What is the amino acid that all proteins start with?

Answer 1

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent Amino acids are critical to life, and have a variety of roles in metabolism. One particularly important function is as the building blocks of proteins, which are linear chains of amino acids. http://en.wikipedia.org/wiki/Amino_acid === === The answerer to this question did not actually answer it. The question is asking what amino acid do all proteins start with, not for the definition of an amino acid. The answer is methionine, because the gene for every protein has a start codon in the mRNA of AUG, and AUG codes for the amino acid methionine.