Amino acids- Properties, Functions, Sources

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The organic compounds that contain both the carboxyl and amino groups are Amino acids. So there are two functional groups present in this molecule they are amino (-NH2) and carboxyl groups (-COOH). Amino acid is a short form of the word alpha-amino carboxylic acid. Amino acids contain the elements- carbon, oxygen, nitrogen, and hydrogen. But in some amino acids, other elements such as sulphur and selenium are also present. Amino acids are the basic constituent of proteins. And proteins are formed when amino acids combine. Protein has many uses in the human body as well as in other organisms. Proteins act as a catalyst for many important reactions taking place in the cell.

What are Amino acids?

The organic compounds that contain carboxyl and amino as the two functional groups are amino acids. Amino acids are white crystalline solid and have a particular taste for each amino acid. While proteins are tasteless compounds, amino acids have sweet, bitter, and other tastes. So they also have properties which can give taste to food we eat. There are 20 amino acids. Some of them cannot be synthesized by our body and are given the name essential amino acids since we need to consume them through food. Apart from the nine essential amino acids all the other amino acids are synthesized in the cells present in our body itself and are given the name nonessential amino acids. These 20 amino acids that are essential and nonessential differ from each other in the side chain of the R or hydrocarbon group. Amino acids have important applications in the human body since they help in food digestion, repairing tissues, proper functioning of enzymes, promoting muscle growth, transportation of molecules, etc. By consuming foods that contain protein we get amino acids for the body. Some examples of amino acids are alanine, valine, phenylalanine, etc.

Structure of Amino acid

The basic structure of all the amino acids is the same. It consists of a central carbon that is the alpha carbon and in it, four different groups are attached. They are carboxyl, amino group, hydrogen, and R group. The group that is different in amino acids is the R group. All the other structural features are the same for all the amino acids. But for glycine the R group is hydrogen. The structure of Amino acids is as follows.

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Types of amino acids

They are mainly classified by the nutritionist based on their availability in the human body. And there is no impact on the structure and this classification. And the detailed explanation of the two amino acids is explained below.

  • Non-essential amino acids.

  • Essential amino acids.

Essential amino acids

The amino acid that would not be synthesized or produced by our body but is needed for the proper functioning of the human body is an essential amino acid. And it differs from organism to organism and also for children and adults. Example of essential amino acid is histidine, valine, etc.

Nonessential amino acids

These categories include the amino acids that are synthesized by the cells present in our body. They are produced by various metabolic processes happening in the body and also from other amino acids. Some examples of nonessential amino acids are alanine, cysteine, etc.

The structure of essential and nonessential amino acids is shown below.

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Properties of Amino acid

Physical properties

Amino acids are crystalline colourless organic compounds. They are commonly tasteless but have a sweet and bitter taste to some amino acids. They are ionic compounds and so they have a high melting point of approximately 300°C.

Chemical properties

Amino acids are polar molecules and will dissolve in water and ethanol. But they are not soluble in nonpolar solvents such as ether, benzene, etc. They are dipolar since they contain both acidic and basic functional groups. So it is a zwitterion. And also they can participate in chemical reactions which involve the use of the functional groups' carboxyl and an amino group.

List the essential and nonessential amino acids.

Examples of Essential and nonessential amino acids are shown below.














Glutamic acid








Aspartic acid


Functions of essential and nonessential amino acids

The functions of the compound amino acids are many they are a synthesis of porphyrin, synthesis of proteins, synthesis of plant hormones, synthesis of vitamins, etc.

Functions of some nonessential amino acids

  • Alanine: Helps in the removal of toxins present in the body. And also helps in maintaining immunity by helping in the production of lymphocytes.

  • Arginine: It will help in maintaining hormone balance, and is a precursor of Nitric oxide.

  • Asparagine: Helps in maintaining balance in the central nervous system and also helps in the development of neurons.

  • Aspartic acid: It is an important chemical compound and is associated with the active part of many enzymes.

  • Cysteine: One of the important components of beta keratin, which is essential for the nail, hair, and skin cells.

  • Glutamine: It helps in the proper digestion, and brain function of the human body.

  • Glycine: Helps in wound healing by assisting collagen production.

Functions of essential amino acids

Some of the functions of essential amino acids are given below.

  • Methionine: Helps in the reduction of fatty acids accumulating in the cell wall.

  • Leucine: Helps to maintain sugar level.

  • Lysine: Helps in the growth and development of bones by promoting calcium absorption.

  • Valine: It helps in the tissue growth in the human body.

  • Phenylalanine: Assist in the regulation of mood and proper functioning of the memory system.


Amino acids are chemical compounds that contain amino and carboxyl groups. In which the alpha carbon atom of amino acid contains amino, carboxyl, hydrogen, and R groups. For different amino acids, their basic structure is similar only differences exist in the R group. They are crystalline white-coloured compounds and some of which have a sweet and bitter taste. And are soluble in water but insoluble in benzene and ether. There are mainly two types of amino acids that are essential and nonessential amino acids. Essential amino acids need to be taken through our food while nonessential amino acids are synthesized in our body cells. They both play a great role in the proper functioning of the human body.


1. Which is the smallest amino acid structure?

The nonessential amino acid, glycine is the smallest among the amino acids. Since the R group present in glycine is hydrogen in the alpha carbon. Other groups are amino and carboxyl. While the essential amino acid Tryptophan is the largest.

2. Is there aromatic amino acid?

Yes. Tyrosine, phenylalanine, and Tryptophan are aromatic amino acids. They contain an aromatic group as the R group. And they are relatively nonpolar.

3. What happens if you take too many amino acids?

When someone intakes too much amino acid in their body, it will result in health problems. They are headaches, fatigue, upset stomach, nausea, etc. And at the peak low mood, loss of coordination, and sleep cycle problems will also occur.

4. How do amino acids become proteins?

In the cell, proteins are made by following complex chemical reactions. Amino acids join or link together using a peptide bond in proper order in the ribosome. The process is the translation and the compound thus obtained is also given the name polypeptide.

5. Why do proteins fold?

Proteins fold in the endoplasmic reticulum of the cell, in such a way that they can perform their functions properly. Proteins must be folded into a three-dimensional shape unless they won't work properly.


  • Muhammed Akram, Muhammed Asif, Muhammed Uzair Amino acids: A review article, 2011.

  • Rahat Ullah, Myeung Hoon Jo, Glycine the smallest amino acid, confers neuroprotection against D-galactose-induced neurodegeneration and memory impairment by regulating c- jun N-terminal kinase in the mouse brain, 2020.

  • Micheal J. Lopez, Shamim S. Mohiuddin Biochemistry essential amino acids, 2022.

  • Jay R. Hoffmann and Micheal J. Falvo Protein which is best? 2004.

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Updated on 13-Oct-2022 11:19:47