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[Biochemistry](https://durgical.com/en/biochemistry/) · Molecule

# Citrate

Citrate is the first molecule of the Krebs cycle; it also carries acetyl to the cytosol to make fat and slows glycolysis when energy is plentiful.

Updated 2026-10-31

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## Key facts

- A six-carbon tricarboxylic acid: citrate synthase makes it from acetyl-CoA and oxaloacetate.
- Outside the mitochondria, ATP-citrate lyase splits it back into acetyl-CoA for fatty acid synthesis.
- It inhibits PFK-1 and activates acetyl-CoA carboxylase.

**Also called**
Citric acid

**Formula**
C₆H₈O₇

**PubChem**
[CID 311](https://pubchem.ncbi.nlm.nih.gov/compound/311)

## Structure

- It is symmetric, yet aconitase treats it as asymmetric: the two carbons that enter as acetyl do not leave as CO₂ in that turn.

## Clinical notes

- Citrate binds calcium: that is why it anticoagulates stored blood, and too much in massive transfusions lowers ionised calcium.
- In urine, citrate prevents calcium stones; potassium citrate is used to prevent them.

## Pathways

- [Krebs cycle (citric acid cycle)](https://durgical.com/en/biochemistry/pathways/krebs-cycle/)
- [Ethanol metabolism](https://durgical.com/en/biochemistry/pathways/ethanol-metabolism/)

## Related conditions

- [Fluoroacetate poisoning](https://durgical.com/en/conditions/fluoroacetate-poisoning/)

## Related

- [Citrate synthase](https://durgical.com/en/biochemistry/enzymes/citrate-synthase/)
- [Acetyl-CoA](https://durgical.com/en/biochemistry/molecules/acetyl-coa/)
- [Phosphofructokinase-1 (PFK-1)](https://durgical.com/en/biochemistry/enzymes/phosphofructokinase-1/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which glycolysis enzyme does citrate inhibit?

Phosphofructokinase-1.

## Why does citrate anticoagulate banked blood?

It chelates calcium, which clotting needs.

## How does acetyl-CoA leave the mitochondria to make fat?

As citrate; in the cytosol ATP-citrate lyase releases the acetyl-CoA.

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Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Citric acid (CID 311)](https://pubchem.ncbi.nlm.nih.gov/compound/311) (PubChem, NCBI, 2026) · Public domain; [Citric acid cycle (TCA cycle)](https://reactome.org/PathwayBrowser/#/R-HSA-71403) (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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