What happens during photosynthesis?
The equation for photosynthesis shows only the reactants and the end products.
6CO2 + 6H2O =========> C6H12O6 + 6O2
carbon dioxide + water =========> glucose + oxygen
- the green chemical chlorophyll absorbs light
- the energy is used to rearrange the atoms of carbon dioxide and water
- the products are glucose (a sugar) and oxygen (a waste product)
How do plants use the glucose?
- convert some of the glucose into chemicals needed for growth of plant cells, such as cellulose, protein and chlorophyll
- convert some into starch for storage
- use some respiration to release energy
Because it is insoluble, starch has little effect on the osmotic balance of cells. A high concentration of glucose cause water to be drawn into cells. So, starch is a better storage molecule than glucose.
Energy released in respiration is used to synthesise polymers such as;
- starch and cellulose from glucose
- amino acids and then proteins from glucose and nitrates
Plants roots absorb nitrates by active transport, a process that requires energy.
Why does the rate of photosynthesis vary?
The rate of photosynthesis may be limited by low;
- carbon dioxide concentration
- light intensity
The amounts of carbon dioxide and oxygen exchanged over a 24-hour period vary. At compensation points, the rate pf photosynthesis and respiration balance, so there is no net movement of these gases between a plant and the surrounding atmosphere.
The rate of photosynthesis is limited by the factor that is in the shortest supply.