Which one of the following is an essential amino acid?

Appeared in: BHU NO - 2015

Explanation

Essential amino acids are those that the body cannot produce and must be obtained through diet.
Tryptophan is one of the nine essential amino acids required for various bodily functions, including protein synthesis and as a precursor for serotonin and niacin.
Dietary sources rich in tryptophan include poultry, eggs, cheese, fish, and nuts.

Option A: Alanine is a non-essential amino acid, meaning the body can synthesize it on its own, primarily from pyruvate.
Option B: Serine is a non-essential amino acid. The body can produce it from other metabolites, including the glycolytic intermediate 3-phosphoglycerate.
Option D: Glutamic acid (or glutamate) is a non-essential amino acid that plays a key role as an excitatory neurotransmitter and can be readily synthesized by the body.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of Amino Acids (Essential vs. Non-essential) as background academic context rather than a clinical decision trigger.
Nurses must conduct thorough nutritional assessments, especially for at-risk patients (e.g., post-operative, malnourished, elderly), to ensure adequate intake of essential amino acids for proper healing and recovery.
A deficiency of even one essential amino acid can halt protein synthesis, leading to a negative nitrogen balance, muscle wasting (cachexia), and impaired immune function.
Patient education on dietary sources of complete proteins (containing all essential amino acids), such as meat, dairy, eggs, and soy, is a key nursing intervention.

How to Approach the Question

First, understand the question's core concept: identifying an 'essential amino acid'.
Define 'essential amino acid': an amino acid that the body cannot synthesize and must be obtained from the diet.
Recall or look up the list of the nine essential amino acids: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine. A common mnemonic is 'PVT TIM HaLL'.
Systematically check each option against this list.
Alanine is not on the list (it's non-essential).
Serine is not on the list (it's non-essential).

Concept Tested & Keywords

QJ9QBHJFNv91ZGfDLxIgb3

E6 Pharmacology Nursing Lilley 11e Part 3 p. 231-233

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 291-293

E6 Physiology Ganong 27e Vol 1 Part 1 p. 26-28

Practise the full BHU NO - 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.