Peptides, Types & Classes, Molecular Biology, Applications, Peptide Bond, Characteristics (For CBSE, ICSE, IAS, NET, NRA 2022)

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Characteristics of Peptide Bonds

  • Peptide bonds are strong with partial double bond character:
    • They are not broken by heating or high salt concentration.
    • They can be broken by exposing them to strong acid or base for a long time at elevated temperature. Also, by some specific enzymes (digestive enzymes) .
  • Peptide bonds are rigid and planar bonds therefore they stabilize protein structure.
  • Peptide bond contains partial positive charge groups (polar hydrogen atoms of amino groups) and partial negative charge groups (polar oxygen atoms of carboxyl groups) .

Different Forms of Peptide Bond

  • Dipeptide = contains 2 amino acid units.
  • Tripeptide = contains 3 amino acid units.
  • Tetrapeptide = contains 4 amino acid units.
  • Oligopeptide = contains not more than 10 amino acid units.
  • Polypeptide = contains more than 10 amino acid units, up to 100 residues.
  • Macro peptides = made up of more than 100 amino acids.


Are Peptides Proteins?


Peptides are smaller than proteins. Traditionally, peptides are classified as molecules that consist of between 2 and 50 amino acids, whereas proteins are made up of 50 or more amino acids.

What Are Natural Peptides?


Peptides are found in all living organisms, and play a key role in biological activity of any sort. The peptides are biological molecules that occur naturally. Like proteins, peptides are naturally produced (synthesized) from transcriptions of a genetic code sequence, DNA.

Do Peptides Have Isoelectric Points?


The pH value at which the molecule bears no electric charge is the isoelectric point (pI) . This principle is particularly important for zwitterionic molecules including amino acids, peptides, and proteins. For an amino acid the isoelectric point is the amine and carboxyl group average pKa values.

What Are Biologically Active Peptides?


Bioactive peptides can be identified as specific portions of 2 to 20 amino acid proteins with beneficial biological effects, including antioxidant, anti-hypertensive, anti-adipogenic, antimicrobial and anti-inflammatory effects.

What Are Milk Peptides?


Milk peptides are produced during the fermentation of milk from milk proteins by enzymatic breakdown by digestive enzymes or by lactobacilli proteinases.

What Are Peptides?


  • A peptide is a chain of amino acids. In order to form the chain, two neighboring amino acid molecules, condense with the elimination of water and covalently connected. The bond connecting the two amino acids is an amide linkage herein called a peptide bond. A peptide bond is formed upon the loss of hydroxyl group from carboxy-terminus of one amino acid and hydrogen from the amino terminus of the second amino acid. As a result, resulting carbonyl group՚s carbon atom of one amino acid is directly bound to the nitrogen atom of a secondary amine of the second amino acid.
  • One amino acid loose hydrogen or and the other amino acid loose hydroxyl part. So, the leftover (residue) and not the complete amino acid is present in the peptide or protein. So, protein is said to contain not amino acids but only amino acid residues. Terminal amino acids of the peptides always have a free amino group (N-terminal) at one end and free carboxyl (C-terminal) group on the other end of the chain.
  • Based on the number of amino acids that have condensed together, they may be called dipeptide, tripeptide, oligopeptide, and polypeptide. Peptides having molecular weights below 10,000 are called polypeptide, and those having still higher molecular weight are called proteins.

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