Final answer:
The essential amino acid among the given options is B. Histidine. Essential amino acids cannot be synthesized by the body and must be consumed through the diet. Histidine is important for proper growth and development.
Step-by-step explanation:
Essential Amino Acids
Amino acids are the building blocks of proteins, and essential amino acids are those that the human body cannot synthesize and must obtain from the diet. Of the options provided in the question: Alanine, Histidine, Proline, and Tyrosine, the essential amino acid is Histidine. This is because our bodies cannot produce histidine, so it must be acquired through food we eat. Amino acids like Alanine, Proline, and Tyrosine are capable of being synthesized by the human body and are therefore classified as non-essential amino acids.
The nine essential amino acids include: valine, isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, histidine, and lysine. It's key to ensure a balanced diet to provide all of these necessary nutrients for the body's function and protein synthesis.