The 20 Essential Amino Acids

Flashcards summarizing the 20 essential amino acids, categorized by their properties and key features for easier memorization and understanding.

Glycine (Gly / G)

The smallest and only achiral amino acid with a non-polar side chain consisting of a single Hydrogen (-H).

Alanine (Ala / A)

A non-polar amino acid with a methyl group (-CH3) side chain. Very common in proteins.

Valine (Val / V)

An essential non-polar branched-chain amino acid (Isopropyl).

Leucine (Leu / L)

A non-polar branched-chain amino acid (Isobutyl) with a high tendency to form alpha-helices.

Isoleucine (Ile / I)

A non-polar branched-chain amino acid (sec-butyl) and isomer of Leucine.

Methionine (Met / M)

A non-polar, sulfur-containing amino acid coded by the start codon (AUG).

Proline (Pro / P)

A non-polar cyclic imino acid that induces 'kinks' or bends in protein structures.

Phenylalanine (Phe / F)

A non-polar aromatic amino acid with a bulky benzene ring.

Tryptophan (Trp / W)

A non-polar aromatic amino acid with the largest side chain (Indole ring) that absorbs at 280 nm.

Serine (Ser / S)

A polar amino acid with a hydroxyl group (-OH), a key site for phosphorylation.

Threonine (Thr / T)

A polar amino acid with a hydroxyl group, another common site for phosphorylation.

Cysteine (Cys / C)

A polar amino acid with a thiol group (-SH) critical for forming disulfide bridges.

Tyrosine (Tyr / Y)

A polar aromatic amino acid with a phenol group, a precursor for neurotransmitters.

Asparagine (Asn / N)

A polar amide of Aspartate found in glycoproteins (N-linked).

Glutamine (Gln / Q)

A polar amide of Glutamate and nitrogen transporter in the blood.

Aspartic Acid (Asp / D)

A negatively charged (acidic) amino acid with a carboxyl group (-CH2COO-), very hydrophilic.

Glutamic Acid (Glu / E)

A negatively charged (acidic) amino acid with a carboxyl group (-CH2CH2COO-), a key neurotransmitter.

Lysine (Lys / K)

A positively charged (basic) amino acid with a long aliphatic chain ending in an amino group (-NH3+).

Arginine (Arg / R)

A positively charged (basic) amino acid that contains a guanidinium group and is highly basic.

Histidine (His / H)

A positively charged (basic) amino acid with an imidazole ring and a pKa near physiological pH (~6.0).