Calvin Cycle
The Calvin Cycle is a light-independent process of photosynthesis where carbon dioxide is converted into glucose using ATP and NADPH generated during the light-dependent reactions.
Calvin Cycle
The Calvin Cycle, also known as the Calvin-Benson-Bassham Cycle, represents the second major stage of photosynthesis, occurring in the chloroplast of plant cells. This crucial metabolic pathway demonstrates how organisms convert inorganic carbon into organic compounds essential for life.
Core Process
The cycle consists of three distinct phases:
-
Carbon Fixation
- CO₂ combines with ribulose bisphosphate
- Catalyzed by RuBisCO, forming 3-phosphoglycerate
- Requires energy from ATP
-
Reduction
- 3-phosphoglycerate is converted to G3P
- Uses NADPH as reducing power
- Consumes additional ATP
-
Regeneration
- RuBP is regenerated
- Maintains cycle continuity
- Complex series of enzyme reactions
Environmental Factors
The efficiency of the Calvin Cycle is influenced by several factors:
- temperature
- CO₂ concentration
- Water availability
- cellular respiration
Significance
The Calvin Cycle is fundamental to:
- primary production
- Global carbon fixation
- food chain sustainability
- agriculture productivity
Regulation
The cycle is tightly regulated through:
- circadian rhythm
- enzyme inhibition
- hormone
- Environmental signals
Evolution and Adaptation
Different plants have evolved variations of the Calvin Cycle, leading to specialized adaptations like C4 photosynthesis and CAM photosynthesis.
Scientific History
The pathway was discovered by Melvin Calvin and colleagues in the 1940s, earning them the Nobel Prize in 1961. Their work used radioactive carbon-14 to track the movement of carbon through the cycle.
Applications
Understanding the Calvin Cycle has important implications for:
The Calvin Cycle remains an active area of research as scientists seek to optimize its efficiency for addressing global challenges in agriculture and climate change mitigation.