Basic amino acid is?

Appeared in: NHM UP Staff Nurse - 2017

Explanation

Arginine is classified as a basic amino acid.
Its side chain contains a guanidinium group, which is protonated and carries a positive charge at physiological pH (around 7.4).
This positive charge on the R-group is the defining feature of a basic amino acid.

Option A: Asparagine has a polar, uncharged side chain containing an amide group. This makes it a neutral amino acid, not a basic one.
Option C: Similar to asparagine, glutamine possesses a polar but uncharged amide group in its side chain, which classifies it as a neutral amino acid.
Option D: This option is incorrect because only Arginine is a basic amino acid among the choices. Asparagine and Glutamine are neutral.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of amino acids based on the chemical properties of their side chains as background academic context rather than a clinical decision trigger.
Arginine is the precursor for nitric oxide (NO), a crucial signaling molecule that acts as a vasodilator, helping to regulate blood pressure and improve blood flow.
It plays a vital role in the urea cycle, the body's primary pathway for detoxifying and excreting ammonia, a toxic byproduct of protein metabolism. A defect in this cycle can lead to hyperammonemia.
What if? If a patient has a condition requiring rapid tissue growth (e.g., after surgery) or is under severe metabolic stress (like sepsis), Arginine can become 'conditionally essential.' This means the body's synthesis can't keep up with demand, and it must be supplied through the diet or supplementation to prevent deficiency.

How to Approach the Question

First, identify the core of the question, which is to classify an amino acid as 'basic'. This is a factual recall question from biochemistry.
Recall the classification of the 20 standard amino acids based on the chemical properties of their side chains (R-groups).
Remember that basic amino acids have side chains that are positively charged at physiological pH. The three main basic amino acids are Arginine, Lysine, and Histidine.
Evaluate each option against this knowledge: Asparagine and Glutamine have neutral amide groups. Arginine has a basic guanidinium group.
Based on this classification, confidently select Arginine as the correct answer and eliminate the other options.

Concept Tested & Keywords

Concept Tested: Classification of amino acids based on the chemical properties of their side chains.
Stem keywords: Basic amino acid
Lead-in keywords: is

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 96-98

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

Practise the full NHM UP Staff Nurse - 2017

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