Difference Between Polypeptides and Polyamides

The key difference between polypeptides and polyamides is that polypeptides are polymer materials containing a large number of repeating units of amino acids, whereas polyamides are polymer materials containing a large number of repeating units of amide groups.

Both polypeptides and polyamides are amine-containing polymer materials. Polypeptides are naturally occurring bio-polymers whereas polyamides are artificially synthesized synthetic polymers.

CONTENTS

1. Overview and Key Difference
2. What are Polypeptides 
3. What are Polyamides 
4. Side by Side Comparison – Polypeptides vs Polyamides in Tabular Form
5. Summary

What are Polypeptides

Polypeptides are chains of amino acids and are biological polymer materials. Peptides can be found in proteins; a protein contains one or more polypeptide chains. Polypeptides contain amino acids that are linked to each other via peptide bonds, which are a type of covalent chemical bonds. There are two terminals in a polypeptide chain: N-terminal and C-terminal. The N-terminal is the amino-terminal, which ends with a free amino group, while the C-terminal is the carboxyl-terminal, which ends with a free carboxyl group. We can determine the sequence of amino acids present in a peptide via the observation of codons in the mRNA that occurs in the production of the polypeptide or the protein via translating the template strand.

There are four types of proteins structures, depending on the number and arrangement of polypeptides in a protein.

1. Primary structure – The primary structure of a protein contains a single polypeptide chain that has disulfide bridges between some amino acids in the same chain, which makes a folded structure.
2. Secondary structure – The secondary structure of a protein has two major forms: alpha-helix structure and beta-sheet structure.
3. Tertiary structure – This is a highly-folded network structure. This structure is very important since it determines the function of a protein.
4. Quaternary structure – This is a highly complex structure of two or three polypeptide chains that are linked to each other.

What are Polyamides?

Polyamides are polymer materials having a large number of repeating units of amide groups. These are high-performance thermoplastic elastomers characterized by their high service temperature, good heat ageing, and solvent resistance. Moreover, these polymers have high modulus and impact properties, low coefficient of friction, and high abrasion resistance. Nylon is the most common and widely used type of polyamide. Nowadays, nylon polymer is among one of the most important and widely consumed polymers in the United States.

Polyamides contain amide groups, which are polar groups. These polar groups allow polyamides to build hydrogen bonds between chains, thereby, improving the interchain attraction. This property of the polymer material enhances the mechanical properties of polyamide. For example, nylon contains flexible aliphatic carbon groups in the chain that improve the processability of the material by reducing the melt viscosity. The strength and stiffness of this material reduced when increasing the number of carbon atoms between the amide linkages. Therefore, the length of the hydrocarbon backbone is a key property that determines the performance of polyamide material. Due to the polarity of the amide group, polar solvents, mainly water, can affect polyamides.

There are two types of polyamides: aliphatic and aromatic polyamides. Nylon can be either an aliphatic or semi-aromatic polyamide. The main applications of polyamides include radiator header tanks in cooling systems, switches, connectors, ignition components, sensors and motor parts in auto electrical systems, wheel trims, throttle valves, engine covers, heat resistant under-bonnet components, airbrake tubing, etc.

What is the Difference Between Polypeptides and Polyamides?

Both polypeptides and polyamides are amine-containing polymer materials. Polypeptides are naturally occurring bio-polymers whereas polyamides are artificially synthesized synthetic polymers. The key difference between polypeptides and polyamides is that polypeptides are polymer materials containing a large number of repeating units of amino acids, whereas polyamides are polymer materials containing a large number of repeating units of amide groups.

The following table summarizes the difference between polypeptides and polyamides.

Summary – Polypeptides vs Polyamides

Polypeptides are naturally occurring bio-polymers whereas polyamides are artificially synthesized synthetic polymers. The key difference between polypeptides and polyamides is that polypeptides are polymer materials containing a large number of repeating units of amino acids, whereas polyamides are polymer materials containing a large number of repeating units of amide groups.

Reference:

1. “19.1: Polypeptides and Proteins.” Biology LibreTexts, Libretexts, 25 Sept. 2019, Available here.
2. “Polypeptides.” ScienceDirect Topics, Available here.

Image Courtesy:

1. “Glycosylation of a polypeptide” By Kep17 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Botte de fibres polyamides (rilsan)” By MRousse – Own work (CC BY-SA 4.0) via Commons Wikimedia