Glycolysis - 4.2

Q: What is the purpose of glycolysis?

A: It is the first set of reactions for extracting energy from sugar.

Q: Where does glycolysis occur?

A: In the cytosol of the cell.

Q: How many steps does glycolysis have?

10 steps

Q: What are the two phases of glycolysis?

A: Energy investment phase and energy payoff phase.

Q: What happens in the energy investment phase?

A: Energy is released (ADP + Pi).

Q: What happens in the energy payoff phase?

A: Energy is produced (ATP and NADH).

Q: What happens to glucose in step 1?

A: Glucose receives a phosphate group from ATP and becomes glucose-6-phosphate.

• Herokinase -  Enzyme that catalyzes the step  

Q: What happens to glucose-6-phosphate in step 2?

A: It is rearranged into its isomer, fructose-6-phosphate.

• Phosphoglucoisomerase.

Q: What happens in step 3?

A: Fructose-6-phosphate receives a phosphate from ATP, becoming fructose-1,6-bisphosphate.

• Phosphofructokinase.

• 2 ATPs have been used so far

Q: What happens in step 4?

A: Fructose-1,6-bisphosphate is split into two molecules: Glyceraldehyde-3-phosphate (G3P) and Dihydroxyacetone phosphate (DHAP).

• Aldolase

Q: What happens to DHAP in step 5?

A: DHAP is converted to G3P through an isomerization reaction.

• isomerase.

• Two molecules of G3P proceed to the next step

Q: What happens in step 6?

A: Two electrons and two protons are removed from G3P, forming 1,3-bisphosphoglycerate.

• A: Triosephosphate dehydrogenase.

• 2 NADH moleculea are produced at this stage

Q: What happens to the electrons and protons (s6)?

A: Electrons are accepted by NAD+ to form NADH, and the remaining proton moves to the cytosol.

Q: What happens in step 7?

A: 1,3-bisphosphoglycerate loses a phosphate group, which undergoes substrate-level phosphorylation with ADP to make ATP, forming 3-phosphoglycerate.

• Phosphoglycerate kinase.

Q: How many ATPs are produced at this stage?
A: 2 ATPs.

Q: What happens in step 8?

A: 3-phosphoglycerate rearranges its phosphate group from carbon-3 to carbon-2, forming 2-phosphoglycerate.

Q: Which enzyme catalyzes step 8?
A: Phosphoglucomutase.

Q: What happens in step 9?

A: Electrons are removed from 2-phosphoglycerate, water is lost, and phosphoenolpyruvate (PEP) is produced.

• Enolase.

  Q: How many H₂O molecules are produced at this stage?
  A: 2 H₂O.

Q: What happens in step 10?

A: PEP loses a phosphate group, which undergoes substrate-level phosphorylation with ADP to produce ATP, forming pyruvate

• Pyruvate kinase.

Q: How many ATPs are produced at this stage?

A: 2 ATPs.

Q: What is the net total production at the end of glycolysis?

A: 2 ATP, 2 NADH, 2 H₂O, 2 H⁺.

Q: For every one mole of glucose, what percentage is converted to ATP?

A: 2.2%.

The net formula for glycolysis

Glucose+2ADP+2Pi+2NAD+⟶2Pyruvate+2ATP+2NADH+ 2H+2H2​O