Eukaryotic transcription

While the bacteria RNA transcription directly synthesized DNA of eukaryotes most transcripts are processed in the nucleus that is modified before they are transported to the cytoplasm as differential mRNA, which would serve as carriers of information for protein synthesis. Unlike bacteria which Transcription and translation take place virtually at the same time, the eukaryotic these processes in terms of time but also the spatial are divided. The envelope of the nucleus possesses the subsequent role of the ribosome link to transcripts, before this becomes elaborated and functional molecule RNA.

In the nuclei of eukaryotic cells there are three types of RNA polymerase, RNA polymerase I, RNA polymerase II and III ARNpolimeraza.

Each of these enzymes consist of large number of subnjësive: two large and 12 small. As bacterial enzymes, and eukaryotic RNA polymerases are molecules with an irregular shape, the channel through which passes DNA. Bacterial RNA polymerase, however, unlike eukaryotic enzymes, is very active in vitro system. For its activity is essential presence of DNA, whereas eukaryotic enzyme activity depends on the presence of a range of additional factors.

This was the reason, for which up to 1979 it was not possible to investigate in vitro mechanism of eukaryotic transcription. Besides nuclear RNA polymerase, eukaryotic cells contain RNA polymerase in organelles, such as mitochondria and chloroplasts. Enzymes distinct from nuclear organelles.

Each of the three nuclear RNA polymerases and eukaryotic cells _transkripton different sets of genes. RNA polymerase II transcribed structural genes are translated into proteins. Two other polymerases synthesize RNA that are translatues cellular apparatus: RNA polymerase I synthesizes large ribosomal subunit RNA (18s and 28S).

Enzymes

Enzymes are biological catalysts, which are synthesized by living things. By enzymes in the cell biochemical reactions developed very fast in a very low temperature such as body temperature. Enzymes can only accelerate biochemical reactions, which although slowly can be performed even in their absence. They are able to act as a catalyst not only in cells that are formed, but also abroad. Reactions in which the participating enzymes, form the basis of all life phenomena.

Steroids

Steroids are composed of fatty acids linked to alcohol-sterol-monohidroksil citric. Are its constituent material for the cell, also entered its structural building, but if we encounter at large, are as protective material in action: the poison, or as active material or as biocatalysts.

The most common steroid in animal cells is cholesterol, which participates in the construction of the cell membrane.

Steroids are aromatic hydrocarbons consisting of three fused rings of six carbon atoms (heksonbenzeni), two of these rings lie in an adjacent level and above.

Various steroids are characterized by their ring structures. These are chains of carbon and various functional groups, ranging from C 21 steroid cortisol, C 19 steroid testosterone, estradiol, etc. C13 steroid.

Steroids are the main ingredients of sexual honnoneve (as above), cholesterol, vitamin D, bile acids and corticosteroids.

Sterol Kolestoroli is distributed throughout the cell and animal tissue in vcrdhën of dew., Various oils, fat, meat, cheese. Cholesterol is widespread in the body, most tcpënni in nerve tissue, as in the brain., Spinal cord and nerves.

Eukaryotic cells

The name was taken from the Greek word; eu - true and karyo nucleus. From its eukaryotic word, means that these cells are well differentiated nucleus. From an evolutionary perspective as a group are younger than prokaryotic cells and cellular composite arrangement.

Genomes of eukaryotic cells consists of one or more long chains of DNA (DNA polynucleotide), which are in association with the structural proteins called histone. Before eukaryotic cell division, distribution of genetic material carried by the route of a complex mechanism that is called mitosis.

Atomic radius

Alignment of the size and range of free atom is very complex. For their njehsimm atoms of 1 as spheres and that the atoms or ions crystalline substances affect one another. So, as we think atomic radius distance between the nucleus of an atom and its Valente layer. However, following the model of the atom quantum mechanics, there is a precise distance electron can be found away from the nucleus. Therefore, the atomic beam requires a special form.

There are two ways how the atomic beam is normally determined. The first is the radius of the metal, which is half the distance between two adjacent cores of the same atom. The other method is the covalent radius, which is half the distance between the two cores of the same atoms bonded to the molecule.

Periodic properties of elements

As seen, the electronic configuration of elements show a periodic dependence with increasing atomic number. Here we will examine how electronic configuration explains the periodic changing physical and chemical properties of elements. Originally will start with the notion of effective load nucleus.

Charge of the nucleus (Z) is simply the number of protons in the nucleus of an atom. Effective Charge of the nucleus (Zef) is the actual size of the positive load "experienced" by an electron in the atom. Because hydrogen has only one electron, is the only atom which loads the kernel and its effective loads are the same. In all other atoms, elcktmnet simultaneously withdrawn from the nucleus and pushed each other. This phenomenon is known as shade (defense). In atom with more electrons an electron is shaded (protected) from positive ngurkcsa börthames the other electrons in the atom.

Number of chromosomes

The number of chromosomes varies, but is constant and its specific type. In all chromosomes somatic cells found in pairs. Thus a person owns 23 pairs of chromosomes means a total of 46 chromosomes. Chromosomes of a pair of homologous chromosomes mark as originating in one of the other father of the mother. However, the masculine and feminine it, chromosomes of a couple distinguish between them by symbols. They male marked with signs x, y while those feminine marked with signs x, x. Chromosomes of this couple to couple respectively 23, call the sex chromosomes, while the other 22 chromosomes autozomale couples.