Glycolysis

Question 1

Define glycolysis.

Answer 1

Catabolism of glucose to yield two molecules of pyruvate.

Question 2

Glucose + _______ + _______ + 2Pi

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

Answer 2

Glucose + 2NAD+ + 2ADP + 2Pi

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

Question 3

Where does glycolysis take place?

Answer 3

In the cytosol.

Question 4

How many reaction stages are there in glycolysis?

Answer 4

10.

Question 5

What is reaction stage 1 and 2 known as?

Answer 5

Energy investment phase.

Question 6

What is reaction stage 3 known as?

Answer 6

Energy harvesting phase.

Question 7

What tissue does GLUT1 and GLUT3 diffuse across?

Answer 7

All mammalian tissues.

Question 8

What tissue does GLUT2 diffuse across?

Answer 8

Liver and pancreatic cells.

Question 9

What tissue does GLUT4 diffuse across?

Answer 9

Muscle and fat cells.

Question 10

What tissue does GLUT5 diffuse across?

Answer 10

Small intestine.

Question 11

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

Answer 11

Different affinities for glucose.

Question 12

How many molecules of ATP are used in glycolysis?

Answer 12

Two.

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

Define preparatory phase.

Answer 15

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

Question 16

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

Answer 16

Glucokinase.

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

What complex does hexokinase require for essential kinase activity?

Answer 19

Mg2+ ATP complex.

Question 20

What effect does glucose have upon hexokinase?

Answer 20

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

Question 21

What type of group transfer does hexokinase permit?

Answer 21

Phosphoryl group transfer.

Question 22

What is the purpose of glucokinase?

Answer 22

Localisation.

Question 23

What are two advantages of phosphorylating glucose?

Answer 23

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.

Question 24

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

Answer 24

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.

Question 25

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

Answer 25

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

Question 26

What is the purpose of phosphofructokinase (PFK)?

Answer 26

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

Question 27

What is reaction stage 4 of glycolysis catalysed by?

Answer 27

Aldolase.

Question 28

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

Answer 28

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

Question 29

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

Answer 29

1. Glyceraldehyde-3-phosphate (GA3P). | 2. Dihydroxyacetone phosphate (DHAP).

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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.

Question 32

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

Answer 32

1. Glucose is phosphorylated, consuming 2 ATP. | 2. 2x glyceraldehyde-3-phosphate (GA3P) are produced.

Question 33

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

Answer 33

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

Question 34

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

Answer 34

1,3-bisphosphoglycerate ---> 3-phosphoglycerate

Question 35

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

Answer 35

3-phosphoglycerate ---> 2-phosphoglycerate

Question 36

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

Answer 36

2-phosphoglycerate ---> phosphoenolpyruvate

Question 37

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

Answer 37

Phosphoenolpyruvate ---> pyruvate

Question 38

What products are produced at the end of glycolysis?

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

Reaction stage 6.

Question 41

What does NAD stand for?

Answer 41

Nicotinamide adenine dinucleotide.

Question 42

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

Answer 42

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

Question 43

What reaction stage in glycolysis produces the initial 2 ATP?

Answer 43

Reaction stage 7.

Question 44

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

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

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

Question 47

Why can glycolysis occur under anaerobic conditions?

Answer 47

Because ATP is produced by substrate-level phosphorylation.

Question 48

What are the three irreversible reaction stages of glycolysis.

Answer 48

1, 3 and 10.

Question 49

Low ATP levels initiate glycolysis by stimulating what molecule?

Answer 49

Phosphofructokinase (PFK).

Question 50

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

Answer 50

The pentose phosphate pathway.

Question 51

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

Answer 51

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