branched-chain amino acids and a part of essential amino acids
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What Are the Different Chemical Structures of Amino Acids?

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You will find many articles on amino acids and their benefits for human health, but let’s understand their chemical structure in this article to learn more about them.

What are amino acids?

Popularly known as the building blocks of proteins, amino acids are the organic compounds involved in various human bodily functions like neurotransmission, protein synthesis, maintaining the healthy nervous system, improving the immune system, and much more.

Surprisingly, there are about 500+ amino acids found in nature, but, only 20 are genetically coded till date; hence the structure and functions of solely these 20 amino acids are determined by scientists.

We will check out the different chemical structures of amino acids in the next sections, but for now, let’s understand the general idea of the basic chemical structure of any amino acid.

General Chemical structure of amino acids

As seen above, amino acids are the organic compounds that build up proteins. Amino acids are made up of four components

  • An amine groups
  • A carboxylic group
  • Hydrogen
  • And an R group

Facts regarding chemical structures of amino acids

  • All these four components are attached to a single carbon atom positioned at the centre of the structure. This makes the central single carbon atom of all the amino acids chiral (except glycine, which we will find why while discussing glycine’s chemical structure). This chiral carbon is also known as alpha carbon.
  • Amino acids can form stereoisomers which surround this particular chiral carbon. This divides the amino acids into two types of isomers, called L and D amino acids.
  • L amino acids are the stereoisomers whose amine group is on the left side in the fisher projection. They are essential in all types of functions in the cells. They are also a necessary part of proteins.
  • D amino acids are the second type of isomers occurring in nature. The amine group of these D isomers are on the right side of the fisher projection. These D amino acids are not included within the proteins by the cells.
  • The amine group (NH2) and the carboxylic group (-COOH) form the basic structure of amino acids.
  • The R group is specific for each amino acid. In fact, different amino acids can be identified and differentiated from each other with this R group’s help. This R group is vital in classifying amino acids into different types and defining their polarity, optical activity and much more.
  • You should also know that the carboxyl group of one molecule reacts with the amine group of other molecules, forming a chemical bond between the two molecules. This releases out a water molecule during the reaction. This particular chemical bond is the peptide bonds amino acids form to combine as a polypeptide or protein.

Let’s see the structures of all the 20 amino acids in the next section.

Chemical structures of amino acids?

1. Alanine – ala – A

Alanine is a nonessential amino acid that occurs in high levels in its free state in plasma. The chemical structure is C3H7NO2.

2. Arginine – arg – R

Arginine is an essential amino acid in juvenile humans, and it is a complex amino acid, often found at the active site in proteins. The chemical structure is C6H14N4O2

3. Asparagine – asn – N

Asparagine is a nonessential amino acid in humans and is a beta-amido derivative of aspartic acid. The chemical structure is C4H8N2O3

4. Aspartic acid – asp – D

Aspartate amino acid or Aspartic acid is a nonessential amino acid, meaning that mammals readily and naturally synthesize it. The chemical structure is C4H7NO4

5. Cysteine – cys – C

Cysteine is a nonessential amino acid and is one of the few amino acids that contains Sulphur. The chemical structure is C3H7NO2S.

6. Glutamine – gln – Q

Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. The chemical structure is C5H10N2O3

7. Glutamic acid – glu – E

Glutamic acid is a nonessential amino acid, which is used as an excitatory neurotransmitter. Its chemical structure is C5H9NO4

8. Glycine – gly – G

It is the nonessential amino acids which are used as a neurotransmitter. R group for glycine is just a hydrogen atom. Which is why there is this duplication of atoms. And so, glycine is the only amino acid that does not have a chiral carbon. The chemical structure C₂H₅NO₂

9. Histidine – his – H

It is known as a “semi-essential amino acid” because it is nonessential in adults, but essential in infants’ diet. Its chemical structure is C6H9N3O2

10. Isoleucine – ile – I

It is one of the three branched-chain amino acids and a part of essential amino acids. The chemical formula is C6H13NO2

11. Leucine – leu – L

It is one of the three branched-chain amino acids and a part of essential amino acids. The chemical formula is C6H13NO2

12. Lysine – lys – K

It is an essential amino acid with the chemical formula C6H14N2O2

13. Methionine – met – M

It is an essential amino acid with the chemical formula C5H11NO2S

14. Phenylalanine – phe – F

Phenylalanine is an essential α-amino acid with the chemical formula C9H11NO2

15. Proline – pro – P

Proline an organic acid classed as a does not contain the amino group proteinogenic acid amino  although it . The chemical formula is C5H9NO2

16. Serine – ser – S

It is a nonessential amino acid in humans with chemical formula C3H7NO3

17. Threonine – thr – T

It is an essential amino acid with the chemical formula C4H9NO3

18. Tryptophan – trp – W

It is an essential amino acid with the chemical formula C11H12N2O2

19. Tyrosine – tyr – Y

Is a nonessential amino acid produced in the body from another amino acid phenylalanine. The chemical formula is C9H11NO3

20. Valine – val – V

It is one of the three branched-chain amino acids and a part of essential amino acids. The chemical formula is C5H11NO2

Summary

The 20 amino acids that are important for organisms have a common chemical basic structure in the form of the amine & carboxylic group. But they differ from each other due to the different and unique R groups attached to them.

Amino acids can be identified due to these specific R groups. The structure of amino acids is important with respect to their role in performing vital functions in the human body.

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