the Kernel, ribosomes and fiber synthesis. Enzymes

you are: the Kernel, ribosomes and fiber synthesis

Many of the fibers synthesised on ribosomes, regulate speed of certain cellular reactions. Such fibers possessing specific kataliticheskoj activity, are called as enzymes. Enzymes play to a cage a key role; all nature of a cage as they regulate chemical reactions in which those or other cellular components are synthesised depends on them finally. at some plants, for example, nasledstvenno the fixed distinction between versions with red and white tsvetkami is caused by distinction in the one and only pair of genes. In cages of petals the version with red tsvetkami has an enzyme, capable to transform colourless substance-predecessor in a red pigment; at a version with white tsvetkami such enzyme is not present. Nuclear DNA defines colour of petals by regulation of synthesis of this cytoplasmatic enzyme, katalizirujushchego formation of the painted substance from colourless (fig. 2.13). In cytoplasm this nuclear control is transferred at means matrix RNK, synthesised in a kernel, but showing the activity in cytoplasm, on ribosomes.

In any cage thousand enzymes contain, and each of them regulates any chemical reaction or group of the interconnected reactions. Many enzymes have been allocated from a cage, subjected clearing, and then zakristallizovany. It has appeared that all enzymes represent fibers or consist mainly of fiber. Some enzymes contain small prostetineskuju group of not albuminous nature. At others the molecule is capable to dissociate on two parts - big albuminous (apoferment) and smaller not albuminous (koferment) (fig. 2.14). In such cases neither apoferment, nor koferment separately do not possess kataliticheskoj activity; at dissotsiatsii kataliticheskaja activity disappears, but it can be restored completely if koferment and apoferment will incorporate again. Small amounts of certain metals and vitamins play the important role in various physiological processes as these metals or vitamins are kofermentami those or other specific enzymes; in their absence enzyme is not capable to function

And the cage biochemistry gets abnormal or even pathological character. Into structure of some enzymes enter, besides fiber, carbohydrates, lipidy or any other components. In such cases speak about glikoproteidah, lipoproteidah, etc.

Function kofermentov such metals, as iron carry out, manganese, zinc, molybdenum and magnesium, and such vitamins, as tiamin, riboflavin, nicotinic acid and piridoksin. Both in that, and in other group active koferment is sometimes not simply metal or vitamin, and more difficult structure. Iron, for example, can be a part gema; it occupies the central position in this difficult organic molecule containing in haemoglobin and some important oxidising enzymes. Tiamin, riboflavin and nicotinic acid meet in a kind fosforilirovannyh the derivatives providing activity of some respiratory enzymes. Among so-called metallflavoproteidov there are enzymes which require several types kofermentov; so, aldegidoksidaza in the active form contains (besides the basic structural fiber) also free iron, iron in structure gema and, at last, riboflavin in a complex carrying the name flavin-adenindinukleotid. All these kofermenty are necessary for activity display aldegidoksidazy, and, for this purpose chtooy to be effective, each of them should be attached to fiber in corresponding position.

Enzymes katalizirujut the diversified chemical reactions - synthesis, disintegration, hydrolysis, oxidation, restoration and carrying over of groups (such, as amino groups, metilnye groups or the rests of phosphoric acid). Usually one enzyme kataliziruet only one any reaction or one type of reactions. Apparently, all enzymes carry out the function by the same way - at first they form a chemical complex with those substances on which operate (i.e. With the substrata).

This enzyme-substratnyj undergoes a complex then some internal reorganisations causing changes in a molecule of a substratum and finally leading liberation of products of reaction (fig. 2.15. We Will imagine that two small molecules And and In are capable to enter slowly connection with formation of larger molecule AV and that enzyme E accelerates (kataliziruet) this reaction. Total reaction

Consists, as it is possible to show, from following stages:

Summarizing these equations, we also will receive reaction А+В-> AV in which enzyme as the participant of reaction does not appear. Enzyme in total reaction acts as the catalyst thanks to that at last stage there is its regeneration; an enzyme small amount it appears to cause enough rather considerable general changes at substratum and product level (fig. 2.15 see,). In many cases speed kataliziruemoj reaction enzyme changes with increase in concentration of a substratum [SJ how is shown on fig. 2.16. At constant concentration of enzyme dependence between v and [S] appears almost linear until [S] is small, i.e. While addition of each new unit S increases quantity ES; however v does not depend almost from [S] at high values [S], i.e. When all enzyme is in form ES. Having constructed the schedule of double return sizes, i.e. The dependence schedule 1/v from 1 / [S], we will receive a straight line (fig. 2.17). Advantage of this way of the image consists that he allows to analyze biochemical reaction at infringement of function of enzyme. It is known, for example, that at action of some ingibitorov, competing to a substratum for linkage with the active centre of enzyme, the straight line inclination changes, but the size of the piece cut by this straight line on an axis of ordinates does not change. The similar analysis is useful when it is required to find any way which would allow to deduce enzyme from the blocked condition.

So, the cellular enzymes localised in various cellular organellah or in cytoplasm, directly operate activity of all biochemical device of a cage.

All cages are that, what they are, thanks to the himizmu; himizm cages it is defined by enzymes; the nature of enzymes is defined cytoplasmatic RNK; specificity of this RNK is in turn defined DNA, containing in a kernel and in some other cellular organellah.