Photosynthesis is the chemical change which happens in the leaves of green plants. It is the first step towards making food, during this reaction; carbon dioxide and water are converted into glucose and oxygen. The reaction requires light energy, which is absorbed by a green substance called chlorophyll. Photosynthesis takes place in leaf cells. These contain chloroplasts, which are tiny objects containing chlorophyll.
carbon dioxide + water (+ light energy) → glucose + oxygen
6CO2 + 6H2O C6H12O6 + 6O2
Plant cell involved in production of glucose from photosynthesis
Chloroplasts - containing chlorophyll and enzymes needed for reactions in photosynthesis.
Nucleus - containing DNA carrying the genetic code for enzymes and other proteins used in photosynthesis
Cell membrane - allowing gas and water to pass in and out of the cell while controlling the passage of other molecules
Vacuole - containing cell sap to keep the cell turgid
Cell wall - strengthens the cell
Cytoplasm - enzymes and other proteins used in photosynthesis made here
Factors which may affect photosynthesis
Light intensity - if the light is brighter, then the rate of photosynthesis increases. Many plants spread out their leaves in such a way that each leaf maximises the amount of light falling on them and the lower leaves are not shaded by the ones above. Too much light at a high intensity can damage chloroplasts.
Temperature - The higher the temperature then the greater the rate of photosynthesis, photosynthesis is a chemical reaction and the rate of the chemical reaction increases with temperature. However, for at temperatures above 40°C the rate slows down. This is because all enzymes are proteins and at too high temperatures the proteins break down. The active site of the enzyme becomes distorted and so the substrate no longer fits and hence the reaction does not occur. You can say the enzymes have denatured.
Carbon dioxide - is used to make sugar in the photosynthesis reaction. An increase in the concentration of carbon dioxide gives an increase in the rate of photosynthesis. It is easier to do this in a greenhouse. Many crops such as tomatoes give higher yield when grown in greenhouses. People add additional carbon dioxide into the greenhouse to increase the concentration and so the rate of photosynthesis of the crops.
The factor I will be investigating is light intensity and how it affects the rate of photosynthesis, I have chosen this because I believe it is the easiest variable to change with the apparatus I have and will be able to get the best most reliable results. Also with light intensity I feel I will get the widest range of results and easily show how light affects the rate of photosynthesis.
Prediction: I predict that the closer the lamp is to the plant the more oxygen bubbles will be produced, hence the higher the rate of photosynthesis, for example when the lamp is 5cm away from the Cabomba plant, the number of oxygen bubbles produced will be the greatest and also double the amount of bubbles you get when the lamp is 10cm away, and the further away the plant is to the lamp, the lower the number of oxygen bubbles are produced, for example when the lamp is 25cm away…