Amino Acids- Definition, Properties, Functions

Amino Acids All living organisms are made up of the same elements and compounds. If we analyse plant tissue, animal tissue or a microbial paste, several elements are observed. These elements include carbon, hydrogen, oxygen etc. If the analysis of non-living matter such as a piece of earth’s crust, similar chemicals are obtained. Amino Acids From all these analyses, it was observed that major elements are carbon and hydrogen as compared to other elements.

How To Analyse Chemical Composition

• Various biomolecules present in a living tissue can be studied by their chemical analysis.
• Take a living tissue and grind it in trichloroacetic acid using a mortar and pestle. After this, a thick slurry is obtained.
• When we strain this slurry through cheese cloth or cotton, it gives two fractions.-one is called filtrate or acid soluble pool and other is called retentate or acid insoluble pool.
• Acid soluble pool contains thousands of organic compounds.
• Acid insoluble pool contain proteins, nucleic acids, polysaccharides etc.
• The acid soluble pool contains chemicals with a small molecular mass of 18-800 daltons approximately. They are known as micromolecules or biomicromolecules. It includes amino acids, sugars, nucleotides etc.
• The acid-insoluble fraction contains organic compounds that have molecular weights in the range of ten thousands daltons and above. They are known as macromolecules or biomacromolecules. It includes polysaccharides, proteins and nucleic acids.

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Define Amino Acids

The word protein is derived from greek word “holding first place”. Proteins are made up of Carbon, hydrogen, oxygen and nitrogen. Proteins are polymers of amino acids. There are approximately 300 amino acids known to exist but only 20 types of amino acids are used in formation of proteins.

Proteins are heteropolymers of amino acids.

Some general properties of amino acids are-

• They are white crystalline solid substances.
• Have very high melting and boiling points.
• Mostly soluble in water and alcohol (polar solvents); but insoluble in nonpolar solvents(benzene)
• Amino acids are bitter, sweet or tasteless.

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Structure Of Amino Acids

• Amino acids contain an amino group and a carboxylic group on the same carbon, that is, the alpha-carbon. That is why they are known as alpha amino acids.

• Amino acids are substituted methanes.
• They are amphoteric in nature as they contain one acidic and one alkaline group.
• Due to their amphoteric nature, they form zwitterion.
• At isoelectric point amino acids carry net charge as zero and they will not move in an electric field. So, zwitterion is formed at isoelectric point.

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List Of 20 Amino Acids

Essential And Non-Essential Amino Acids

• Out of 20 amino acids, 10 amino acids are not synthesised in the body of animals so they must be present in the diet. These are called essential amino acids. It includes Threonine, Valine, Leucine, Isoleucine, Lysine, Methionine, Phenylalanine, Tryptophan, Arginine, and Histidine.

Note:  Arginine and Histidine are semi-essential; while others are essential.

• 10 amino acids are synthesised in the animal body so these are called non-essential amino acids. For example, Glycine, Alanine, Serine, Cysteine, Aspartic acid, Glutamic acid, Asparagine, Glutamine, Tyrosine, Proline.

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Classification Of Amino Acids

Amino acids are classified based on the number of carboxylic groups and amino groups.

Sources Of Amino Acids

• Amino acids are essential for carrying out a variety of biological and chemical processes in different parts of the human body such as synthesis and repair of tissues, the production and function of enzymes, food digestion, the movement of molecules, etc.
• Only a small number of amino acids, known as non-essential amino acids, can be produced by the body. Other amino acids must be included in our diet.
• Plant-based foods such as beans, broccoli, beetroots, pumpkin, cabbage, chia seeds, oats, almonds, dry fruits, peas, carrots, cucumber, whole grains, peanuts, legumes, green leafy vegetables, onions, soybeans, lentils, etc. are sources of amino acids.
• Apples, bananas, berries, figs, grapes, melons, oranges, papaya, pineapple, and pomegranates are among the fruits high in amino acids.

Functions Of Amino Acids

Some Important Points On Amino Acids

• Tryptophan is the most complex amino acid and is required for synthesis of indole acetic acid (IAA). IAA, also known as auxin, is a plant growth regulator.
• Tyrosine is required for the synthesis of melanin pigment, thyroxine hormone, adrenaline and nor-adrenaline hormone.
• Proline amino acids contain an imine group instead of amino group.so, it is also known as imino acids.
• Cysteine and methionine are sulphur containing amino acids.
• Tyrosine, tryptophan and phenylalanine are aromatic amino acids.
• Glycine is the simplest amino acid.
• Some amino acids do not participate in protein synthesis. They are known as non-protein amino acids. For example, citrulline, ornithine etc.