Identify an essential amino acid from the following?

Appeared in: DSSSB - 28 August 2019 (Shift-1)

Explanation

Valine is one of the nine essential amino acids required by the human body.
Essential amino acids cannot be synthesized by the body in sufficient amounts and therefore must be supplied through the diet.
Valine is a branched-chain amino acid (BCAA) that is critical for muscle growth, tissue repair, and energy production.

Option A: Glycine is a non-essential amino acid, meaning the body can synthesize it, primarily from serine.
Option B: Serine is a non-essential amino acid that the body produces from other molecules, including the glycolytic intermediate 3-phosphoglycerate.
Option D: Proline is a non-essential amino acid that the body can synthesize from the amino acid glutamate.

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 use knowledge of essential amino acids to assess nutritional status and provide dietary counseling, especially for vulnerable populations like postsurgical patients, burn victims, or those with malnutrition, who have increased protein requirements for healing.
Understanding this concept is vital in managing patients with metabolic disorders like Phenylketonuria (PKU), where the intake of the essential amino acid phenylalanine must be strictly limited.
What if the patient is a vegan? A nurse would need to advise the patient on combining different plant-based protein sources (like beans and rice) to ensure they receive a complete profile of all essential amino acids, as most plant proteins are incomplete on their own.

How to Approach the Question

First, understand the question is asking to identify an 'essential' amino acid from the list.
Recall the definition of an essential amino acid: one that the body cannot produce and must be obtained from the diet.
Mentally review the list of the nine essential amino acids. A common mnemonic is 'PVT TIM HALL' (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine - conditionally, Leucine, Lysine).
Scan the options: Glycine, Serine, Valine, Proline.
Identify 'Valine' as a component of the essential amino acid list.
Confirm that Glycine, Serine, and Proline are classified as non-essential or conditionally essential, as the body can synthesize them.

Concept Tested & Keywords

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

E6 Medicine Davidson Principles Practice 24e p. 717-719

E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 260-262

Practise the full DSSSB - 28 August 2019 (Shift-1)

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