Proteins are macromolecules that play an important role in the cell. The cell synthesizes proteins using amino acids. About 20 amino acids are found in human beings and are involve in protein synthesis.
The proteins are formed in 4 steps as follows:
1. Primary structure: Here the amino acids are linked together to form a peptide chain. The amino acids are linked to each other by peptide bonds.
2. Secondary structure: The peptide chain gets folded into secondary structure due to hydrogen bonds. These structures are of two types: α helix and β- pleated sheets. The name is given as per the conformation of secondary structure form.
3. Tertiary structure: The secondary structure gets further folded to form a compact structure called the tertiary structure in a process which involves hydrogen bonding and van der waals forces.
4. Quaternary structure: Tertiary structures that come together to form a macromolecule consisting of the same or different tertiary structures are termed as quaternary structures.
The outer layer of the cell is known as the cell membrane. The cell membrane carries out various important functions in the cell such as cell transport and cell signaling. Cell signaling and transport are mainly assisted by set of proteins termed as transmembrane proteins. The proteins span the cell membrane and opens up interior and exterior of the cell.
The amino acid sequence of transmembrane proteins can be used to predict how the protein will span the membrane, since the cell membrane is lipophilic in nature. The protein region spanning within the cell membrane would consist of a hydrophobic region whereas the other two ends had to be hydrophilic.
The terminal regions would consist of hydrophilic amino acids such as aspartic and glutamic acid and arginine whereas hydrophobic amino acid such as alanine, valine and leucine would constitute the transmembrane region.