The peptide bond , strong, is responsible. It has adjacent atoms in the same plane where the fact that it is coplanar and Linear molecule. It has a partial double bond character of resonance between two forms. This confers it an almost full strength. The rotations are absent and there are two possible conformations for binding:. Cis or trans This is the trans conformation which is observed as energetically favored. Rotational movements are possible between the α carbon and N and between the α carbon and C.
polypeptides are unbranched polymers, so their primary structure can often be specified by the sequence of amino acids along their backbone. However, proteins can become cross-linked, most commonly by disulfide bonds, and the primary structure also requires specifying the cross-linking atoms, e.g., specifying the cysteines involved in the protein’s disulfide bonds. Other crosslinks include desmosine.
- Proteins are polypeptides made from 20 different monomers.
- On average contain 100-400 monomers.
- Each monomer has an approximate molecular mass of 110.
It is therefore easy to understand that the axial skeleton is non-specific protein but it is a common structure. Which gives its identity to a protein is the set of side chains of the proteinogenic amino acids the component. This set is the signature of the protein.
The Primary Structure:
Monomers –> Polymers
- Amino Acids form peptide bonds (from the carboxylic acid group on one to the amine group on another). This releases water in a condensation reaction. The location of the peptide bond (C-N) is shown below outlined in RED.
- When reading a sequence of Amino Acids in a protein, start at the Amino terminus (NH2 end) and read to the Carboxyl terminus at the other (COOH).
- The sequence of amino acids is known as the primary structure of a protein.
The amino acids in chains and proteins can be post-translationally modified – Eg, disulphide bridges can form between cysteine residues.