Amino Acids

What is an Amino acid?

“Amino Acids are the organic compounds that combine to form proteins, hence they are referred to as the building components of proteins. These biomolecules are involved in several biological and chemical functions in the human body and are the necessary ingredients for the growth and development of human beings. There are about 300 amino acids that occur in nature.”

Table of Contents:

Amino acids are organic compounds containing the basic amino groups (-NH2) and carboxyl groups (-COOH). The ingredients present in proteins are amino acids. Both peptides and proteins are long chains of amino acids. Altogether, there are twenty amino acids, which are involved in the construction of proteins.

List of 20 Amino acids with the chemical formula

Listed below are the names of twenty amino acids along with their chemical formula.

Alanine C3H7NO2 Leucine C6H13NO2
Aspartic Acid C4H7NO4 Lysine C6H14N2O2
Asparagine C4H8N2O3 Methionine C5H11NO2S
Arginine C6H14N4O2 Proline C5H9NO2
Cytosine C4H5N3O Phenylalanine C9H11NO2
Cysteine C3H7NO2S Serine C3H7NO3
Glycine C2H5NO2 Tyrosine C9H11NO3
Glutamine C5H10N2O3 Threonine C4H9NO3
Histidine C6H9N3O2 Tryptophan C11H12N2O2
Isoleucine C6H13NO2 Valine C5H11NO2

General properties of Amino acids

      • They have a very high melting and boiling point.
      • Amino acids are white crystalline solid substances.
      • In taste, few Amino acids are sweet, tasteless, and bitter.
      • Most of the amino acids are soluble in water and are insoluble in organic solvents.

Essential and Non-essential Amino acids

Out of 20 amino acids, our body can easily synthesize a few on its own, which are called non-essential amino acids. These include alanine, asparagine, arginine, aspartic acid, glutamic acid, cysteine, glutamine, proline, glycine, serine, and tyrosine.

Apart from these, there are other nine amino acids, which are very much essential as they cannot be synthesized by our body. They are called essential amino acids, and they include isoleucine, histidine, lysine, leucine, phenylalanine, tryptophan, methionine, threonine, and valine.

Also read about Proteins

Structure of Amino acids

Structure of Amino Acids

The general structure of Amino acids is H2NCH RCOOH, and it can be written as:



H2N – – C – – H



There are 20 naturally occurring amino acids and all have common structural features – an amino group (-NH3+), a carboxylate (-COO-) group and a hydrogen-bonded to the same carbon atom. They differ from each other in their side-chain called the R group. Each amino acid has 4 different groups attached to α- carbon.

These 4 groups are:

      • Amino group,
      • COOH,
      • Hydrogen atom,
      • Sidechain (R).

Structure of 20 Amino acids with their chemical formula

Here is the structure of twenty amino acids with their chemical formula.

Amino Acid Structure and Molecular formula

Sources of Amino acids

Sources of Amino Acids

Amino acids play an important role in performing several biological and chemical functions in different parts of our body, including building and repairing the tissues, the formation and function of enzymes, food digestion, the transportation of molecules, etc. Our body can synthesize only certain amino acids and the rest of the amino acids which are called essential amino acids should be supplied through protein-rich foods in our daily diet.

Foods rich in amino acids include plant-based products like broccoli, beans, beetroots, pumpkin, cabbage, nuts, dry fruits, chia seeds, oats, peas, carrots, cucumber, green leafy vegetables, onions, soybeans, whole grain, peanuts legumes, lentils, etc. Fruits rich in amino acids are apples, bananas, berries, figs, grapes, melons, oranges, papaya, pineapple, and pomegranates. Other animal products include dairy products, eggs, seafood, chicken, meat, pork etc.

Amino Acids

Functions of Amino acids

      • Functions of Essential Amino acids
        • Phenylalanine helps in maintaining a healthy nervous system and in boosting memory power.
        • Valine acts as an important component in promoting muscle growth.
        • Threonine helps in promoting the functions of the immune system.
        • Tryptophan is involved in the production of vitamin B3 and serotonin hormones. This serotonin hormone plays a vital role in maintaining our appetite, regulating sleep and boosting our moods.
        • Isoleucine plays a vital role in the formation of haemoglobin, stimulating the pancreas to synthesize insulin, and transporting oxygen from the lungs to the various parts.
        • Methionine is used in the treatment of kidney stones, maintaining healthy skin and also used in controlling invade of pathogenic bacteria.
        • Leucine is involved in promoting protein synthesis and growth hormones.
        • Lysine is necessary for promoting the formation of antibodies, hormones, and enzymes and in the development and fixation of calcium in bones.
        • Histidine is involved in many enzymatic processes and in the synthesizing of both red blood cells (erythrocytes) and white blood cells (leukocytes).
      • Functions of Non-Essential Amino acids
        • Alanine functions by removing toxins from our body and in the production of glucose and other amino acids.
        • Cysteine acts as an antioxidant and provides resistance to our body; it is important for making collagen. It affects the texture and elasticity of the skin
        • Glutamine promotes a healthy brain function and is necessary for the synthesis of nucleic acids – DNA and RNA.
        • Glycine is helpful in maintaining the proper cell growth, and its function, and it also plays a vital role in healing wounds. It acts as a neurotransmitter.
        • Glutamic acid acts as a neurotransmitter and is mainly involved in the development and functioning of the human brain.
        • Arginine helps in promoting the synthesis of proteins and hormones, detoxification in the kidneys, healing wounds, and maintaining a healthy immune system.
        • Tyrosine plays a vital role in the production of the thyroid hormones -T3 and T4, in synthesizing a class of neurotransmitters and melanin, which are natural pigments found in our eyes, hair, and skin.
        • Serine helps in promoting muscle growth and in the synthesis of immune system proteins.
        • Asparagine is mainly involved in the transportation of nitrogen into our body cells, formations of purines and pyrimidine for the synthesis of DNA, the development of the nervous system and improving our body stamina.
        • Aspartic acid plays a major role in metabolism and in promoting the synthesis of other amino acids.
        • Proline is mainly involved in the repairing of the tissues in the formation of collagen, preventing the thickening and hardening of the walls of the arteries (arteriosclerosis) and in the regeneration of new skin.

Deficiency of Amino acids

As mentioned above, amino acids are the building blocks of proteins and proteins play a fundamental role in almost all life processes. Therefore, it is necessary to include all nine essential amino acids in our daily diet to maintain a healthy and proper function of our body. The deficiency of amino acids may include different pathological disorders, including:

      • Edema.
      • Anemia.
      • Insomnia.
      • Diarrhea.
      • Depression.
      • Hypoglycemia.
      • Loss of Appetite.
      • Fat deposit in the liver.
      • Skin and hair related problems.
      • Headache, weakness, irritability, and fatigue.

Also refer-Deficiency Diseases

Also Read: Amino Group

Stay tuned with BYJU’S to learn more about amino acids, their functions and other Biomolecules at BYJU’S Biology.

Frequently Asked Questions


Define amino acids.

In simpler terms, Amino acids are organic compounds containing the basic amino groups (-NH2) and carboxyl groups (-COOH).

Give examples of essential amino acids.

Essential amino acids cannot be synthesized and hence must come from our diet. The 9 essential amino acids are – Isoleucine, histidine, lysine, leucine, phenylalanine, tryptophan, methionine, threonine, and valine.

Why are amino acids called amphoteric?

Amino acids have both acidic and basic properties. This is why they are amphoteric. The predominant form of the amino acid is based on the pH of the solution.

What is zwitterion?

The actual structure of amino acids is ionic and depends on pH even though we usually write amino acids with a carboxyl group and amino group. The carboxyl group gives up a proton, donating a carboxylate ion. The amino group is protonated to an ammonium ion. This structure is referred to as a zwitterion or dipolar ion.

Give an example of a transport protein and mention its function.

Haemoglobin is a transport protein. It is involved in the transportation of oxygen to the cells.

Name a sulphur-containing amino acid.

Methionine and cysteine are sulphur-containing amino acids.

Are amino acids and proteins same?

Proteins are composed of monomers called amino acids. A protein comprises one or more polypeptides, which are individual linear chains of amino acids.

How many amino acids are found in proteins?

20 basic amino acids are used to make both plant and animal proteins.

What are protein amino acids?

Protein amino acids are called alpha amino acids.

Name the amino acid found in protein structure.

Protein structures contain the four amino acids asparagine, aspartic acid, threonine, and methionine, each of which has four carbon atoms.
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  1. I’m studying for the MCAT this was very thorough I truly enjoyed it thank you

  2. This information very much pertinent for the concept