Glycolysis Flashcards
What is the overall reaction of glycolysis?
Glucose —-> pyruvate
What are the net products of glycolysis?
- Pyruvate x2
- NADH x2
- ATP x2
What are the two phases of glycolysis?
- Preparation phase (Glucose - G3P)
2. Pay-off phases (1,3-BPG - pyruvate)
What is the significance that G6P is a negatively charged molecule?
It traps glucose within the cell
Reaction 1: what is it?
What does it require?
Glucose —> Glucose-6-phosphate
ATP
Hexokinase
In which form is the ATP used in reaction 1 supplied?
MgATP
Reaction 2: what is it?
What does it require?
Glucose-6-phosphate —-> Fructose-6-phosphate
Phosphoglucose isomerase
Reaction 3: what is it?
What does it require?
Fructose-6-phosphate —> Fructose-1, 6-bisphosphate
Phosphofructokinase-1
Uses ATP
Reaction 4: What is it?
What does it require?
Fructose-1, 6-bisphosphate —-> Glyceraldehyde-3-phophate + Dihydroxyacetone glycerate
Requires aldolase
Reaction 5: What is it?
What does it require?
Dihydroxyacetone glycerate —-> Glyceraldehyde-3-phophate
Requires triose phosphate isomerase
Reaction 6: What is it?
What does it require?
Glyceraldehyde-3-phophate —-> 1, 3-bisphosphoglycerate
Requires glyceraldehyde-3-phosphate dehydrogenase
Produces 2 NADH
Reaction 7: What is it?
What does it require?
1, 3-bisphosphoglycerate —-> 3-phosphoglycerate
Requires phosphoglycerate kinase
Produces 2 ATP
Reaction 8: What is it?
What does it require?
3-phosphoglycerate —-> 2-phosphoglycerate
Requires phosphoglyceromutase
Reaction 9: What is it?
What does it require?
2-phosphoglycerate ——>phosphoenol pyruvate
Requires enolase
Produces H2O
Reaction 10: What is it?
What does it require?
Phosphoenol pyruvate —-> pyruvate
Requires pyruvate kinase
Produces 2 ATP
Which is the only reaction involving ATP that is reversible?
Reaction 7: 1, 3-BPG —> 3-PG
Why is arsenate poisonous?
Practically identical to phosphate so substitutes it meaning a different product is formed and an ATP-producing step is skipped
At which reaction does arsenate substitute phosphate?
At reaction 6 to form 1-arseno-3-phosphoglycerate
In anaerobic conditions, what reaction does pyruvate undergo?
Pyruvate —–> lactate
catalysed by lactate dehydrogenase
produces NAD
At what three points is glycolysis regulated?
- PFK-1
- Hexokinase
- Pyruvate kinase
How is hexokinase regulated?
Regulated by glucose-6-phosphate
Why is regulation at hexokinase not a major point?
Because glucose can also be converted to glycogen
How is pyruvate kinase regulated?
Inhibited by ATP and acetyl CoA
Activated by fructose-1, 6-bisphosphate
What is pyruvate kinase activated by?
Fructose-1, 6-bisphosphate
What is pyruvate kinase inhibited by?
ATP and acetly CoA
How is phosphofructokinase-1 regulated?
Inhibited by ATP
Inhibition is reversed by AMP
How is PFK-1 inhibited?
Inhibited by ATP as at high levels, ATP allosterically inhibits PFK-1 thus lowering the affinity of PFK-1 for fructose-6-phosphate
How is the inhibition of PFK-1 reversed?
Inhibition is reversed by AMP
What is Tarui disease?
A disease that prevents the conversion of fructose-6-phosphate —> fructose-1, 6-phosphate
Give examples of symptoms of Tarui disease?
Muscle fatigue and cramping
How many forms of hexokinase are there?
Four. I to IV
Which forms of hexokinase are known as glucokinase?
I and IV
Where can glucokinase be found?
In hepatocytes
Difference between hexokinase and glucokinase
Hexokinase works at maximum rate at minimum levels of glucose
Glucokinase doesn’t reach maximum rate until [glucose] is much higher
What does glucokinase do?
Helps the liver to buffer blood glucose
Hexokinase II
Molecule in open configuration when no glucose molecule is bound
After binding –> closed configuration
Per glucose molecule, what is the net yield of glycolysis?
2xPyruvate, 2xNADH, 2xATP
