Essential vs. Non-Essential Amino Acids: What’s the Difference?

Amino acids are the basic components of life, having a very great influence on our body processes. They are small structural molecules that can easily bond together in many configurations, and create proteins for growth, repair and health. There are twenty standard amino acids which differ from each other in properties and functions, and they are divided into essential and non-essential amino acids. This post will also discuss the basic composition of amino acids, the various categories of amino acids, and their benefits to human health. Amino acids are the backbone of nutrition and thus essential for any laymen, as well as experts, to understand.

Amino acids are the building components of proteins. The sequence of nucleotides in the gene that encodes a protein determines its precise amino acid composition and sequence. Proteins’ biological activity is determined by the chemical characteristics of their amino acids. Amino acids are essential for all cells’ growth, repair, and maintenance. Proteins’ biological activity is determined by the chemical characteristics of their amino acids. Proteins catalyze practically all events in living cells and regulate virtually all biological functions.

Basic Structure of Amino Acid

An amino acid has amino and carboxylic acid functional groups. A peptide bond is formed when the N-terminal amino group (-NH2) and C-terminal carboxyl group (-COOH) attach to the -carbon. Polypeptides are chains of amino acids, and a big polypeptide is considered a protein. Human serum has approximately 100-150 amino acids in its polypeptide chains. The chemical composition of the R group (side chains) distinguishes amino acids from each other.

Metabolism of amino acids

About half of the 20 amino acids required by humans cannot be produced quickly enough to maintain growth; therefore, they must be obtained from food. These nutritionally important amino acids must be obtained through the diet in the form of proteins. The essential amino acids include arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The body can manufacture ten amino acids: alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.

Tyrosine is synthesized from phenylalanine, so if the diet lacks phenylalanine, tyrosine will be required as well. Humans lack all of the enzymes required for complete amino acid production. Under normal conditions, proteolytic enzymes like pepsin and trypsin thoroughly digest food proteins to their constituent amino acids. Amino acids are then swiftly absorbed from the intestine into the bloodstream, where they become part of the body’s amino acid pool. The regular breakdown of the body’s proteins also releases amino acids.

Amino acids are mostly used to synthesize body proteins, such as plasma, intracellular, and structural proteins. Amino acids are also utilized to make nonprotein nitrogen molecules such purines, pyrimidines, porphyrins, creatine, histamine, thyroxine, epinephrine, and the coenzyme NAD. In addition, protein accounts for 12%-20% of total daily body energy requirements. The amino group is removed from amino acids via deamination or transamination. The resulting ketoacid can enter the same metabolic route as carbs and lipids. Glucogenic amino acids produce glucose precursors such as pyruvate and citric acid cycle intermediates. Examples include alanine (deaminated to pyruvate), arginine (converted to alpha-ketoglutarate), and aspartate (converted to oxaloacetate). Ketogenic amino acids produce ketone bodies. They are degraded to acetyl-CoA or acetoacetyl-CoA (for example, leucine or lysine), and some amino acids are both ketogenic and glucogenic. The liver’s urea cycle converts the ammonium ion produced during amino acid deamination into urea.

Essential Amino Acids

Arginine (Arg)

Arginine, a complex amino acid with an amine-containing side chain, is commonly found near catalytic sites in proteins and enzymes. Arginine is essential for cell division, wound healing, protein synthesis, immunity, and hormone release. Arginine is needed to produce urea, which removes harmful ammonia from the body. It also aids in the creation of creatine, which is then degraded to creatinine, a waste product eliminated by the kidney.

Histidine (His)

Histidine’s imidazole side chain makes it one of the most basic amino acids (by pH). It is the direct precursor to histamine, a protein implicated in the immunological response. Histidine contributes carbon atoms to the creation of purines, one of the two nitrogen bases found in DNA and RNA. Histidine is essential for tissue growth and repair, as well as the protection of nerve cells through myelin sheaths. Additionally, it promotes the production of red and white blood cells and protects against heavy metal toxicity. Histamine promotes gastrin secretion and catalyzes specific enzymes.

Isoleucine (Ile)

Isoleucine, a branched-chain amino acid, is essential for muscular tissue, skin, and bone health. Isoleucine contributes to hemoglobin synthesis, blood glucose regulation, and energy maintenance.

Leucine (Leu)

Leucine, like valine and isoleucine, is a branched-chain amino acid. Leucine is the second most prevalent amino acid found in protein, following glycine. Combining leucine with valine and isoleucine promotes muscle, skin, and bone healing, aids in surgery recovery, and decreases blood glucose levels. Leucine is required for healthy baby growth and nitrogen balance in adults.

Lysine (Lys)

• Lysine is classified as one of the three basic amino acids due to its net positive charge.
• Lysine promotes antibody formation and reduces lipid levels.
• Lysine is essential for child growth and bone formation, as well as maintaining a healthy nitrogen balance in adults.
• Lysine is essential for calcium absorption and conservation, as well as the synthesis of collagen, a key component of cartilage and connective tissue.

Methionine (Met)

Methionine is the first amino acid added to the N-terminal of all proteins, initiating messenger RNA translation.3 Methionine is a sulfur-rich nutrient essential for proper metabolism and growth. Methionine helps break down lipids, detoxify heavy metals, reduce muscle weakness, and prevent brittle hair. Methionine combines with adenosine triphosphate to synthesize essential chemicals like adrenaline and choline.

Phenylalanine (Phe)

Phenylalanine is classed as a nonpolar amino acid due to the hydrophobicity of its benzyl sidechain. It has numerous benefits, including increased alertness and vigor, improved mood, reduced pain, improved memory and learning, and treatment for arthritis and depression. The brain uses phenylalanine to make norepinephrine, a neurotransmitter that sends messages between nerve cells. Phenylalanine crosses the blood-brain barrier via an active transport channel and, in high concentrations, inhibits serotonin synthesis. Aspartame, a popular sugar substitute, contains phenylalanine. Phenylalanine facilitates the production of other amino acids.

Threonine (Thr)

Threonine, an alcohol-containing amino acid, is essential for the production of protein, collagen, elastin, and tooth enamel. It also plays a crucial role in neurotransmitter generation and nervous system health. Threonine promotes healthy protein balance and supports liver function, metabolism, and assimilation.

Tryptophan (Trp)

Proteolytic enzymes break down proteins and produce tryptophan. Tryptophan is a precursor to serotonin and melatonin, both neurohormones and potent antioxidants. Tryptophan is a natural relaxant that relieves sleeplessness, anxiety, and sadness. It treats migraine headaches, promotes weight loss by lowering hunger, and manages hyperactivity in youngsters.

Valine (Val)

Valine is another branched-chain amino acid found in fibrous protein in the body. Valine is essential for muscle metabolism and coordination, tissue regeneration, and maintaining nitrogen balance. Muscle tissue uses it for energy. Valine is used to treat physical, mental, and emotional issues, sleeplessness, anxiety, and liver/gallbladder disorders.

Nonessential Amino Acids

Alanine (Ala)

Alanine, a simple amino acid, contributes to the breakdown of glucose for energy production.
Alanine is derived from the degradation of DNA or the dipeptides anserine and carnosine, as well as the conversion of pyruvate, a key component in carbohydrate metabolism. Alanine aids in nitrogen transfer from peripheral tissues to the liver, reduces toxic substances released into muscle cells during protein breakdown for energy, and strengthens the immune system by producing antibodies.

Asparagine (Asn)

• Asparagine, the first amino acid discovered, was initially extracted in 1806 from asparagus juice.
• Asparagine is a key amino acid in nitrogen transport and is often found in abundance.
• Asparagine, the beta-amide of aspartic acid, is produced from aspartic acid and ATP.
• Asparagine primarily converts amino acids by amination (introducing an amine group into an organic molecule) and transamination (converting an amino acid to an alpha-ketoacid).
• Asparagine is essential for the nervous system and helps produce ammonia.

Aspartic Acid (Asp)

• Aspartic acid is alanine with one of its hydrogens replaced by a carboxylic acid group.
• Aspartic acid is essential for metabolism in the citric acid cycle, helping to build other amino acids and metabolites.
• Aspartic acid is used to manufacture many amino acids, including asparagine, arginine, lysine, methionine, threonine, isoleucine, and nucleotides.
• Aspartic acid is a urea cycle molecule that contributes to gluconeogenesis, which produces glucose from non-sugar carbon sources.

Cysteine (Cys)

• Cysteine is considered a nonessential amino acid, however it may be essential for babies, the elderly, and those with metabolic illnesses or malabsorption syndromes.
• Cysteine is a crucial structural and functional component of various proteins and enzymes.
• Cysteine is called after cystine, which is an oxidized dimer.
• Cysteine is a potentially hazardous substance that is catabolized in the gastrointestinal system and bloodstream. In contrast, cysteine is absorbed as cystine, which is more stable in the gastrointestinal tract.
• Cystine travels to cells and is degraded to two cysteine molecules upon entrance.
• Cysteine is employed in various industries, including food, pharmaceuticals, and personal care. Flavor manufacturing is one of its most significant applications.

Glutamic Acid (Glu)

• Glutamic acid is made from a variety of amino acids, and when an amino group is added to glutamic acid, it generates the essential amino acid glutamine.
• Glutamic acid is one of only two amino acids with a net negative charge (by pH), making it a highly polar molecule.
• Glutamic acid has been related to epileptic seizures; it is a neurotransmitter, plays a key role in sugar and fat metabolism, and aids in the movement of potassium into spinal fluid.
• Glutamic acid is found in a wide range of foods and is responsible for one of the five basic flavors of the human palate (umami).
• Glutamic acid is commonly employed as a food additive and flavor enhancer in the form of its sodium salt, monosodium glutamate (MSG).

Glutamine (Gln)

• Glutamine is the most prevalent amino acid in the body and plays a greater role in metabolic processes than any other.
• Glutamine accounts for more than 61% of skeletal muscle tissue.
• Glutamine is converted to glucose when more glucose is needed for energy and helps with immunological function.
• Glutamine helps to maintain the body’s acid/alkaline balance, fuels a healthy digestive tract, and serves as the foundation for the creation of RNA and DNA. Studies have indicated that glutamine can help treat major illnesses, damage, trauma, burns, and cancer treatment-related adverse effects, as well as wound healing in postoperative patients.
• Glutamine is also sold as a supplement for muscle growth in weightlifting and bodybuilding. Glutamine delivers ammonia, the harmful metabolic consequence of protein breakdown, to the liver, where it is transformed into less toxic urea and ultimately eliminated by the kidneys.

Glycine (Gly)

• Glycine is the simplest amino acid synthesized in the body, and it is the only one that is not optically active because it lacks stereoisomers.
• Glycine is required for the synthesis of nucleic acids, bile acids, proteins, peptides, purines, ATP, porphyrins, hemoglobin, glutathione, creatine, bile salts, glucose, glycogen, and other amino acids.
• The liver employs glycine to help with chemical detoxification and bile acid production.
• Glycine has a sweet taste and is used as a sweetener or flavor enhancer.
• Glycine is an inhibitory neurotransmitter in the central nervous system (CNS), a metal complexing agent, slows muscle degeneration, increases glycogen storage, and promotes healing.

Proline (Pro)

The body converts proline into hydroxyproline, which is then incorporated into collagen, tendons, ligaments, and heart muscle.

• Proline has a key part in wound healing, molecular recognition, and medical wound dressings that use collagen to promote healing.
• Proline, when combined with vitamin C, promotes healthy connective tissues by repairing cartilage, strengthening joints, tendons, and heart muscle.

Serine (Ser)

Serine, the second amino acid, is likewise an alcohol due to its methyl side chain with a hydroxy group. Serine is essential for lipid and fatty acid metabolism, as well as the synthesis of pyrimidines, purines, creatine, and porphyrins. It is found in all cell membranes, protects nerve fibers with myelin sheaths, and promotes immune system health by producing immunoglobulins and antibodies.

Tyrosine (Tyr)

Tyrosine is a para-hydroxy derivative of the amino acid phenylalanine, which is produced biologically.

• Tyrosine is a precursor to adrenal hormones (epinephrine, norepinephrine, and dopamine) and thyroid hormones (thyroxine). It boosts metabolism and supports the adrenal, thyroid, and pituitary organs.
• Tyrosine can cure chronic fatigue, narcolepsy, anxiety, depression, low sex drive, allergies, and headaches by stimulating metabolism, suppressing appetite, and reducing body fat.

Two New Amino Acids?

Selenocysteine (Sec)

Selenocysteine is the 21st amino acid, however unlike other amino acids in proteins, it is not directly written in the genetic code.

• Selenocysteine is transcribed by a UGA codon, which is typically a stop codon. However, like other amino acids used by cells, selenocysteine requires a specific transfer RNA (tRNA).
• Selenocysteine, the selenium analogue of cysteine, was identified as an amino acid in 2002. It replaces sulfur with a selenium atom.
• Selenocysteine is found in various enzymes, including formate dehydrogenases, glycine reductases, and certain hydrogenases. HIV-1 encodes a functional selenoprotein, and patients with HIV have lower blood plasma selenium levels than the general population.

Pyrrolysine (Pyl)

Pyrrolysine, the 22nd naturally occurring amino acid, is used by some archaea and single-celled bacteria in enzymes involved in methane production. The UAG codon, typically a stop codon, may be changed by a downstream nucleotide to include pyrolysine instead of halting translation, resulting in this lysine derivative.

To summarise, amino acids are the nice units of proteins and every specific particle has its own form and function. Thus, knowledge about the classification of amino acids like essential or non-essential underscores their role in our diet and our body. Consuming different types of amino acids in ones meal promotes one’s health and assists in the development of muscles. Maybe it is time to find out more on how one can optimize the intake of these nutrients in daily diet for better health. Trust me your body will be as happy as you are!