Calvin Cycle (Light-Independent Reactions)

Pathways Chloroplast Stroma Complexity: medium

Description

Calvin cycle: stroma of chloroplasts. Fixes CO2 into organic carbon using ATP and NADPH from light reactions. Three phases: carboxylation (RuBisCO fixes CO2 onto RuBP), reduction (3-PGA → G3P), regeneration of RuBP. Produces 3-carbon sugars (G3P) for biosynthesis; some G3P exits for sucrose/starch synthesis.

Pathway Flowchart

graph TD A[CO2] --> B[RuBisCO] C[RuBP] --> B B --> D[3-PGA] D --> E[3-PGA Kinase] E --> F[1,3-BPG] G[NADPH] --> F F --> H[GAP Dehydrogenase] H --> I[G3P] I --> J{Output or Regenerate?} J -->|Regenerate| K[Transketolase / Aldolase] K --> L[Various Intermediates] L --> M[Ru5P Kinase] N[ATP] --> M M --> C J -->|Output| O[Sucrose / Starch] style A fill:#ff6b6b,color:#fff style G fill:#ff6b6b,color:#fff style N 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 H fill:#51cf66,color:#fff style I fill:#74c0fc,color:#fff style J fill:#b4b4dc,color:#000 style K fill:#51cf66,color:#fff style L fill:#74c0fc,color:#fff style M fill:#51cf66,color:#fff style O fill:#b197fc,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. The model represents the current scientific consensus on the Calvin–Benson–Bassham cycle. The OR gate represents the branch point: G3P can either regenerate RuBP (cycle continues) or exit as product (sucrose, starch).

📚 Sources & Citations
Bassham JA, Benson AA, Calvin M. The path of carbon in photosynthesis. Journal of Biological Chemistry. 1950.
Ellis RJ. The most abundant protein in the world. Trends in Biochemical Sciences. 1979.
Andersson I, Backlund A. Structure and function of Rubisco. Plant Physiology and Biochemistry. 2008.
📋 Metadata
Process Statistics

Nodes: 15 | Edges: 15 | OR Gates: 1 | AND Gates: 0

OR gate: Output or Regenerate? (one in, two out). Sequential AND: CO2 and RuBP both required for carboxylation; ATP and NADPH for reduction.