Difference Between Essential and Nonessential Amino Acids

Main Difference – Essential vs Nonessential Amino Acids

Amino acids can be described as the building blocks for proteins, enzymes, hormones, transport molecules, neurotransmitters and other organic compounds that are mainly present in living organisms. An amino acid is a relatively small nitrogen-containing molecule, and 22 amino acids can be identified in nature. Out of these 22 amino acids in nature, 20 are present in the human body. Biochemically, these amino acids can be subdivided into two groups; essential and nonessential amino acids. Non-essential amino acids can be synthesized by the human body whereas essential amino acids must be obtained from the daily diet. This is the key difference between essential and nonessential amino acids.

This article explores,

1. What are Essential Amino Acids?
     – Synthesis, Sources, Types

2. What are Non-essential Amino Acids?
     – Synthesis, Sources, Types

3. What is the difference between Essential and Nonessential Amino Acids?

What are Essential Amino Acids

All human being, including infants, are not capable of synthesizing 9 out of the 20 amino acids required by living cells and tissues. They must be obtained from dietary sources. They are known as essential amino acids.

What are Nonessential Amino Acids

All human being, including infants, are capable of synthesizing 10 out of the 20 amino acids required by living cells and tissues. They are known as non-essential amino acids.

Difference Between Essential and Nonessential Amino Acids

Essential and nonessential amino acids may have significantly different functional characteristics. These can be categorised into following subgroups,

Synthesis in the Human Body

Essential amino acids cannot be synthesized by the human body.

Nonessential amino acids can be synthesized by the human body.

Obtained from Daily Diet

Essential amino acids must be obtained from the daily diet as that cannot be synthesized by the human body. Deficiency of essential amino acid can be identified as protein-energy malnutrition, which can noticeable as marasmus or kwashiorkor. This deficiency can affect the functions of all of the body’s organs, including the brain function and the immune system, consequently increasing the risk of infection. Rich dietary sources of essential amino acids are meat, poultry, egg, cheese, milk, soya bean, tofu, etc.  

Nonessential amino acids can be synthesized by the human body and the synthesis is mainly dependent on the availability of precursors and other vital nutrients, such as vitamins. Therefore, a shortage of a required amino acid precursor or an essential nutrient can create a dispensable amino acid “conditionally essential.” For example, although glycine is  categorised as a nonessential amino acid, the human body should have an adequate amount of vitamin B6 and an enzyme called serine hydroxymethyltransferase to produce glycine. If the human body is deficient in vitamin B6, the body cannot produce glycine, which then must be obtained from the daily diet.

Alternative Names

Essential amino acids are known as indispensable amino acids.

Nonessential amino acids are known as dispensable amino acids.

Examples

Essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Nonessential amino acids: alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine.

Number of Amino Acids

Essential amino acids: Adults cannot synthesise 9 amino acids and infants cannot synthesise 10 amino acids.

Nonessential amino acids: Adults can synthesise 11 amino acids including Arginine, but infants and young children cannot create Arginine enough to meet their metabolic requirements.

Arginine

In conclusion, amino acids are used to produce proteins, neurotransmitters and hormones in animals and plant creatures. There are 22 different amino acids having different chemical structures, and each protein consists of 50 to 2,000 amino acids that are connected together in a specific sequence according to genetic instructions. These amino acids are divided into two categories: essential and nonessential, based on the ability to synthesis by the human body.

References:

Imura K, Okada A (1998). Amino acid metabolism in paediatric patients. Nutrition. 14 (1): 143–8.

J D Kopple and M E Swendseid (May 1975). Evidence that histidine is an essential amino acid in normal and chronically uremic man. J Clin Invest. 55 (5): 881–891.

Reeds PJ (1 July 2000). Dispensable and indispensable amino acids for humans. J. Nutr. 130 (7): 1835S–40S.

ürst P, Stehle P (1 June 2004). What are the essential elements needed for the determination of amino acid requirements in humans? Journal of Nutrition. 134 (6 Suppl): 1558S–1565S.

Young VR (1994). Adult amino acid requirements: the case for a major revision in current recommendations. J. Nutr. 124 (8 Suppl): 1517S–1523S.

Image Courtesy: 

NEUROtiker (Public Domain) via Commons Wikimedia

Wiremu Stadtwald Demchick (CCo) via Commons Wikimedia

Lizziechka (Public Domain) via Commons Wikimedia 

“L-arginine ethyl ester” By Edgar181 (talk) – Own work (Public Domain) via Commons Wikimedia

ncG1vNJzZmiolZm2oq2NnKamZ5Ses6ex0Z6lnJ1dl7K1w8SepWado6iyr8DImqNmmZ6Zeq%2B7zZ6qrJ2eqbaiuIyapKKmn2KupLXDrGY%3D