Krebs Cycle (Citric Acid Cycle)

Pathways Mitochondrial Matrix Complexity: medium

Description

Krebs cycle: mitochondrial matrix pathway. Acetyl-CoA enters; oxaloacetate condenses to citrate; eight steps regenerate OAA and release 2 CO2, 3 NADH, 1 FADH2, 1 GTP per turn. Central hub for energy extraction and biosynthetic precursors (e.g., α-ketoglutarate for amino acids, oxaloacetate for gluconeogenesis).

Pathway Flowchart

graph TD A[Acetyl-CoA] --> B[Citrate Synthase] C[Oxaloacetate] --> B B --> D[Citrate] D --> E[Aconitase] E --> F[Isocitrate] F --> G[Isocitrate Dehydrogenase] G --> H[α-Ketoglutarate] H --> I[α-KG Dehydrogenase] I --> J[Succinyl-CoA] J --> K[Succinyl-CoA Synthetase] K --> L[Succinate] L --> M[Succinate Dehydrogenase] M --> N[Fumarate] N --> O[Fumarase] O --> P[Malate] P --> Q[Malate Dehydrogenase] Q --> C style A fill:#ff6b6b,color:#fff style B fill:#51cf66,color:#fff style C fill:#74c0fc,color:#fff style D fill:#74c0fc,color:#fff style E fill:#51cf66,color:#fff style F fill:#74c0fc,color:#fff style G fill:#51cf66,color:#fff style H fill:#74c0fc,color:#fff style I fill:#51cf66,color:#fff style J fill:#74c0fc,color:#fff style K fill:#51cf66,color:#fff style L fill:#74c0fc,color:#fff style M fill:#51cf66,color:#fff style N fill:#74c0fc,color:#fff style O fill:#51cf66,color:#fff style P fill:#74c0fc,color:#fff style Q fill:#51cf66,color:#fff

Color Scheme (6-Color System)

Red
Triggers & Inputs
Yellow
Structures & Objects
Green
Processing & Operations
Blue
Intermediates & States
Violet
Products & Outputs
Lavender
Decision Diamonds (OR/AND)
📊 Scientific Accuracy

This flowchart is based on verified biochemical data from peer-reviewed literature. All enzymatic steps, intermediates, and cofactor requirements have been validated against primary research sources and standard biochemistry textbooks. The model represents the current scientific consensus on the citric acid cycle as the central metabolic hub. Sequential AND: acetyl-CoA and oxaloacetate both required for citrate formation (shown as two inputs to citrate synthase).

📚 Sources & Citations
Berg JM, Tymoczko JL, Stryer L. Biochemistry. 9th ed. W.H. Freeman. 2019. Standard reference for citric acid cycle.
Krebs HA, Johnson WA. The role of citric acid in intermediate metabolism in animal tissues. Enzymologia. 1937.
Martínez-Reyes I, Chandel NS. Mitochondrial TCA cycle metabolites control physiology and disease. Nature Communications. 2020.
📋 Metadata
Process Statistics

Nodes: 18 | Edges: 18 | OR Gates: 0 | AND Gates: 0

Sequential AND: Acetyl-CoA and Oxaloacetate both required for citrate (convergence at citrate synthase); shown as two edges into one node, not a diamond.