Learn about the 9 essential amino acids, including their types, functions, and importance in the body. Discover interesting facts about each amino acid and how they contribute to overall health and well-being. Get the essential information you need to understand the role of amino acids in your diet and how to ensure you are getting enough of these crucial building blocks for protein synthesis.

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What are Amino Acids?

▪ Amino acids are the building blocks of proteins and are essential to the proper functioning of our bodies. They are organic compounds that contain an amine group (-NH2), a carboxyl group (-COOH), and a side chain or R-group that gives each amino acid its unique chemical properties.

▪ 20 different amino acids are commonly found in proteins, each with its unique side chain. Amino acids can be obtained from our diet or synthesized by our bodies. They are involved in various biological processes, including synthesising hormones, enzymes, and neurotransmitters.

▪ Amino acids are organic compounds containing an _
• Amino groups
• An acidic group

▪ Amino acids are the building blocks of Protein.
▪ Amino acids are the Substitution for Methanes.
▪ Amino acids are also called Alpha-amino acids.

▪ For the formation of Protein chains, the amino acids are joined together by forming Peptide Bond (CO – NH)

▪ These biomolecules are involved in various biological and chemical activities in the human body and are essential components for human growth and development. There are about 300 amino acids in nature.

Structure of Amino acids

▪ The general structure of an amino acid consists of an amino group (-NH2), a carboxyl group (-COOH), and a side chain or R-group that is specific to each amino acid. The amino and carboxyl groups are attached to the same carbon atom called the alpha carbon (α-carbon).

▪ In this structure, the alpha carbon is in the centre, the amino group is on the left, and the carboxyl group is on the right. The R-group or side chain is represented by “R” and is attached to the alpha carbon.

▪ The R-group can vary greatly in size, shape, and chemical properties, giving each amino acid its distinct characteristics. For example, the R-group of glycine is simply a hydrogen atom, while the R-group of tryptophan is a complex indole ring.

▪ The properties of the R-group also determine how the amino acid interacts with other molecules, such as in protein folding and binding to enzymes or other proteins.

Essential Amino Acids List

▪ 20 different amino acids are commonly found in proteins, but only 9 of them are considered essential amino acids.

▪ Essential amino acids are those that cannot be synthesized by the human body and must be obtained from the diet. Here is the list of essential amino acids:

1. Histidine
2. Isoleucine
3. Leucine
4. Lysine
5. Methionine
6. Phenylalanine
7. Threonine
8. Tryptophan
9. Valine

▪ These amino acids are essential for the proper functioning of our bodies, including the growth and repair of tissues, the synthesis of hormones, enzymes, and neurotransmitters, and the maintenance of immune function.

▪ They must be obtained from the diet, either through the consumption of protein-rich foods or through supplements.

Functions of Essential Amino Acids

Histidine

▪ This amino acid is essential for the production of histamine, a neurotransmitter that plays a vital role in immune response, digestion, sexual function, and regulating sleep-wake cycles. It is also critical in maintaining the myelin sheath, a protective barrier that surrounds nerve cells in the body.

Isoleucine

▪ Isoleucine, the third of the three branched-chain amino acids (BCAAs), plays a crucial role in muscle metabolism and is highly concentrated in muscle tissue. In addition to its role in muscle health, it is also important for immune function, haemoglobin production, and regulating energy levels in the body.

Leucine

▪ Leucine, another essential branched-chain amino acid (BCAA), plays a critical role in protein synthesis and muscle repair, much like valine. Additionally, it aids in regulating blood sugar levels, stimulating wound healing, and producing growth hormones in the body..

Lysine

▪ Lysine plays a significant role in various bodily functions, including protein synthesis, calcium absorption, and the production of hormones and enzymes. Additionally, it is essential for energy production, immune function, and the production of collagen and elastin, which are important for maintaining healthy skin and connective tissue.

Methionine

▪ This particular amino acid is crucial in the metabolism and detoxification processes within the body. Moreover, it is necessary for tissue growth and supports the absorption of essential minerals like zinc and selenium, which are vital to maintaining good health.

Phenylalanine

▪ The body converts this amino acid into several neurotransmitters, including tyrosine, dopamine, epinephrine, and norepinephrine. It is a critical component in the structure and function of proteins and enzymes and the production of other amino acids in the body.

Threonine

▪ This amino acid is a vital component of structural proteins like collagen and elastin, which are crucial in maintaining healthy skin and connective tissue. Additionally, it is involved in fat metabolism and supports immune function in the body.

Tryptophan

▪ Tryptophan is commonly linked to drowsiness and is a precursor to serotonin, a neurotransmitter that plays a key role in regulating appetite, sleep, and mood.

Valine

▪ This amino acid is among the three branched-chain amino acids (BCAAs) mentioned in this list. Its molecular structure has a chain branching off from one side, typical of BCAAs. Valine plays a crucial role in stimulating muscle growth and regeneration, and it also contributes to energy production in the body.

Major Facts about Amino Acids

 ▪ According to Hopkins, animals are unable to produce 7 out of the 20 different types of amino acids. This means that these 7 amino acids, known as essential amino acids for animals, must be obtained through the diet in order for animals to meet their nutritional requirements.

▪ These 7 amino acids are:

1. Leucine
2. Isoleucine
3. Valine
4. Tryptophan
5. Phenylalanine
6. Lysine
7. Methionine

▪ 9 essential amino acids for human adults cannot be produced by the body and must be obtained from the diet. These include :

1. Histidine
2. Isoleucine
3. Leucine
4. Lysine
5. Methionine
6. Phenylalanine
7. Threonine
8. Tryptophan
9. Valine

▪ In children, there are 10 essential amino acids as both arginine and histidine cannot be synthesized by their bodies. Therefore, the essential amino acids for children are the same as for adults plus arginine and histidine.

▪ Arginine and histidine are sometimes referred to as semi-essential amino acids because they are only essential in certain situations, such as during periods of growth and development.

▪ Aspartame is a synthetic polypeptide that is commonly used as an artificial sweetener.

▪ The amino acid dihydroxyphenylalanine is used in the treatment of Parkinsonism.

▪ Monosodium glutamate (MSG) is an amino acid used as a food additive to enhance flavour.

Types of Amino Acids Based on Nature

▪ Amino acids can also be classified based on their nature, as follows:

Non-essential Amino Acids

▪ The human body can synthesize these amino acids and therefore, do not need to be obtained from the diet. Examples include alanine, arginine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.

Essential Amino Acids

▪ The human body cannot synthesize these amino acids and must be obtained from the diet. Examples include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Conditionally Essential Amino Acids

▪ These amino acids are considered non-essential under normal circumstances but become essential under certain conditions, such as during periods of growth, illness, or stress. Examples include arginine and cysteine.

Glucogenic Amino Acids

▪ These amino acids can be converted into glucose through gluconeogenesis and contribute to energy production. Examples include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, methionine, proline, serine, and valine.

Ketogenic Amino Acids

▪ These amino acids can be converted into ketone bodies and contribute to energy production. Examples include leucine and lysine.

Sulphur-containing Amino Acids

▪ These amino acids contain sulfur in their side chains and are involved in forming disulfide bonds, which contribute to protein structure and stability. Examples include cysteine and methionine.

Types of Amino Acids Based on Properties

Amino acids can also be classified based on their properties, as follows:

Aromatic Amino Acids

▪ These amino acids have an aromatic ring in their side chain, which gives them unique properties.

▪ Examples include phenylalanine, tryptophan, and tyrosine.

Acidic Amino Acids

▪ These amino acids have a negatively charged carboxyl group in their side chain, which gives them an acidic property.

▪ Examples include aspartic acid and glutamic acid, Asparagine, and Glutamine.

Basic Amino Acids

▪ These amino acids have a positively charged amino group in their side chain, which gives them a basic property.

▪ Examples include lysine, arginine, and histidine.

Neutral Amino Acids

▪ These amino acids have a neutral charge in their side chain, which makes them hydrophobic or hydrophilic depending on their chemical structure.

▪ Examples include alanine, cysteine, glycine, isoleucine, leucine, methionine, proline, serine, threonine, and valine.

Importance of Amino Acids

▪ Amino acids are essential building blocks for proteins, vital to various biological processes in the body.

▪ Proteins play important roles in the structure and function of tissues and organs, the immune system, enzyme production, and hormone regulation, among other things.

▪ Amino acids also play critical roles in various physiological processes, such as metabolism, nutrient absorption, and the transportation of molecules within the body.

▪ Some amino acids act as neurotransmitters, which help regulate mood and behaviour, while others are involved in synthesising important molecules like haemoglobin and DNA.

▪ Furthermore, some amino acids have specific health benefits. For example, arginine has been shown to support healthy blood pressure levels, and tryptophan is involved in producing serotonin, a key neurotransmitter linked to mood regulation.

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