BRAINCAKECarbon Dioxide
Carbon dioxide is a substrate of the light-independent reactions (the Calvin cycle) in the stroma. The enzyme RuBisCO fixes carbon dioxide by combining it with the 5-carbon compound RuBP. The unstable 6-carbon product immediately splits into two molecules of the 3-carbon compound GP, which is then reduced to GALP using ATP and reduced NADP.
Carbon dioxide diffuses into the leaf through the stomata. The atmosphere contains only about 0.04% carbon dioxide, so on a bright, warm day carbon dioxide concentration is often the limiting factor. Increasing its concentration increases the rate of photosynthesis until another factor, such as light intensity or temperature, becomes limiting.
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Key terms in this lesson
- gp
- The three-carbon compound formed when RuBP combines with carbon dioxide in the Calvin cycle, before being reduced to GALP.
More in Photosynthesis
- The Calvin Cycle
- The Products of Photosynthesis
- C4 Plants
- Rubisco
- Limiting Factors of Photosynthesis
- Light
- Temperature
- Limiting Factors in the Wild
All 20 lessons in Photosynthesis · All Edexcel A-level Biology topics