Polypeptide chains form the protein’s characteristics

In biosynthesis, the protein forming generates water from the losing hydrogen and oxygen

Previous article explaining the protein suggested that the protein is classified into several types based on the R side of the structure. Nevertheless, every protein has the same monomer called –NH2. Thus, the structure then is bonded by another monomer. How did it perform?

Have look one protein, for instance the cysteine which has chemical structure [–CH2—SH]. This monomer then meets the exact monomer and their structures become [–CH2—SH] + [–CH2—SH]. During the biosynthesis of protein, the two cysteine exact sides are formed together and they are try to stable their reaction which was occurred because of the presence of oxidation process. As a result, the synthesis produced water and left the –CH2—S—S—CH2—. The sulfur HS compound is cracked and it forms the disulfide bond.

Thus, the protein biosynthesis is commenced between amino acids and they are reacted and one loses a hydrogen and oxygen. When happening, the losing hydrogen and oxygen respectively are from the carboxyl group and amino group resulting the presence of water at the end. The presence of water indicates that the amino acids are bonded together because the oxygen and hydrogen are released by the amino acids structure. This bonding is called peptide bond, and if the bonding consists two amino acids it will be called dipeptide; three amino acids bonded together is called tripeptide. While oligopeptide is defined as a chain of several amino acids, for instance 10. For n- chains, we define it as polypeptide.

In term of properties, proteins that has polypeptide chair have common certain structural properties. For instance, most of the polypeptide chains consists a free amino and carboxylic acid group. These two groups are formed the polypeptide leaving the –N and –C during the biosynthesis. Interestingly, this property is the method of determining the type of the protein because it becomes the chain formula to understand the protein itself.

Another property that must to be understood is the amino and carboxyl group too. The side groups provide ionization reaction occurring –NH3+ and –COO- creating charge condition. As the result, the polypeptide chains are in charging condition which can influence the pH. The charged polypeptide implies the pH condition and this is known as the isoelectric point of the protein.

On the other hand, the proteins contain different sequence which can be happened from modification. The monomers’ sequences comprise amino acid residues and this could influence the properties. The differences in amino acid residues create different molecular weight indicating there are residues which includes the more complex organic molecules or simple metal ions. These groups are known as prosthetic group implying the physical and chemical characteristics of the protein itself.

References
[1] E. A. MacGregor, "Biopolymers," in Encyclopedia of Physical Science and Technology, San Diego, Academic Press, 2002, pp. 207-245.
[2] Image is downloaded from http://www.chem.ucla.edu