Wikibooks: GCSE Science/Photosynthesis

= Photosynthesis = Like all living things plants need food to live. This food is used for energy and to make new materials when plants grow. Plants are able to take two inorganic chemicals carbon dioxide gas and water to make an organic chemical glucose. This simple food can be used as an energy source or converted into other useful organic molecules. Photosynthesis takes place in chloroplasts the proteins that participated in the reaction are located in the thylakoid membranes of the chloroplast. Photosynthesis requires an input of energy. Plants have found a way to capture the energy from sunlight using a pigment called chlorophyll. Once this light energy has been captured it can be used to create glucose so converting the light energy into chemical energy. Oxygen gas is released as a waste chemical. The formula for photosynthesis is 6CO 2 + 6H 2 O rarr C 6 H 12 O 6 + 6O 2 carbon dioxide + water rarr glucose + oxygen The reaction reduces production of NADPH generates a proton gradient for the formation of ATP produces oxygen = Photosystems = There are two kinds of photosystems in photosynthesis that are called Photosystem I (PsI) and Photosystem II (PsII). During PsI a light absorbing pigment called chlorophyll which is a molecule that absorbs red light of 700 nanometer wavelength most efficiently we normally called it P700. On the other hand the pigment in PsII reaction center chlorophyll absorbs called P680 because it absorbs light at around 680 nanometers. The reason photosynthesis has two system is that one alone can t capture enough energy to power the carbon fixation reactions and to supply the rest of the energy requirements of plant metabolism. The combinations of these systems can cause different mechanisms to change the light energy to chemical energy therefore provide the maximum energy that plants require. The process however starts with PsII not PsI. The energy absorbed by a P680 molecule of chlorophyll in the reaction center of PsII first converts the molecule to its excited state and then raises ...