effect of carbon dioxide on rate of photosynthesis

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Planning of photosynthesis investigation


The aim of this experiment is to investigate into the effects of the change of carbon dioxide concentrations on the rate of photosynthesis.


My hypothesis is that as the concentration of carbon dioxide increases the rate of photosynthesis will also increase.

Graph showing the effects of carbon dioxide on the rate of photosynthesis

                Light intensity

Scientific reasoning:

Photosynthesis is the process by which chlorophyll containing organisms capture energy in the form of light and convert it to chemical energy.

Plants make food through a process called photosynthesis. Using energy from the sun, cells in the leaves turn simple materials into energy rich food. Spongy cells are partly surrounded with pockets of air, which enable the cells to exchange gases with the atmosphere. The stomata are small openings in the lower epidermis under the leaf. Carbon dioxide enters through the stomata. Carbon dioxide combines with water and is photosynthesised into oxygen and sugar.

Equation for photosynthesis

6 CO2 + 12H2OC6H12O6+ 6O2 + 6H2O

Oxygen escapes through the stomata and the sugar dissolved in water is carried throughout the plant providing energy for growth.

Photosynthesis consists of two stages: a series of light- dependent reactions, which are temperature independent and a series of light independent reactions, which are temperature dependent. Increasing light intensity can increase the rate of the light dependent reactions. Increasing the temperature can increase the rate of the light independent reactions.

Photosynthesis begins with the absorption of light by pigments. Chlorophyll and other pigments known as carotenoids absorb different wavelengths of light, which broadens the spectrum of light energy that can be fixed through photosynthesis. Photosynthesis takes place within cells called chloroplasts that contain the chlorophylls and enzymes that are necessary for various reactions.

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Carbon dioxide is important in the light independent reaction. This reaction takes place in the stroma (matrix) of the chloroplast, where the energy stored in the ATP and NADPH is used to reduce carbon dioxide to organic carbon. The is done by going through the reactions known as the Calvin cycle where one molecule of carbon dioxide enters and combines with a five-carbon sugar called RuBP (ribulose 1,5-biphosphate) to form two molecules of a three-carbon compound called GP (3-phosphoglycerate).

The factors that affect photosynthesis are wavelengths of light, temperature and carbon dioxide concentrations. Wavelengths of light effects ...

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