Photosynthesis. Energy storage. Photosynthesis. General idea

you are: Photosynthesis. Energy storage

When radiation of the corresponding length of a wave is absorbed hloroplastom, carbon dioxide is chemically restored to sugars, and gaseous oxygen is allocated in volume; equal to volume restored СО2. These changes are opposite in a direction to the changes occurring at oxidation of nutrients in the course of breath; hence, the important role of plants in balance of the nature is connected and that they return oxygen which is necessary for breath for the overwhelming majority of organisms in atmosphere. Having designated the formula (СН20) elementary unit of a molecule of carbohydrates (the molecule of glucose C6H1206 is constructed of six such units), we can write down the general equation of photosynthesis in a following kind:

All components of this reaction contain oxygen so the resulted equation speaks nothing about that, oxygen allocated at photosynthesis whence undertakes: from СО2 or from Н20. For many years biologists believed that light energy is spent for splitting of molecule СО2 and carrying over of atom With on Н2О with formation (СН2О). However supervision over photosynthesizing microorganisms have shaken this representation. Biochemical ways at the photosynthesizing microorganisms, as a whole similar to corresponding processes at the higher plants, nevertheless differ from them a little. For example, photosynthesizing purple bacteria use at photosynthesis not Н2О, a H2S and as a photosynthesis by-product allocate not oxygen, and sulphur:

The adjournment of sulphur formed by such way serve In many places of globe as the important natural source of elementary sulphur. Abundantly clear that this sulphur can occur only from H2S, split in the course of photosynthesis. Some seaweed which it is possible ' to accustom ' to use instead of water gaseous hydrogen Н2 for restoration СО2 to (СН2О) similarly behave, i.e. To level of carbohydrates:

Clearly that in both these mechanisms light energy is spent for decomposition (fotoliz) the donor of hydrogen, and the regenerative force generated by such way, is used for transformation СО2 in (СН2О).

If different organisms have any general way of photosynthesis the cited data allows to assume, as at the higher plants light energy is spent for water decomposition. To be convinced that this assumption is true, it was possible, when biochemists began to apply to studying of photosynthesis Н2О or СО2, mechennye a heavy isotope of oxygen (18О). In these experiences it has been shown that allocated oxygen always corresponds on the isotope structure to the oxygen containing in water, instead of in СО2. In effect, fotoliz waters is a key to all process of photosynthesis as at this stage light energy is used for manufacture of chemical work.

In a molecule of the oxygen allocated at photosynthesis at the higher plants, two atoms of oxygen, and in a water molecule - only one such atom contain, and it means that two molecules of water should enter reaction.

To receive the balanced equation correctly reflecting the mechanism of total reaction, we should enter in both parts of this equation on one molecule of water. If water contains 18О we will receive

If we mark with the help 18О carbon dioxide the equation will assume the following air:

Oxygen Allocated at photosynthesis turns out from the water entering reaction, the formed molecule of water differs from those two molecules which have undergone fotolizu. On fig. 4.1 the scheme which can help to imagine more visually to the reader the general course of considered reaction is resulted. From this scheme it is visible that light energy is used for water decomposition. Oxygen is thus allocated and formed also ' hydrogen ' (or ' regenerative force '), spent 1) on restoration СО2 to a photosynthesis end-product (СН2О) and 2) on formation of a new molecule of water Certainly, this most short description of photosynthesis, and in each of the simple reactions presented here actually there are many intermediate stages. One of these stages are connected with transformation of light energy in chemical, others can occur as on light, and in the dark. These last are called ' temnovymi as reactions ' photosynthesis.