If you couldn't remember which were essential; then alternative would have been to realize that growing children need cells to divide. This requires DNA replication and translation. Of which the nucleic acid thyime is important. It requires a methyl transfer.

This is where methionine comes in. Methionine combines with ATP to form SAM (a methyl donor)

Yo dawg we all about PVT TIM HaLL

Phenylalanine, Valine, TryptoDANK, Threonine, Isoleucine, Methionine, Histidine, Leucine Lysine

1. "Three HAL fans will try meth"
    a. Threonine = Three 
    b. Histidine; Arginine; Lysine = HAL
    c. Phenylalanine = fans
    d. Valine; Isoleucine; Leucine = will
    e. Tryptophan = try
    f. Methionine = meth

essential Amino acids (AA)

1) Adults require 9 (AA) = able to make argnine via urea cycle 2) Children require 10 (AA) = they are still developing 3) With PKU tyrosine becomes essential in both adults and children

Let's say you didn't know methionine was essential.

(A) Alanine -- you can create alanine from the enzyme ALT (alanine aminotransferase), thus this enzyme cannot be essential

(B) Aspartate -- you can create aspartate from the enzyme AST (aspartate aminotransferase), thus this enzyme cannot be essential

(C) Glycine -- this one is low yield, but it is made from serine (serine + THF -> CO2 + Me-THF + glycine). If you didn't know about this, you had a 50/50 shot

(E) Tyrosine -- you can create tyrosine from phenylalanine (unless of course you have phenylketonuria), and thus this cannot be essential.

For anyone confused trying to follow @usmleuser007's comment

Slightly modified

Essential amino acids mnemonic "Ah, Three fans will try meth"the

Ah = arginine, histidine

Three = Threonine

Fans (phans)= Phenylalanine

Vill (will -- German accent pronouncing English word "will") = valine, isoleucine, leucine, lysine

Try = tryptophan

Meth = Methionine

The way I remember the essential amino acids is by referencing the amino acids groups I already know. So the essential amino acids are:

1. The branched chain amino acids: Isoleucine, Leucine, and Valine

2. The ringed amino acids EXCEPT Tyrosine (which becomes essential in those with PKU): Tryptophan, Histidine, Phenylalanine

3. The sulfur containing amino acids: Cysteine and Histidine (You will see debate over whether Cysteine qualifies as essential or not)

4. The two you just have to memorize: Threonine and Lysine

a little misleading her increase in weight made it seem as if she had low thyroid hormone and tyrosine is a precursor.

B12 comes from protein and is a necessary cofactor for methionine synthase. Low B12 = low methionine.

Methionine is an essential amino acid. All others listed are not.