Glycolysis

Question 0

True commitment step

Primary regulatory site

Answer 0

6-phosphofructo-1-kinase (PFK1)

Fructose 6-phosphate->Fructose 1,6-bisphosphate (ATP->ADP)

Question 1

Enzyme that traps glucose in the cell

Answer 1

Hexokinase

Question 2

Hexokinase

Answer 2

Mg2+ is a cofactors, bound to ATP commits glucose to metabolic pathway, traps glucose in cell

Question 3

Aldolase

Answer 3

Fructose 1,6-biphosphate->dihydroxyacetone phosphate (DHAP) + glyceraldehyde 3-phosphate (GAP)

Convert DHAP ->GAP via triose phosphate isomerase

Question 4

1st substrate level phosphorylation:
Coupled rxns/enzymes
Common intermediate

Answer 4

Coupled rxns/enzymes:

1) glyceraldehyde 3-phosphate dehydrogenase
2) 3-phosphoglycerate kinase

Intermediate: 1,3 bisphosphoglycerate

Question 5

Production of 2,3 BPG

Answer 5

Erythrocytes have another mutase that converts 1,3-biphosphoglycerate->2,3 BPG

Biphosphoglycerate mutase

Question 6

2nd substrate level phosphorylation
Coupled rxns/enzymes
Common intermediate

Answer 6

Coupled rxns/enzymes

1) Enolase
2) Pyruvate Kinase

Intermediate: phosphoenolpyruvate (PEP)

Question 7

Why is ATP production decreased in PK deficiency?

Answer 7

PK catalyzes one of the ATP-producing rxns of glycolysis (2nd substrate level phosphorylation)

Question 8

Why might ATP synthesis from glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase be inhibited by PK deficiency?

Answer 8

No PK->Pyruvate can’t be produced->no way in the RBC to re-ox NADH generated in the glyceraldehyde-3-phosphate dehydrogenase rxn because they lack mitochondria, thus can’t generate 1,3-biphosphoglycerate

Question 9

Why are RBC especially vulnerable to the reduction in ATP from glycolysis?

Answer 9

RBC lack mitochondria->Pyruvate is reduced to lactate (anaerobic glycolysis) which enters plasma
RBC unable to completely oxidized glucose to CO2+H2O, and so are dependent on glycolysis for ATP production

Question 10

In PK deficiency, levels of 2,3-BPG may increase three-fold. Why?

Answer 10

Build up in substrate makes minor pathways into major ones
PK->buildup of PEP
Reversible rxns going backwards:
Enolase
Phosphoglycerate mutase
3-

Question 11

10 enzymes of aerobic glycolysis

Answer 11

Hexokinase
Phosphoglucose isomerase
PFK-1
Aldolase
Triose phosphate isomerase
Glyceraldehyde 3-phosphate dehydrogenase
3-phosphoglycerate kinase
Phosphoglycerate mutase
Enolase
Pyruvate kinase*

Question 12

Enzyme special to anaerobic tissue glycolysis.

What does it do?

Answer 12

Lactate dehydrogenase
Reduces: Pyruvate->lactate
Oxidizes: NADH->NAD
Anaerobic tissues lack mitochondria, thus need different way of re-oxidizing NADH to continue the cycle

Question 13

Pyruvate Kinase Deficiency

Answer 13

Not really a deficiency->mutation
Increased Km=lower affinity for its substrate PEP
Premature hemolysis of RBC’s: hemolytic anemia
Amish-auto recessive
Most common enzymopathy of glycolysis

Question 14

Enzymes that catalyze irreversible reactions

Answer 14

Hexokinase
PFK-1/6 phosphofructo-1-kinase
Pyruvate kinase

Question 15

PFK-1

Answer 15

3rd step
2nd irreversible, true commitment step of glycolysis, primary regulatory site
Fructose 6 phosphate-> fructose 1,6-bisphosphate uses one ATP

Question 16

Dehydroxyacetone Phosphate

Answer 16

DHAP
Produced w/GAP from fructose 1,6-bisphosphate by aldolase
Not used in glycolysis
Need triose phosphate isomerase to convert DHAP->GAP

Question 17

Pyruvate Kinase

Answer 17

Last irreversible rxn of aerobic glycolysis

PEP->Pyruvate+ATP

Question 18

Substrate and Products for aldolase

Answer 18

Substrate:fructose 1,6-bisphosphate

Products : DHAP(ketose) & GAP(aldose)

Question 19

Oxidation of 1 mol glucose to lactate generates a net of _ ATP

Answer 19

2 ATP

Question 20

Substrate level phosphorylation

Answer 20

SLP

synthesis of ATP via 2 coupled reactions involves a high-energy common intermediate

Question 21

Enzyme that generates NADH

Answer 21

Glyceraldehyde 3 phosphate dehydrogenase
(1st SLP)
GAP-> 1,3 bisphosphoglycerate

Question 22

What happens to NADH in aerobic conditions?

Answer 22

NADH is oxidized by a substrate such as oxaloacetate, whose reduced form (malate) can be transported across a mitochondrial membrane

Question 23

In glycolysis one mole of orthophosphate (Pi) is consumed in a reaction catalyzed by what enzyme?

Answer 23

Glyceraldehyde 3-phosphate
Reduces NAD to NADH
First enzyme in first SLP
GAP -> 1,3 bisphosphoglycerate

Question 24

Enzyme that uses ATP

Answer 24

1) Hexokinase
Cosubstrate ATP, Mg2+ is a cofactor bound to ATP
Irreversible, traps glucose as glucose 6-phosphate
2) PFK-1
Irreversible, true commitment step, primary regulatory step
Fructose 6 phosphate + ATP -> fructose 1,6 bisphosphate + ADP