different affinities for glucose.

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12
Q

How many molecules of ATP are used in glycolysis?

A

Two.

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13
Q

State the three chemical reactions that take place in reaction stage 1 of glycolysis.

A
  1. Glucose —> Glucose-6-phosphate.
  2. Glucose-6-phosphate —> Fructose-6-phosphate.
  3. Fructose-6-phosphate —> Fructose-1,6-bisphosphate.
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14
Q

State the two chemical reactions that take place in reaction stage 2 of glycolysis.

A
  1. Fructose-1,6-bisphosphate —> Glyceraldehyde 3-phosphate + Dihydroxyacetone phosphate.
  2. Dihydroxyacetone phosphate —> Glyceraldehyde 3-phosphate.
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15
Q

Define preparatory phase.

A

Phosphorylation of glucose and its conversion to glyceraldehyde 3-phosphate.

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16
Q

What enzyme is used for the conversion of glucose to glucose-6-phosphate?

A

Glucokinase.

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17
Q

State the coupled reaction of glucose to glucose-6-phosphate.

A

Glucose + ATP —> Glucose-6-phosphate + ADP

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18
Q

State the process that occurs in reaction stage 1 of glycolysis.

A

There is a transfer of phosphoryl group from ATP to glucose. Hexokinase is used but requires Mg2+ ATP complex.

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19
Q

What complex does hexokinase require for essential kinase activity?

A

Mg2+ ATP complex.

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20
Q

What effect does glucose have upon hexokinase?

A

It induces a conformational change in hexokinase by placing ATP close to group C6 in glucose and excludes water from the active site.

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21
Q

What type of group transfer does hexokinase permit?

A

Phosphoryl group transfer.

22
Q

What is the purpose of glucokinase?

A

Localisation.

23
Q

What are two advantages of phosphorylating glucose?

A
  1. Retention in the cell (glucose-6-phosphate cannot easily cross the plasma membrane).
  2. Glucose-6-phosphate is the branch point for several metabolic pathways.
24
Q

State the process that occurs in reaction stage 2 of glycolysis.

A

Glucose-6-phosphate is converted to fructose-6-phosphate by phosphoglucose isomerase. The isomerisation is of an aldose to a ketose and is a readily reversible reaction.

25
Q

State the process that occurs in reaction stage 3 of glycolysis.

A

Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate. Phosphofructokinase (PFK) catalyses this reaction and requires Mg2+ ATP complex.

26
Q

What is the purpose of phosphofructokinase (PFK)?

A

It is the central role in the control of glycolysis (rate determining step).

27
Q

What is reaction stage 4 of glycolysis catalysed by?

A

Aldolase.

28
Q

State the process that occurs in reaction stage 4 of glycolysis.

A

The cleavage of fructose-1,6-bisphosphate forms 2 trioses.

29
Q

What 2 trioses are formed in reaction stage 4 of glycolysis?

A
  1. Glyceraldehyde-3-phosphate (GA3P).

2. Dihydroxyacetone phosphate (DHAP).

30
Q

Out of the 2 trioses formed in reaction stage of glycolysis, which one continues along the glycolytic pathway? What is this known as?

A

Glyceraldehyde-3-phosphate (GA3P). It is known as the suction effect.

31
Q

State the process that occurs in reaction stage 5 of glycolysis.

A

Glyceraldehyde-3-phosphate (GA3P) and dihydroxyacetone phosphate (DHAP) are interconverted by triose phosphate isomerase. Under steady state, as GA3P is consumed, more DHAP is converted into GA3P.

32
Q

What are two outcomes of reaction stages 1 to 5 of glycolysis?

A
  1. Glucose is phosphorylated, consuming 2 ATP.

2. 2x glyceraldehyde-3-phosphate (GA3P) are produced.

33
Q

State the chemical reaction that takes place in reaction stage 6 of glycolysis.

A

Glyceraldehyde-3-phosphate —> 1,3-bisphosphoglycerate

34
Q

State the chemical reaction that takes place in reaction stage 7 of glycolysis.

A

1,3-bisphosphoglycerate —> 3-phosphoglycerate

35
Q

State the chemical reaction that takes place in reaction stage 8 of glycolysis.

A

3-phosphoglycerate —> 2-phosphoglycerate

36
Q

State the chemical reaction that takes place in reaction stage 9 of glycolysis.

A

2-phosphoglycerate —> phosphoenolpyruvate

37
Q

State the chemical reaction that takes place in reaction stage 10 of glycolysis.

A

Phosphoenolpyruvate —> pyruvate

38
Q

What products are produced at the end of glycolysis?

A

2x pyruvate, 2ATP (4ATP are made but 2ATP are consumed) and 2NADH.

39
Q

State the process that occurs in reaction stage 6 of glycolysis.

A

Glyceraldehyde-3-phosphate is oxidised and phosphorylated. It requires co-enzyme NAD+ and Pi, which is catalysed by GAPDH. 1,3-bisphosphoglycerate is produced.

40
Q

What reaction stage in glycolysis is the first high energy intermediate?

A

Reaction stage 6.

41
Q

What does NAD stand for?

A

Nicotinamide adenine dinucleotide.

42
Q

State the process that occurs in reaction stage 7 of glycolysis.

A

3-phosphoglycerate is produced by the catalysation of phosphoglycerate kinase. The first ATP is generated.

43
Q

What reaction stage in glycolysis produces the initial 2 ATP?

A

Reaction stage 7.

44
Q

State the process that occurs in reaction stage 8 of glycolysis.

A

Phosphoglycerate mutase interconverts 3-phosphoglycerate and 2-phosphoglycerate. Mutase forms a 3PG-phosphoenzyme complex which decomposes to form 2PG and regenerate free mutase.

45
Q

State the process that occurs in reaction stage 9 of glycolysis.

A

Enolase forms the second high energy intermediate, phosphoenolpyruvate (PEP). 2PG is dehydrated to PEP by enolase.

46
Q

State the process that occurs in reaction stage 10 of glycolysis.

A

Pyruvate kinase generates the second lot of 2ATP by coupling PEP cleavage to ATP synthesis. Pyruvate kinase requires Mg2+ and K+.

47
Q

Why can glycolysis occur under anaerobic conditions?

A

Because ATP is produced by substrate-level phosphorylation.

48
Q

What are the three irreversible reaction stages of glycolysis.

A

1, 3 and 10.

49
Q

Low ATP levels initiate glycolysis by stimulating what molecule?

A

Phosphofructokinase (PFK).

50
Q

Glucose-6-phosphate can only be made and used in what pathway?

A

The pentose phosphate pathway.

51
Q

What is the effect of glucose-6-phosphatase upon glucose-6-phosphate in the liver and kidneys?

A

It removes the phosphate group, liberating free glucose into the blood.

Metabolism And Its Control (20 decks)

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