BRAINCAKELight Intensity as a Limiting Factor
Light provides the energy for the light-dependent stage. Photons are absorbed by chlorophyll in the photosystems of the thylakoid membranes, exciting electrons and driving photolysis of water, the electron transport chain and photophosphorylation. The products are ATP and reduced NADP, which are needed in the Calvin cycle.
At low light intensity, little ATP and reduced NADP are made, so the rate of photosynthesis is low. As light intensity increases, the rate increases in proportion, because light is the limiting factor. At high light intensity the rate levels off, because another factor such as carbon dioxide concentration or temperature is now limiting. Very high light intensity can damage chlorophyll.
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Key terms in this lesson
- rubp
- A 5-carbon compound in the Calvin cycle that combines with carbon dioxide, catalysed by RuBisCO, to form two molecules of GP.
- gp
- A 3-carbon compound formed when RuBP combines with carbon dioxide in the Calvin cycle, later reduced to triose phosphate.
- tp
- The 3-carbon sugar phosphate formed by reduction of GP in the Calvin cycle, used to regenerate RuBP and to make organic molecules.
More in Energy for Biological Processes
- Non-cyclic Photophosphorylation
- Chemiosmosis
- Calvin Cycle
- Limiting Factors of Photosynthesis
- Carbon Dioxide Concentration as a Limiting Factor
- Temperature as a Limiting Factor
- Interpreting Limiting Factor Graphs
- Effect of Limiting Factors on the Calvin Cycle
All 17 lessons in Energy for Biological Processes · All OCR A-level Biology topics