Photosynthesis en ingles

Photosynthesis

18/Junio/2010

Photosynthesis is the process by which green plants make carbohydrates from carbon dioxide and water using sunlight energy absorbed by chlorophyll. Oxygen gas is aby-product of the process.

Aristotle was the first to study it. He wanted to know how plants are able to produce food for their own use. He put two observations together and formed the hypothesisthat plant roots extract decayed materials from soil, and that these materials are used by the rest of the plant for the production of food.

The mechanism of photosynthesis

There are four mainfactors involved in photosynthesis: water, carbon dioxide gas, the green pigment chlorophyll, and the energy of sunlight. These are the raw materials; the major products are carbohydrate and oxygen.During photosynthesis plants make sugars such as glucose. To do this, the energy of light is absorbed by chlorophyll and used to combine carbon dioxide and water. Oxygen is released as a by-product anddiffuses out of the plant into the atmosphere.

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Photosynthesis occurs in the chloroplasts where chlorophyll is located. Evidence indicates that photosynthesis is a two-stage process, thefirst requiring light and the second capable of occurring in the dark. The function of the light stage is to produce ATP, and to split water (the Hill reaction), thus providing hydrogen atoms for thesubsequent reduction of carbon dioxide. In the dark stage the carbon dioxide is reduced and carbohydrate synthesized via the Calvin cycle.

In the light stage electrons are removed from chlorophylland either passed back to chlorophyll via a series of carriers with the production of ATP, or combined with hydrogen ions to form hydrogen atoms for the dark reactions. The hydrogen atoms aretransferred to dark stage by NADP in the final step of a process which involves the transfer of electrons through two chlorophyll pigment systems.

In the dark stage carbon dioxide is fixed, reduced by the...