Disassembling and Reassembling of Proteins - Essay Example

Disassembling of Proteins Proteins form part of the human diet, and are of significant importance repair processes in the body. Proteins usually perform multiple roles in the body, and exhibit a great level of diversity. Dietary proteins usually undergo dissembling into amino acids, which are the building blocks. The body only has the potential to absorb amino acids, explaining why the body embarks on the digestive process. After entry of proteins in the mouth, the change that takes place in the stomach involves the mechanical breakage of solid proteins. After leaving the stomach, food goes through the oesophagus into the stomach where the onset of protein digestion occurs. The hydrochloric acid is released in preparation for digestion, and plays a critical role in activating pepsinogen into pepsin, the enzyme that catalyses the breakdown of proteins. The HCl intrinsic factor also aids in the conversion of proteins into metaproteins, making the catalysis of the breakdown easier since peptidases break down metaproteins easily. Interaction of proteins with hydrochloric acid triggers denaturation, making digestion easier. The acidic environment serves as a favorable environment for the activity of the activated pepsin. Pepsin takes an active role in breaking down proteins into peptides. Digestion of protein continues in the small intestines because pepsin activity of breaking down proteins is partial. The resulting peptides need further digestion in their constitute amino acids that can be absorbed by the small intestines DNA (The Open University 2004, p. 143). In the case of infants, the enzyme rennin is present in the stomach, and its major responsibility is acting on casein, converting it to a soluble protein molecule named paracasein. In the reaction that follows, calcium ions encounter paracasein, and calcium paracaseinate forms. Pepsin then acts on paracaseinate, digestive it into simpler molecules. In the small intestines, pancreaticpeptidases such as trypsin, chymotrypsin, elastase, and carboxypeptidase indulge in further digestion of the peptides. Trypsin is a specific enteropeptidase that serves to hydrolyze the central peptide bond defined by carboxyl groups emanating from basic amino acids. This implies that trypsin specializes in hydrolyzing the bonds where arginine, lysine, and histidine are located. Similar to other enzymes, trypsin production must be in the inactive form, to ensure that it does not digest the inner lining of the small intestines. The enzyme has an auto-activation system through the release of the enterokinase enzyme. Chymotrypsin is additional enzyme that acts on the central peptide bonds formed by carboxyl groups that belong to aromatic amino acids. It is also produced in its inactive form chymotrypsinogen DNA (The Open University 2004, p. 146). Its activation results from the presence of trypsin. Elastase is the third pancreatic peptidase that exhibits its activity in the small intestines. Although its production occurs in the inactive form, the presence of activated trypsin serves to activate it, making it ready to digest elastin and collagen. Carboxypepetidase is the fourth pancreatic enzyme whose function in the small intestines cannot receive any form of underestimation, and serves to hydrolyze the terminal peptide bond that is present at the carboxyl terminus of the peptide chains. Its inactive form is procarboxypeptidase and undergoes activation in the presence of trypsin. In addition, intestinal juice contains additional peptides such as aminopeptidase, tripeptidase and dipeptidase that finish the digestion of peptides into free amino acids. The free amino acids released after the complete digestion of proteins are absorbed through a rapid process that relies on ATP in the duodenum and jejunum. This marks the end of the disassembling process of the protein in the diet DNA (The Open University 2004, p. 149). Reassembling Amino Acids to form Useful Proteins Protein synthesis is a process that occurs in conformity to genetic instruction. The genetic material occurs in the cell in the form of deoxyribonucleic acid (DNA) in the chromosomes. The body exhibits a diverse need for proteins as enzymes, hormones, transport proteins, contractile proteins, and antibodies. Proteins exhibit abundance that surpasses all other molecules in the body. This explains why the assembly of amino acids to make useful proteins is one of the most critical functions of cells. Any dysfunction incapacitating the cells from protein synthesis registers serious consequences. Gene expression is the integral process in protein synthesis. The initial process of gene expression is transcription, which involves the formation of a messenger RNA that is complementary to a single strand of the double stranded DNA (The Open University 2004, p.68). Transcription occurs under the catalytic potential of RNA polymerase. The polymerase enzyme requires the sigma factor that attaches to the core enzyme, and begins the transcription process at the initial sequences after the promoter sequence. Transcription yields the messenger RNA transcript, which is used in the translation process. After transcription, messenger RNAs move to the ribosome, where translation takes place. Translation occurs at the ribosomes, with the transcriptase enzyme producing anticodons that determine the amino acids to be assembled. The ribosomes attach themselves to the messenger RNA and begin to translate the sequence of the RNA into three base codons that determine the amino acid to be added. It is worth noting that different codons may represent a single amino acid. The transfer RNAs are very important because they carry the amino acids to the ribosome. The addition of these amino acids to the growing peptide chain serves to form the required protein. A high level of specificity is critical in both the translation and the transcription process because any mistake would result to dysfunctional proteins. After translation, the formed peptides find their way into the rumen of the endoplasmic reticulum. In the reticulum, protein organization and folding occurs. Protein folding is critical after synthesis so that proteins may adopt their advanced structure. In the ribosomes, the peptides assemble are in their primary structure while they need to undergo further organizations to form secondary, tertiary, and quaternary structures depending on the synthesized protein. Different forces make protein folding and organization a reality, ensuring that they bind the peptide chains together DNA (The Open University 2004, p. 70). The order of amino acids in each protein is critical because it determines its folding, and functionality. This is the reason why mutations altering a single base in the DNA present adverse effects to the individual, as that mutation may affect either transcription or translation, and eventually the functionality of the protein formed. Conclusion Evidently, proteins ingested into the body as food undergo a disassembling process carried out by different peptidases in the stomach and the small intestines. Complete digestion yields free amino acids that find their way into the blood stream through the ATP dependent absorption process. These amino acids are of critical importance in assembling other useful proteins in the body as dictated by gene expression. The transcription and translation process determine the number, and order of amino acids assembled for each protein. Bibliography The Open University, 2004, Cells and Nutrition. Latimer Trend and Company Ltd, Plymouth. Read More