Glycolysis Intermediates in Order and ATP Steps

Glycolysis Intermediates in Order: First Intermediate and Which Steps Make ATP

By StudyStore · Published 2026-11-05 · 1 min read · 233 words

The first intermediate in glycolysis is glucose-6-phosphate, made when hexokinase (or glucokinase in liver) phosphorylates glucose and traps it in the cell.

Intermediates in order

Step	Enzyme	Product	ATP or NADH
1	Hexokinase / glucokinase	Glucose-6-phosphate	Uses 1 ATP
2	Phosphoglucose isomerase	Fructose-6-phosphate
3	PFK-1	Fructose-1,6-bisphosphate	Uses 1 ATP
4	Aldolase	DHAP + glyceraldehyde-3-phosphate
5	Triose phosphate isomerase	Interconverts DHAP and G3P
6	GAPDH	1,3-bisphosphoglycerate	Makes 1 NADH
7	Phosphoglycerate kinase	3-phosphoglycerate	Makes 1 ATP
8	Phosphoglycerate mutase	2-phosphoglycerate
9	Enolase	Phosphoenolpyruvate
10	Pyruvate kinase	Pyruvate	Makes 1 ATP

Steps 6 to 10 run twice per glucose because step 4 yields two three-carbon pieces.

Which steps produce ATP

Steps 7 and 10 make ATP by substrate-level phosphorylation. That is 2 ATP per triose, so 4 ATP per glucose. Steps 1 and 3 spend 2 ATP, so the net is 2 ATP and 2 NADH per glucose.

Irreversible steps

Steps 1, 3 and 10 are the large negative delta G steps and the main control points.

Common traps

Counting 4 ATP as the net. Subtract the 2 invested.
Forgetting that steps 6 to 10 double.
Placing the NADH step with ATP use. NADH is made at GAPDH.

One-minute recap

First intermediate: glucose-6-phosphate.
ATP spent at steps 1 and 3; made at steps 7 and 10.

Check yourself: 5-question mini-quiz

Try each question first, then click it to reveal the answer.

1. What is the first intermediate in glycolysis?

Glucose-6-phosphate.

2. Which two steps consume ATP?

Hexokinase (step 1) and PFK-1 (step 3).

3. Which two steps make ATP?

Phosphoglycerate kinase and pyruvate kinase.

4. Which enzyme produces NADH?

Glyceraldehyde-3-phosphate dehydrogenase.

5. What is the net ATP per glucose?

2 ATP.

Free MCAT sampler

Enter your email and download a real page set from a paid pack: the 3-page Amino Acids, Proteins and Enzymes cheat sheet (PDF). Confirm your email and short MCAT lessons follow. Free, no card.

Prefer not to sign up? The sampler is open to everyone: free notes, practice sets and the study schedule generator.

Written by StudyStore from standard scientific facts. Study aid only. Always check values against the reference your exam provides.