Reacciones metabolicas catabolicas y anabolicas

Even though the ribosomes are usually considered accurate and processive machines, the translation process is subject to errors that can lead either to the synthesis of erroneous proteins or to the premature abandonment of translation. The rate of error in synthesizing proteins has been estimated to be between 1/10 5 and 1/10 3 misincorporated amino acids, depending on the experimental conditions. [7] The rate of premature translation abandonment, instead, has been estimated to be of the order of magnitude of 10 −4 events per translated codon. [8] The correct amino acid is covalently bonded to the correct transfer RNA (tRNA) by amino acyl transferases. The amino acid is joined by its carboxyl group to the 3' OH of the tRNA by an ester bond . When the tRNA has an amino acid linked to it, the tRNA is termed "charged". Initiation involves the small subunit of the ribosome binding to the 5' end of mRNA with the help of initiation factors (IF). Termination of the polypeptide happens when the A site of the ribosome faces a stop codon (UAA, UAG, or UGA) on the mRNA. tRNA usually cannot recognize or bind to stop codons. Instead, the stop codon induces the binding of a release factor protein that prompts the disassembly of the entire ribosome/mRNA complex and the hydrolysis and the release of the polypeptide chain from the ribosome. Drugs or special sequence motifs on the mRNA can change the ribosomal structure so that near-cognate tRNAs are bound to the stop codon instead of the release factors. In such cases of 'translational readthrough', translation continues until the ribosome encounters the next stop codon. [9]

Reactions can be exothermic , where ΔH is negative and energy is released. Typical examples of exothermic reactions are precipitation and crystallization , in which ordered solids are formed from disordered gaseous or liquid phases. In contrast, in endothermic reactions, heat is consumed from the environment. This can occur by increasing the entropy of the system, often through the formation of gaseous reaction products, which have high entropy. Since the entropy increases with temperature, many endothermic reactions preferably take place at high temperatures. On the contrary, many exothermic reactions such as crystallization occur at low temperatures. Changes in temperature can sometimes reverse the sign of the enthalpy of a reaction, as for the carbon monoxide reduction of molybdenum dioxide :

Reacciones metabolicas catabolicas y anabolicas

reacciones metabolicas catabolicas y anabolicas


reacciones metabolicas catabolicas y anabolicasreacciones metabolicas catabolicas y anabolicasreacciones metabolicas catabolicas y anabolicasreacciones metabolicas catabolicas y anabolicasreacciones metabolicas catabolicas y anabolicas