Investigating Photosynthesis

Investigating Photosynthesis
In its essence, photosynthesis is the process by which plants make their chemical energy. Most people think that the equation for photosynthesis is the complete process, though there are several steps until the atp can be made. To produce atp, light energy must first be captured. Within the leaf, there are two sets of pigments that are responsible for this. The first set is Chlorophyll; Ø Chlorophyll A which absorbs the yellow-green part of the spectrum Ø Chlorophyll B which absorbs the blue-green part of the spectrum The second set is Carotenoids; Ø β Carotene which absorbs the orange in the spectrum. Ø Xanthophyll which absorbs yellow from the spectrum. The reason for these pigments is that each pigment can absorb a certain wavelength or group of wavelengths. Without these pigments, these wavelengths would pass through the leaf and their chemical energy would be lost instead of harnessed. Chlorophylls generally absorb the red and blue-violet regions of the spectra hence the fact that they look green as they reflect green light. The carotenoids in mainly absorb the blue-violet wavelengths which is why they tend to look red/orangey.
Chloroplasts are the organelle responsible for trapping the light. Within the chloroplasts are a structure called Grana which consist of several Thylakoids. It is inside this thylakoid membrane that the process begins, there is a Â?funnelÂ? in which at the bottom there is primary pigment (Reaction Centre), along the side are many primary pigments, these absorb the various different wavelengths in the light and pass down the chemical energy down to the reaction centreÂ?this ensures that no energy is lost during the process, it also makes the process more efficient, as it ensures that no light energy passes through without being harnessed. There are two types of reactions, Light Dependant and Light Independent. Light dependant is the more common reaction as the light independent reaction only occurs when the light is made unavailable, the light independent reaction is also known as the Calvin Cycle. There are two photosystems involved in photosynthesis; Photosystem II is responsible for the generation of a proton gradient used to synthesize atp. It is also responsible for oxygen evolution as electrons are removed from water to replace those transferred to photosystem I. Photosystem I is responsible for the production of nadph, although it can also operate in a mode which produces a proton gradient, and thus atp. The nadph made in Photosystem II is then used in the light independent reaction, if need be. Photosynthesis is an essential chemical process that must take place in order for organisms such as us to survive. The process of photosynthesis releases oxygen and absorbs CO2 from the atmosphere which maintains a balance within the atmosphere. This balance however is being disrupted by the cutting down of trees, leading to excess pollution in the air. The excess of these gasses is thought to be the cause of the Greenhouse effect. The greenhouse effect has become more and more apparent as our society has become increasingly industrially based; this is due to factors such as deforestation. Plants are also a primary source of energy, as animals cannot photosynthesise and so consumed plants (phototrophs) for the energy that they produced.

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