Serine Amino Acid Structure:Detailed Explanations

The scientists found twenty Amino acids in a human body which form proteins. Serine is one among these amino acids. In this article we see the Serine amino acid structure and facts about it.

Among the twenty Amino acids; some amino acid can be synthesized in human body, they are called non- essential amino acids. Serine is a non essential amino acid. The IUPAC name of Serine is 2-amino-3-hydroxypropanoic acid. It is a neutral amino acid with amino and carboxyl group in Serine amino acid structure.

 Amino acids are carboxylic acids. These acids have commonly two functional groups. One functional group is amino group and another functional group is Carboxyl group. Beside these the amino acid structure contains a side chain. This is written as ‘R’ in general in the structure.

Serine also has the amino (-NH2) group and the Carboxyl (-COOH) group. As a side chain Serine has a hydroxymethyl (-CH2OH) group. It is connected to central Carbon atom. There also an alpha (α) Hydrogen atom is present in the amino acid.

In an Amino acid structure; if the amino group and the carboxyl group are joined to the same Carbon atom, then the Amino acid is called alpha (α) – Amino acid. Serine is an alpha (α) Amino acid. In Serine structure both (-NH2) and (-COOH) groups are attached to the central Carbon atom.

Amino acids contains both (-NH2) and (-COOH) groups. (-COOH) is an acidic group and tends to donate the Hydrogen atom. This Hydrogen atom is accepted by the amino group present in the molecule as it has a basic nature. Hence Serine exists as a zwitter ion with both opposite charges.

serine amino acid structure
Zwitterion Serine amino acid structure

As a zwitter ion Serine has both positive and negative charges in the molecule. Both the opposite charges neutralized each other. As a whole the molecule has no charge. It is a neutral molecule.

The ionic form of the zwitter ion of the amino acid depends on the pH of the solution. At a strong acidic pH (pH<2), the ion accepts protons from solution and cationic forms are observed. In a strong basic pH (pH>11), the ion donates proton and anionic dorms are observed.

The amino acids have both charges present in the molecule. So serine is a good conductor of electricity for the zwitter ion structure in the solid phase.

Serine contains a hydroxyl group in the side chain. For this it is a polar amino acid. It can soluble in water as a result of the polarity. The Hydroxyl group forms strong Hydrogen bonding between the surrounding molecules. This makes the molecule hydrophilic in nature that means it produces a tendency to mix with water.

But Serine could not soluble in solvents that are not polar, like Benzene, Ether etc. Because these non- polar solvents could not able to dissolve the polar hydroxymethyl group or ionic part of Serine.

If a molecule has four different groups coordinate with a central Carbon atom; then the Carbon atom is called a chiral Carbon center. This means that the molecule is optically active in nature. It has ‘D’ and ‘L’ sttructures. These structures are mirror image to each other but not same.

Serine has four different groups around the central Carbon which are amino group, carboxyl group, hydroxymethyl group and a Hydrogen atom. So the amino acid is optically active molecule. It has two different structures like D- Serine and L- Serine.

For convention; the D- Serine molecule has the amino group (-NH2) to the right hand side of the central Carbon atom. The L- Serine molecule has the amino group to the left hand side of the central Carbon atom.

serine amino acid structure
L- Serine amino acid structure
serine amino acid structure
D- Serine ammino acid structure

Amino acids are the basic unit in the formation of protein structure. Protein molecules are formed by joining the Amino acids one after another. The bond formed between two Amino acids is called the Peptide bond. In the bond formation reaction one molecule of water is removed.

This joining of the Amino acids occurs systematically. The bond is formed between the carboxyl group of one Amino acid and amino group of another Amino acid next to it. In one side of the Peptide bond a free amino group is present, it is called N- terminus of the bond. On the other side a free carboxyl group is present, this end is called C- terminus of the bond.

For convention, the N- terminus of a Peptide bond is written to the left side and the C- terminus of the bond is written to the right side.

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