Glutamine
Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases, and glutamine must be obtained from the diet. It is encoded by the codons CAA and CAG.
Carnitine
Carnitine (β-hydroxy-γ-"N"-trimethylaminobutyric acid, 3-hydroxy-4-"N","N","N"-trimethylaminobutyrate) is a quaternary ammonium compound involved in metabolism in most mammals, plants and some bacteria. Carnitine may exist in two isomers, labeled -carnitine and -carnitine, as they are optically active. At room temperature, pure carnitine is a white powder, and a water-soluble zwitterion with low toxicity. Carnitine only exists in animals as the -enantiomer, and -carnitine is toxic because it inhibits the activity of -carnitine. Carnitine, derived from an amino acid, is found in nearly all organisms and animal tissue. Carnitine is the generic expression for a number of compounds that include L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. It is most accumulated in cardiac and skeletal muscles as it accounts for 0.1% of its dry matter. It was first derived from meat extracts in 1905, therefore the name carnitine is derived from Latin ""carnus"" or flesh. The body synthesizes enough carnitine from lysine side chains to keep up with the needs of energy production in the body as carnitine acts as a transporter of long-chain fatty acids into the mitochondria to be oxidized and produce energy. Some individuals with genetic or medical disorders (like preterm infants) cannot make enough, so this makes carnitine a conditionally essential nutrient for them.