Which of the following amino acids is considered essential in humans?

• A. Glycine
• B. Leucine
• C. Tyrosine
• D. Glutamine

Answer: (B)

Verified step by step guidance

1. Understand the concept of essential amino acids: Essential amino acids are those that cannot be synthesized by the human body and must be obtained through the diet. Non-essential amino acids, on the other hand, can be synthesized by the body.
2. Review the list of essential amino acids in humans: The essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
3. Analyze the options provided: Glycine, Tyrosine, and Glutamine are non-essential amino acids because the human body can synthesize them. Leucine, however, is an essential amino acid and must be obtained through dietary sources.
4. Confirm the classification of Leucine: Leucine is one of the branched-chain amino acids (BCAAs) and plays a critical role in protein synthesis and metabolic functions, making it essential for humans.
5. Conclude that Leucine is the correct answer: Based on the definition and classification of essential amino acids, Leucine is the amino acid from the given options that is considered essential in humans.