Breath and a metabolism. Supply by energy and building blocks. Synthesis and disintegration lipidov

you are: Breath and a metabolism. Supply by energy and building blocks

Intermediate products of process of breath are a source of carbon skeletons for synthesis lipidov which act and as spare substances, and as components of the membranes surrounding cytoplasm and all cellular organelly. Molecules lipidov, such as fats and oils, consist of three fat acids (fig. 5.13), connected by radio communications with three-carbon spirit glycerine.

Fats differ from oils mainly that they at a room temperature happen firm, and oils - liquid. Distinction it is defined by length of carbon chains of fat acids and degree of their nonsaturation (number of double communications). At oils carbon chains of fat acids are shorter, than at fats, and nonsaturation degree above.

Lipidy are sometimes the main form of spare nutrients. Seeds of a soya, sunflower, rapsa, kunzhuta and a cotton are very rich lipidami, in particular. Above we already noticed that in lipidah contains less oxygen, than in sugars, and it means that energy is reserved in them in more concentrated form as more oxygen it is required to transform them in СО2 and H2О. At combustion of one gramme of sugar it is allocated four calories, and at combustion of gramme of fat - nine. Very important role play lipidy and in maintenance of structure of a cage because all cellular membranes consist mainly from fosfolipidov and the squirrel. Lipidy membranes differ from usual fats that at them in a molecule one of three fat acids is replaced on fosforilirovannyj series, holin or etanolamin (fig. 5.14). Molecules of such structure rastvorimy partially in fats and partially in water, therefore they can settle down on border has undressed oil - water, and to regulate receipt zhiro - or water-soluble substances. Other important group make lipidy, connected to carbohydrates, so-called glikolipidy; they provide perception of irritation at interaction between cages.

As spare substances lipidy are present at cytoplasm in the form of oil droplets. In itself lipidy on a plant are not transported, but their carbon skeletons can be transported after transformation lipidov in sucrose. Then in other part of a plant lipidy again are synthesised from the sucrose which has arrived here. Glycerine and fat acids are necessary for synthesis lipidov. These connections are formed, as it is known, of intermediate products of process of breath and consequently sucrose transformation in lipidy is made easily.

The Glycerin which is a part of a molecule of fat, is formed in shape a-glitserofosfata from dioksiatsetonfosfata, the three-carbon connection which are one of intermediate products glikoliza. The fat acids entering connection with glycerine, are formed from Acetyl-soa by an indirect way (fig. 5.15). At first Acetyl-soa with the assistance of ATR reacts with СО2. A product of this reaction is malonil-SoA in which to SoA it is attached not so two-carbon, and a three-carbon fragment. Malonil-SoA loses then СО2 and transfers remained two-carbon atsetilnuju group to other molecule Acetyl-soa so to SoA there is now attached already four-carbon fragment, i.e. It is formed butiril-SoA. Process repeats until the chain of synthesised fat acid will not reach full length. As at each such stage to a synthesised carbon chain the two-carbon fragment from malonil-SoA is added, in natural fat acids the even number of atoms of carbon contains always. From the sated fat acids in plants are most of all extended palmitinovaja [СН3 (СН2) 14СООН] and stearin [CH3 (CH2) 16COOH],

And from nonsaturated - oleinovaja [СН3 (СН2) 7СН=SN (СН2) 7СООН], linolevaja [SNz (СН2) 3 (СН2СН== СН2) 2 (СН2) 7СООН] and linolenovaja [СН3 (СН2СН== SN) z (СН2) 7СООН] at which in a chain consisting of 18 atoms of carbon, two and three double communications contain accordingly one.

During all described process of synthesis the Soa-prorecension Th of fat acids remain attached to the special fiber representing a multifermental complex which is called atsilperenosjashchim as fiber (APB). At synthesis fosfolipidov with glitserofosfatom two Soa-derivatives of fat acids react only; the third carbon atom glitserofosfata joins any azotsoderzhashchee connection (holin, etanolamin or the series, connected with gidrofilnoj phosphatic group.

At disintegration lipidov glycerine and fat acids again are formed. These fat acids are activated, incorporating to SoA, and then are gradually split on two-carbon fragments by the enzymes which are from lateral aspect of a membrane glioksisom - organell, surrounded with a single-layered membrane. In glioksilatnyj a cycle (fig. 5.16) these two-carbon fragments join in a kind Acetyl-soa. One of the products formed inside glioksisom, four-carbon connection - amber acid is. Leaving from glioksisom, it arrives in mitohondrii and is involved here in a cycle of Krebsa in which acid finally is formed of it shchavelevouksusnaja (oksaloatsetat). Later in cytoplasm oksaloatsetat turns in fosfoenolpiruvat and again joins in geksozofosfaty as a result of the process representing the reference glikoliza; as an energy source serves for this purpose glioksilatnyj a cycle. A glyceric part of a molecule of fat reokisljaetsja to glitseraldegidfosfata. Last also can turn in geksozofosfaty from which then sucrose or some other metabolity is synthesised.

Such various ways the carbon fixed in the course of photosynthesis, passes eventually in all organic components of a plant. Thanks to the specific enzymes the plant operates as the skilful chemist; in it such difficult structures which the person for the present has not learnt to create are synthesised even.