What is the first amino acid in the synthesis of plasma proteins?

The first amino acid in the synthesis of plasma proteins is methionine. This is because methionine is the starting amino acid for the majority of protein synthesizing pathways in eukaryotic cells. During translation, the ribosome recognizes the start codon (AUG) on mRNA, which codes for methionine. As protein synthesis begins, methionine is incorporated into the nascent polypeptide chain.

Methionine also plays a significant role in initiating the protein synthesis process, as it is included as the first amino acid in most newly synthesized proteins. In the context of plasma proteins, which are critical components in various physiological functions, starting the chain with methionine is essential for ensuring proper structure and function of these proteins once they are fully synthesized and folded.

The other amino acids mentioned, while important in various metabolic and physiological processes, do not play this primary role as the initiating amino acid in protein synthesis.