1,3-bisphosphoglycerate (1,3-BPG) is a high-energy, two-phosphate intermediate of glycolysis formed from glyceraldehyde-3-phosphate. Because its phosphate has a higher transfer potential than ATP, it can directly donate a phosphate to ADP, making ATP through substrate-level phosphorylation.
1,3-bisphosphoglycerate (often written 1,3-BPG) is a three-carbon molecule that shows up in the middle of glycolysis, the pathway that breaks glucose down in the cytoplasm. It forms when the enzyme glyceraldehyde-3-phosphate dehydrogenase takes glyceraldehyde-3-phosphate and does two things at once: it oxidizes the molecule (passing electrons to NAD+ to make NADH) and attaches a second phosphate group. The result is a molecule carrying two phosphates, which is where the "bis" in the name comes from.
What makes 1,3-BPG special is that it's a "high-energy" intermediate. The bond holding its top phosphate is unstable and packed with transfer potential, even higher than the phosphate bonds in ATP. That instability is exactly the point: in the next step, 1,3-BPG hands that phosphate straight to ADP, creating ATP and leaving behind 3-phosphoglycerate. So 1,3-BPG is basically a loaded spring that the cell uses to pay back energy.
1,3-BPG lives in topic 7.2 Glycolysis, the first stage of cellular respiration. Glycolysis is split into an energy investment phase (where the cell spends ATP) and an energy payoff phase (where it gets ATP back), and 1,3-BPG is the molecule that kicks off the payoff. Its conversion to 3-phosphoglycerate is one of the two ATP-generating steps in glycolysis, so without 1,3-BPG, the whole pathway wouldn't turn a profit.
It also ties together two big themes in General Biology I: energy capture and redox balance. The same reaction that builds 1,3-BPG also reduces NAD+ to NADH, so this single step shows how cells link making energy carriers to managing electron flow. Understanding it helps you see why glycolysis produces both ATP and NADH.
Keep studying General Biology I Unit 7
Visual cheatsheet
view galleryGlyceraldehyde-3-phosphate (Unit 7)
G3P is the molecule that becomes 1,3-BPG. The enzyme oxidizes G3P and slaps on a phosphate, capturing energy from that oxidation in the new high-energy bond.
3-Phosphoglycerate (Unit 7)
This is what's left after 1,3-BPG donates its phosphate to ADP. That phosphate transfer is the substrate-level phosphorylation step that produces the first ATP of the payoff phase.
ATP (Unit 7)
1,3-BPG has higher phosphate transfer potential than ATP, which is why it can directly phosphorylate ADP and make ATP without needing oxygen or the electron transport chain.
Energy Payoff Phase (Unit 7)
1,3-BPG is the first molecule of the payoff phase, marking the switch from spending ATP to earning it back during glycolysis.
On General Biology I quizzes and exams, 1,3-BPG usually appears in questions about the steps and energetics of glycolysis. You might be asked to identify where in the pathway it forms, name the enzyme involved (glyceraldehyde-3-phosphate dehydrogenase), or explain why this step both makes NADH and sets up ATP production. Short-answer questions often ask you to describe substrate-level phosphorylation, and 1,3-BPG is the textbook example: it donates a phosphate directly to ADP. On diagram-based problems, expect to trace the carbon flow from G3P to 1,3-BPG to 3-phosphoglycerate and explain what's gained at each step.
1,3-BPG has two phosphate groups and is the high-energy molecule before ATP is made; 3-phosphoglycerate is the lower-energy product left over after 1,3-BPG gives one phosphate to ADP. The transition between them is what generates ATP.
1,3-bisphosphoglycerate forms when glyceraldehyde-3-phosphate dehydrogenase oxidizes G3P and adds a second phosphate.
The same reaction that makes 1,3-BPG also reduces NAD+ to NADH, linking energy capture to redox balance.
1,3-BPG has higher phosphate transfer potential than ATP, so it can directly phosphorylate ADP to make ATP.
Converting 1,3-BPG to 3-phosphoglycerate is a substrate-level phosphorylation step and produces the first ATP of the energy payoff phase.
1,3-BPG carries two phosphate groups, which is why the name uses 'bis' (bisphosphate).
It's a high-energy, three-carbon intermediate with two phosphate groups, formed from glyceraldehyde-3-phosphate during glycolysis. It donates a phosphate to ADP to make ATP, kicking off the energy payoff phase.
No. Forming 1,3-BPG produces NADH, not ATP. The ATP comes one step later, when 1,3-BPG transfers a phosphate to ADP and becomes 3-phosphoglycerate.
1,3-BPG carries two phosphates and high energy; 3-phosphoglycerate is the lower-energy product made after 1,3-BPG gives up one phosphate to make ATP. They're consecutive steps in glycolysis.
Glyceraldehyde-3-phosphate dehydrogenase converts glyceraldehyde-3-phosphate into 1,3-BPG, oxidizing it and reducing NAD+ to NADH in the process.
Its top phosphate bond has a higher transfer potential than the phosphate bonds in ATP, so the molecule readily donates that phosphate to ADP, which is why it can drive ATP synthesis.