Choose the word which is least like the others in the group:

Appeared in: RML MAINS 2025

Explanation

Hemoglobin is the correct choice as it is functionally and structurally different from the other options.
It is a respiratory pigment and a transport protein found inside red blood cells, with its primary role being oxygen transport.
Insulin, Adrenaline, and Thyroxine are all classified as hormones.
Hormones are chemical messengers secreted by endocrine glands directly into the bloodstream to regulate the activity of target cells and organs.

Option A: Insulin is a hormone, similar to Adrenaline and Thyroxine. It is secreted by the beta cells of the pancreas and is essential for regulating blood glucose levels.
Option B: Adrenaline (also known as epinephrine) is a hormone and neurotransmitter. It belongs to the same general class (hormones) as Insulin and Thyroxine.
Option D: Thyroxine is a hormone produced by the thyroid gland, placing it in the same category as Insulin and Adrenaline. It plays a crucial role in regulating metabolism.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of biological molecules as background academic context rather than a clinical decision trigger.
Understanding the difference between hormones and other proteins is fundamental in physiology and pharmacology. Misclassifying these can lead to critical errors in understanding disease processes and treatments.
Nurses administer hormones (like Insulin) and monitor their effects, as well as assess conditions related to transport proteins (like anemia, which involves hemoglobin).
What if? If the option 'Hemoglobin' were replaced with 'Glucagon', the question becomes more nuanced. All four would be hormones. The odd one out might then be Adrenaline, as it's an amine derivative, while Insulin and Glucagon are peptide hormones, and Thyroxine is an iodinated amino acid derivative. The classification would shift from function to chemical structure.

How to Approach the Question

First, identify the core nature or function of each word in the list.
Insulin is a hormone that regulates blood sugar.
Adrenaline is a hormone related to the stress response.
Hemoglobin is a protein that carries oxygen in the blood.
Thyroxine is a hormone that regulates metabolism.
Notice that three of the options (Insulin, Adrenaline, Thyroxine) share a common classification: they are all hormones.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2B p. 97-99

E6 Physiology Guyton 4SAE Part 3 p. 5-7

E6 Physiology Essentials Sembulingam 10e Part 2 p. 62-64

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