Amino acid

In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human muscles and other tissues.

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.

The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids.

Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate.

Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.

Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available from the diet and only require a small number of biosynthetic steps for conversion.

They can be classified according to the core structural functional groups' locations as alpha- , beta- , gamma- or delta- amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.).

Three amino acids (cysteine, cystine, and methionine) and two vitamins (biotin and thiamine) are organosulfur compounds.

These are all L -stereoisomers ("left-handed" isomers), although a few D -amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator ( D -serine), and in some antibiotics.

Serine (symbol Ser or S) is an ɑ-amino acid that is used in the biosynthesis of proteins.

Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.

Some important biological macromolecules include: proteins, which are composed of amino acid monomers joined via peptide bonds, and DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.

In biochemistry, amino acids having both the amine and the carboxylic acid groups attached to the first (alpha-) carbon atom have particular importance.

These can be inorganic, for example water and metal ions, or organic, for example the amino acids, which are used to synthesize proteins.

The other two ("non-standard" or "non-canonical") are selenocysteine (present in many prokaryotes as well as most eukaryotes, but not coded directly by DNA), and pyrrolysine (found only in some archaea and one bacterium).

Pyrrolysine (symbol Pyl or O; encoded by the 'amber' stop codon UAG) is an α-amino acid that is used in the biosynthesis of proteins in some methanogenic archaea and bacteria; it is not present in humans.

Amino acids are organic compounds that contain amine (-NH 2 ) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid.

In proteins, side chains are attached to the alpha carbon atoms of the amino acid backbone.

N-formylmethionine (which is often the initial amino acid of proteins in bacteria, mitochondria, and chloroplasts) is generally considered as a form of methionine rather than as a separate proteinogenic amino acid.

N-Formylmethionine (fMet) is a derivative of the amino acid methionine in which a formyl group has been added to the amino group.

N-formylmethionine (which is often the initial amino acid of proteins in bacteria, mitochondria, and chloroplasts) is generally considered as a form of methionine rather than as a separate proteinogenic amino acid.

Chloroplasts carry out a number of other functions, including fatty acid synthesis, much amino acid synthesis, and the immune response in plants.

Codon–tRNA combinations not found in nature can also be used to "expand" the genetic code and form novel proteins known as alloproteins incorporating non-proteinogenic amino acids.

An expanded genetic code is an artificially modified genetic code in which one or more specific codons have been re-allocated to encode an amino acid that is not among the 20 common naturally-encoded proteinogenic amino acids.

Codon–tRNA combinations not found in nature can also be used to "expand" the genetic code and form novel proteins known as alloproteins incorporating non-proteinogenic amino acids.

A transfer RNA molecule is used in translation and consists of a single RNA strand that is only about 80 nucleotides long, containing an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA and (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA ) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length, that serves as the physical link between the mRNA and the amino acid sequence of proteins.

The other two ("non-standard" or "non-canonical") are selenocysteine (present in many prokaryotes as well as most eukaryotes, but not coded directly by DNA), and pyrrolysine (found only in some archaea and one bacterium).

Under the genetic code, these RNA strands specify the sequence of amino acids within proteins in a process called translation.

Hydroxyproline, a major component of the connective tissue collagen, is synthesised from proline.

Collagen consists of amino acids bound together to form a triple helix of elongated fibril known as a collagen helix.

Glycine is a biosynthetic precursor to porphyrins used in red blood cells.

Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain.

N-formylmethionine (which is often the initial amino acid of proteins in bacteria, mitochondria, and chloroplasts) is generally considered as a form of methionine rather than as a separate proteinogenic amino acid.

Methionine (abbreviated as Met or M; encoded by the codon AUG) is an α-amino acid that is used in the biosynthesis of proteins.

Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food.

An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized de novo (from scratch) by the organism at a rate commensurate with its demand, and thus must be supplied in its diet.

Because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, feed, and food technology.

The class of nutrient compounds includes vitamins, minerals, fiber, fatty acids and amino acids.

Codon–tRNA combinations not found in nature can also be used to "expand" the genetic code and form novel proteins known as alloproteins incorporating non-proteinogenic amino acids.

An alloprotein is a novel synthetic protein containing one or more "non-natural" amino acids.

Pyrrolysine and selenocysteine are encoded via variant codons; for example, selenocysteine is encoded by stop codon and SECIS element.

Proteins are based on polypeptides, which are unique sequences of amino acids.

These are all L -stereoisomers ("left-handed" isomers), although a few D -amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator ( D -serine), and in some antibiotics.

Important examples are keto-enol tautomerism and the equilibrium between neutral and zwitterionic forms of an amino acid.

Hydroxyproline, a major component of the connective tissue collagen, is synthesised from proline.

It contains an α-amino group (which is in the protonated NH 2 + form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO − form under biological conditions), and a side chain pyrrolidine, classifying it as a nonpolar (at physiological pH), aliphatic amino acid.

In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered.

He laid founding work in identifying amino acids, the fundamental building blocks of proteins.

In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered.

Asparagine (symbol Asn or N ), is an α-amino acid that is used in the biosynthesis of proteins.