Photosynthesis

Photosynthesis is a biochemical process in which plant, algae, and some bacteria harness the energy of light to produce food. Nearly all living things depend on energy produced from photosynthesis for their nourishment, making it vital to life on Earth. It is also responsible for producing the oxygen that makes up a large portion of the Earths atmosphere. Factors that affect photosynthesis are light intensity and wave length, carbon dioxide concentration, and temperature.
Plants are autotrophs that mean they are able to synthesize food directly from inorganic compounds, instead of relying on other organisms. They use carbon dioxide gas and water to produce sugars and oxygen gas. The energy for these processes comes from photosynthesis. The equation for photosynthesis is:
Carbon dioxide+water+light,sugar+oxygen+water.

6CO +12H O+light,C H O+6O +6H O
The glucose is used to form other organic compounds, such as cellulose, or it may be used as fuel. This takes place through respiration found in both animals and plants. Respiration is the opposite of photosynthesis. Both respiration and photosynthesis take place through a complex sequence of steps, and are very different in detail.

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Plants capture light using the pigment chlorophyll, which gives them the green colour. This is contained in organelles called chloroplasts. Although all green plants have chloroplasts, most of the energy is produced in the leaves. The cells in the interior tissues of a leaf, called the mesophyll, contain about half a million chloroplasts for every square millimeter of the leaf. The surface of the leaf is uniformly coated with a water-resistant waxy cuticle that protects the leaf from excessive absorption of light and evaporation of water. The transparent, colourless epidermis layer allows light to pass through to the mesophyll cells where most of the photosynthesis takes place.


To metabolic pathways involved in photosynthesis are light reaction and dark reaction. The first stage of the photosynthetic system is the light-dependent reaction, which converts solar energy into chemical energy. Light absorbed by chlorophyll or other photosynthetic pigments is used to drive a transfer of electrons and hydrogen from water to and acceptor called NADP , reducing it to the form of NADPH by adding a pair of electrons and a single proton. The water or some other donor molecule is split in the process. The light reaction also generates ADP, a process called photophosphorylation. ATP is a versatile source of chemical energy used in most biological processes. The light reaction produces no carbohydrates such as sugars.


In photosynthesis, the dark reactions are chemical reactions that convert carbon dioxide and other compounds into glucose. These reactions unlike light-dependent reactions do not need light to occur. These reactions take the products of the light-dependent reactions and perform further chemical processes on them. The light-dependent reactions are carbon fixation and Calvin cycle.