Photosynthesis is the conversion of light energy into chemical energy in plants. It is a metabolic pathway that uses carbon dioxide and water to produce complex carbohydrates.
Visible light has a range of wavelengths, the shortest wavelength is violet, the longest one is red. Light ranges from 400nm to 700nm. Visible light is used by plants because it is emitted in large quantities by the sun, and it penetrates the atmosphere more than other wavelengths, they are primarily abundant. Pigments are substances that reflect light and therefore appear coloured. The pigment that absorbs all visible light, appears black, as they do not reflect any wavelength of visible light. Photosynthesis uses three pigments, chlorophyll a, chlorophyll b and carotenoid. Chlorophyll a is the primary pigment, while chlorophyll b and carotenoids are used as accessory pigments to chlorophyll a to increase the spectrum that drives photosynthesis.
The action spectrum of photosynthesis and absorption spectrum of chlorophyll overlap each other, this shows us that chlorophyll a is the most important of the photosynthetic pigments, because there is more of it in each plant.
Light dependent reactions use light energy to produce ATP (Adenosine triphosphate) and to split water. Splitting of water molecules is called photolysis and is one of the uses of energy consumed.
There are many factors that affect the rate of photosynthesis; major factors include, light intensity, carbon dioxide concentration and temperature. When light intensity (the amount of light, or a given wavelength, available to the organism – swap around) increases, the rate of photosynthesis increases, it is a limiting factor only at a low level. Carbon dioxide is a substrate for metabolic pathways, and so, its relationship with photosynthesis is similar to how enzyme reactions are limited by substrate concentration. So, when carbon dioxide concentration is increased, the rate of photosynthesis also increases. Therefore, it is a limiting factor in low concentrations. When temperature affects plants, it is also very similar to the way enzyme reactions are affected by temperature. As there are increases in temperature, molecules gain more kinetic energy which increases the rate of photosynthesis. There is an optimum temperature that causes the rate of photosynthesis to continue to increase consistently and eventually it peaks. After this peak, the enzymes are rapidly denaturing which causes a fast decrease in the rate of photosynthesis, as the temperature continues to increase.
Oxygenic (non-cyclic) photosynthesis provides energy for the organism and incorporates carbon into the organic compounds by living organisms, as well as producing oxygen as a by-product. This process releases oxygen, and while there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is very similar for all the organisms who carry it out. For this type of photosynthesis, the electron donor is water, and therefore since oxygen is released during hydrolysis releases oxygen, the equation is a following

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