Biochemistry

Many substances (vitamins, hormones, metabolic products, etc.) can penetrate from the cytoplasm into the nucleus and cause disturbances despite the fact that the nucleus is surrounded by a shell. Such changes cause by metabolic disorders, which essentially include all hereditary diseases. For example, some people organism lack certain enzymes, which is why certain food substances are not broken down or absorbed in their bodies, for instance, whole fresh milk in the absence of lactase , an enzyme that breaks down lactose (milk sugar) in the intestines . At the heart of diseases such as phenylketonuria, histidinuria is a genetically determined weakening of the biosynthesis of enzymes that catalyze the oxidation of aminoacids - phenylalanine and histidine. In this regard, the concentration of these amino acids in the blood increases and their excretion in the urine increases. The phenylketonuria can cause a lag of mental development of the child. One of the effective methods of treating genetically determined disorders of amino acid metabolism, which is based on a violation of the synthesis of an enzyme (fermentopathy), is a diet that excludes food sources of amino acids or their derivatives that do not have the corresponding enzymes in the body. The genetic apparatus is very sensitive to y-rays, substances that pollute the biosphere, products of fat oxidation and other factors that can lead to its mutation. As a result of this, errors may occur when reading the code, and then foreign proteins will be synthesized not identical. A major role in disrupting the gene apparatus is played by viruses that cause various diseases: influenza, hepatitis, etc. Viruses having their own DNA can impose their code and "dictate ” M-RNA the wrong order of alternating nitrogenous bases in DNA. As a result, the synthesis of a foreign protein is possible. 9.3 REGULATION OF PROTEIN BIOSYNTHESIS A large number of proteins are synthesized in the cells of living organisms. This process is regulated by a precisely programmed mechanism, so that exactly the amount of protein is formed in each cell, which allows it to carry out metabolic processes with maximum efficiency. Regulatory mechanisms ensure the economical use of amino acids for the synthesis of proteins, including enzymes. Due to this, in any cell there is an appropriate set of enzymes that contributes to the nonnal course of basic cellular processes. Regulation of protein biosynthesis can be carried out at different levels. Based on the matrix hypothesis of protein biosynthesis, employees of the Pasteur Institute (in Paris) F. Jacob and J. Mono (1961) first proposed a scheme for 186