Glycolysis First 5 Steps

Question 1

Step 1

Hexokinase

Answer 1

Converts GLUCOSE + ATP to GLUCOSE-6-PHOSPHATE + ADP
Irreversible reaction
Invest ATP
Hexokinase is a transferase that phosphorylates (adds or transfers a phosphate group or molecule)
GLUCOSE-6-PHOSPHATE is a competitive inhibitor

Question 2

Step 2

Phosphoglucose isomerase

Answer 2

Converts GLUCOSE-6-PHOSPHATE to FRUCTOSE-6-PHOSPHATE
Reversible reaction
Fructose is a six-carbon ketose that forms a five-membered ring
Reaction is near equilibrium
Glucose-6-phosphate is aldose and Fructose-6-phosphate is a ketose

Question 3

Step 3

Phosphofructokinase

Answer 3

Converts FRUCTOSE-6-PHOSPHATE + ATP to FRUCTOSE-1,6-BISPHOSPHATE + ADP
Irreversible reaction
ATP is invested and drives the reaction.
Phosphofructokinase is a transferase
Glycolysis is regulated at this step; unique for glycolysis. Rate limiting step.
Fructose 1,6-bis p is a feed forward regulation and can written linear or cyclical.

Question 4

Step 4

Aldolase

Answer 4

Converts FRUCTOSE-1,6-BISPHOSPHATE to GLYCERALDEHYDE-3-PHOSPHATE + DIHYDROXYACETONE PHOSPHATE
Reversible reaction
Aldolase is a lyase (cleaves to make the 2 molecules)
Rapid consumption

Question 5

Step 5

Triose phosphate isomerase

Answer 5

Converts DIHYDROXYACETONE PHOSPHATE to GLYCERALDEHYDE-3-PHOSPHATE
Isomerization reaction (moves a group or a double bond within the same molecule)
Reversible reaction
Can convert back and forth
GAP is quickly consumed
2 GAP’s proceed through remainder of glycolysis