Selenocysteine is the 21st proteinogenic amino acid. Selenoproteins contain selenocysteine residues. Selenocysteine is an analogue of the more common cysteine with selenium in place of the sulfur.
Selenocysteine synthesis
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metab
Polypeptide
John Kendrew with model of myoglobin in progress
Proteins in various cellular compartments and structures tagged with green fluorescent protein (here, white)
Constituent amino-acids can be analyzed to predict secondary, tertiary and quaternary protein structure, in this case hemoglobin containing heme units.