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

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What Are Peptides?

  • Peptides are naturally occurring short chains of amino acid monomers connected by amide bonds.
  • In other words, any substance which resembles the molecular structure of smaller proteins. Peptides include many antibiotics, hormones and other substances that involve in the biological functions of living beings.
  • Peptides are separated from proteins on the basis of size. Proteins are comprised of multiple polypeptides that are placed in a biologically functional way.
Peptides Are Naturally Occurring
  • There are many types of peptides; Di-peptide is the shortest peptides which consist of only two amino acids connected by one peptide bond.
  • A polypeptide is a continuous long and single peptide chain. Therefore, it can be stated that peptides belong to a broad category of biological polymers and oligomers.

Types & Classes of Peptides

These are categorized into several classes, based on their production type.

  • Milk Peptides: Formed when the digestive system breaks down a milk protein called Casein. They are also formed from proteinases arisen from lactobacilli during fermentation of milk.
  • Peptones: Peptones are produced during the proteolysis of animal milk or meat. Sometimes it also can be formed from vitamins, fats, metals and some salts. Peptones are useful in growing fungi and bacteria that are used in nutrient media.
  • Ribosomal Peptides: These are produced by translation (a process in which cellular ribosomes create proteins) of . To achieve mature form, they are often subjected to proteolysis. Some organisms like microcins (small bacteria) produce peptides as antibiotics. However, these peptides undergo post-translational modifications like hydroxylation, phosphorylation, sulfonation and glycosylation.
  • Non-ribosomal Peptides: Non-ribosomal Peptides are comprised of enzymes that are unique to each peptide, instead of the ribosome. Glutathione is the most common non-ribosomal peptide. These peptides have highly complex structures and are often cyclic.
  • Peptide Fragments: The fragments of proteins that are used to quantify or identify the source of protein are referred to as Peptide fragments.

Molecular Biology

  • The reason is that peptides help in the production of peptide antibodies in animals. These are used to create antibodies in mouse or rabbit against the specific protein.
  • Peptides are also used in the study of protein function, structure and also used in mass spectrometry. There are also Peptide hormones which are basically hormones with peptide molecules.

Applications of Peptides

  • Anti-Aging Creams: Many anti-aging creams contain different types of peptides. Most commonly used peptides are those that are obtained from ocean plants like sea jasmine, sea fennel and sea beet.
  • Anti-Microbial treatments: Antimicrobial peptides play a key role in treating the skin that is affected by injury, sun damage or acne lesions. Also proves that these are effective in restricting even the drug-resistant bacteria giving way to an array of possibilities in medical applications.
  • Body Imaging: Body scans work by sending dyes through the bloodstream that fluoresce when they come in contact with certain tissues. These imaging techniques can help doctors to detect life-threatening cancer at early stages.
  • Aspartame: The artificial sweetener with zero calories is found in many diet foods is a synthesized peptide. Aspartame is produced in labs which are 200 times sweeter than sugar.

Peptide Bond

  • A peptide is a Greek word which means “digested” . A peptide is a short polymer of amino acid monomers linked by an amide bond. A peptide bond is a chemical bond that is formed by joining the carboxyl group of one amino acid to the amino group of another. During this bond formation, there is a release of water () molecule.
  • A peptide bond is usually a covalent bond ( bond) and since the water molecule is eliminated it is considered as a dehydration process. Generally, this process occurs mostly between amino groups.

Peptide Bond Formation or Synthesis

A peptide bond is formed by a dehydration synthesis or reaction at a molecular level. As depicted in the figure given below, two amino acids bond together to form a peptide bond by the dehydration synthesis. During the reaction, one of the amino acids gives a carboxyl group to the reaction and loses a hydroxyl group (hydrogen and oxygen) .

Peptide Bond Formation or Synthesis
  • The other amino acid loses hydrogen from the group. The hydroxyl group is substituted by nitrogen thus forming a peptide bond. This is one of the primary reasons for peptide bonds being referred to as substituted amide linkages. Both the amino acids are covalently bonded to each other.
  • The newly formed amino acids are also called a dipeptide.
  • Formation of the peptide bond.
Peptide Bond Formation or Synthesis

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