Peptide bond

Peptide bond

Amino acids that make up proteins are bound by peptide bonds.

Chemistry

Keywords

peptide bond, amide bond, dipeptide, tripeptide, polypeptide, protein, C-terminus, N-terminus, amine group, carboxyl group, amino acid, glycine, alanine, organic side chain, water release, spatial structure, protein synthesis, enzyme, organic chemistry, biochemistry, chemistry

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Scenes

Structure of amino acids

  • glycine amino acid - There are 20 proteinogenic amino acids, one of them is glycine.
  • alanine amino acid - There are 20 proteinogenic amino acids, one of them is alanine.
  • amine group - -NH₂
  • carboxyl group - -COOH
  • alpha (α) carbon atom - A hydrogen atom, an amine group (-NH₂), a carboxyl group (-COOH) and an organic side chain are attached to the central carbon atom (the α carbon atom).
  • organic side chain - Amino acids differ in their organic side chains. In glycine, this side chain is a hydrogen (H) atom.
  • organic side chain - Amino acids differ in their organic side chains. In alanine, this side chain is a methyl group (-CH₃).

Peptide bond

  • water release
  • peptide bond - In organisms the formation of peptide bonds is catalised by enzymes.
  • C-terminus - The end of the molecule terminated by a carboxyl group (-COOH).
  • N-terminus - The end of the molecule terminated by an amine group (-NH₂).

Polypeptide

  • C-terminus - The end of the molecule terminated by a carboxyl group (-COOH).
  • N-terminus - The end of the molecule terminated by an amine group (-NH₂).

Animation

Narration

Proteins are composed of amino acids. Proteinogenic amino acids contain an alpha carbon atom, to which a hydrogen atom, a carboxyl group, an amine group and an organic side chain are attached. Amino acids are differentiated by their organic side chains.

Amino acid molecules can be linked together by peptide bonds. A peptide bond is a type of covalent bond formed between the carboxyl group of one amino acid molecule and the amine group of the other amino acid molecule in a dehydration reaction. In this reaction, the carboxyl group of one amino acid molecule releases a hydroxyl group, while the amine group of the other amino acid molecule releases a hydrogen ion. The hydroxyl group and the hydrogen ion form a water molecule, and a peptide bond is formed between the two amino acid molecules. The resulting molecule is called a dipeptide if it consists of two amino acid molecules. The end of the molecule terminated by a carboxyl group is called the C-terminus, while the end terminated by the amine group is called the N-terminus. That is, the molecule has a direction.

If further amino acid molecules attach, the resulting polypeptide chains, that is, protein molecules, can be of any length in principle. However, the proteins found in our bodies typically consist of a few hundred amino acid molecules. The attachment of these molecules, which is also called peptide synthesis, is catalysed by enzymes, and it takes place in the ribosomes.

Polypeptide chains can fold into complex shapes and play a variety of biochemical roles.

Related items

Amino acids

Amino acids are the monomers of proteins.

Secondary structure of proteins

Polypeptide chains are composed of amino acids and can appear in alpha-helix or beta-sheet form.

Structure of proteins

The structure and arrangement of polypeptide chains affects the spatial structure of proteins.

Alanine (C₃H₇NO₂)

A non-polar amino acid. L and D molecules are mirror images of each other.

Polymerisation of ethene

Polymerised ethylene is known as polyethylene, a type of plastic.

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