MBBS · Biochemistry

Citric acid cycle

The citric acid cycle oxidizes acetyl units in the mitochondrial matrix while transferring electrons to NADH and FADH₂ and producing a nucleoside triphosphate equivalent.

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Citric acid cycle — learning map

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LABELED RELATIONSHIP MAP · SCHEMATIC, NOT TO SCALEEntry and condensationacetyl-CoA + oxaloacetateOxidative stepsreduced coenzymesSubstrate-level phosphorylationone GTP equivalentIntermediates as building blocksanaplerosisCitric acid cycleKEY RELATIONSHIPS

Original schematic relationship map for this topic; relationships are organized for study, not intended as an anatomical depiction or a diagnostic algorithm.

Concept 01

Entry and condensation

Acetyl-CoA condenses with oxaloacetate to form citrate, initiating a cycle that ultimately regenerates oxaloacetate.

Concept 02

Oxidative steps

One acetyl-CoA turn generally produces three NADH and one FADH₂ through enzyme-catalyzed oxidations.

Concept 03

Substrate-level phosphorylation

The succinyl-CoA synthetase reaction produces a nucleoside triphosphate, often presented as GTP in textbook accounting.

Concept 04

Intermediates as building blocks

Cycle intermediates can be withdrawn for biosynthesis and replenished through anaplerotic reactions; pathway function depends on linked respiration.

Education / safety note: The cycle does not directly use molecular oxygen, but sustained oxidative activity depends on respiratory reoxidation of its reduced cofactors.

Reference and next reading

Explore the original curriculum and publisher-hosted resources for full-depth reading; this note is an original schematic introduction, not an exhaustive chapter.

Official / publisher source: NMC official CBME Curriculum 2024 and current regulations index ↗Official / publisher source: NCBI Bookshelf ↗Official / publisher source: PubMed ↗