Photosynthesis occurs in the chloroplasts of plant cells. It occurs in two main stages:
light-dependent reactions
light-independent reactions (Calvin cycle)
What is the role of chlorophyll in photosynthesis?
Chlorophyll absorbs lightenergy (mostly red and blue wavelengths) and converts it into chemical energy during the light-dependent reactions.
Oxidation is loss of protons/hydrogen
Reduction is gain of protons/hydrogen
The factors that affect the rate of photosynthesis include lightintensity, temperature and carbondioxide concentration.
Effect of Light Intensity on Photosynthesis:
As light intensity increases, the rate of photosynthesis generally increases. This is because more light energy is available to drive the light-dependent reactions, leading to greater production of ATP and NADPH.
At a certain point, further increases in light intensity do not lead to an increase in the rate of photosynthesis. This is known as the light saturation point. Beyond this point, other factors (like CO₂ concentration or temperature) become limiting.
Effect of Carbon Dioxide Concentration on Photosynthesis:
As the concentration of carbon dioxide increases, the rate of photosynthesis also increases. CO₂ is a key substrate for the Calvin cycle, where it is fixed into organic molecules.
When CO₂ levels are low, the rate of photosynthesis is limited because Rubisco cannot fix CO₂ to RuBP
Beyond a certain level, increasing CO₂ concentration will not further increase the rate of photosynthesis, as other factors (like lightintensity or temperature) may become limiting.
Effect of Temperature on Photosynthesis:
As temperature rises, enzyme activity generally increases, leading to a higher rate of photosynthesis up to an optimal temperature range.
This is due to the increased kineticenergy of molecules, resulting in more frequentenzyme-substrate collisions.
If the temperature exceeds the optimal range, enzyme activity begins to decrease due to denaturation. Enzymes lose their shape, leading to a decrease in the rate of photosynthesis.
