Which of the following is essential amino acid?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2024

Explanation

Tryptophan is classified as an essential amino acid, which means the human body cannot produce it in sufficient quantities to meet its needs.
It must be obtained from dietary sources such as poultry, eggs, dairy products, nuts, and seeds.
Tryptophan serves as a crucial precursor for the synthesis of vital compounds, including the neurotransmitter serotonin (which regulates mood and sleep) and the vitamin niacin (B3).

Option A: Arginine is a semi-essential (or conditionally essential) amino acid, not a strictly essential one for all individuals.
Option B: Serine is a non-essential amino acid because the body can synthesize it from other metabolites, primarily from the amino acid glycine.
Option D: Glutamic acid is a non-essential amino acid that the body can readily produce. It also functions as a key excitatory neurotransmitter.

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 understand the dietary needs of patients, especially those with malnutrition, metabolic disorders, or receiving Total Parenteral Nutrition (TPN), to ensure they receive a complete profile of essential amino acids.
A deficiency in an essential amino acid like tryptophan can lead to poor nitrogen balance, weight loss, and impaired synthesis of proteins and neurotransmitters, potentially affecting a patient's mood, sleep, and overall recovery.
What if? If the patient were a premature infant, Arginine would be considered fully essential, not semi-essential, because their metabolic pathways are too immature to synthesize it in adequate amounts. This highlights how nutritional requirements are highly dependent on age and clinical condition.

How to Approach the Question

First, identify the core concept of the question, which is 'essential amino acid'.
Recall the definition of an essential amino acid: one that cannot be synthesized by the body and must be obtained through the diet.
Systematically evaluate each option against this definition.
If available, use a mnemonic like 'PVT TIM HALL' (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine, Leucine, Lysine) to recall the list of essential and semi-essential amino acids.
Select the option that fits the definition and is part of the essential list, noting that Arginine and Histidine are often considered semi-essential.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) p. 37-39

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

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

Practise the full RUHS, Jaipur, PB B.Sc Nursing Entrance-2024

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