The maximum amount of carbon dioxide in the human body is transported as:

UPUMS Nsg.Officer-2024

Applied Physiology

Easy

Appeared in: UPUMS Nsg.Officer-2024

Explanation

The vast majority of carbon dioxide, approximately 70-75%, is transported in the blood in the form of bicarbonate ions (HCO₃⁻).
Inside red blood cells, the enzyme carbonic anhydrase rapidly catalyzes the conversion of CO₂ and water into carbonic acid (H₂CO₃).
This carbonic acid then quickly dissociates into hydrogen ions (H⁺), which are buffered by hemoglobin, and bicarbonate ions (HCO₃⁻).
The bicarbonate ions are then transported out of the red blood cell into the plasma for transport to the lungs, in a process called the chloride shift.

Option B: This option is incorrect because the correct answer, 'Bicarbonate', is listed as one of the choices.
Option C: Carbide is a chemical compound containing carbon and a less electronegative element, typically a metal. It has no physiological role in gas transport in the human body.
Option D: Amylase is a digestive enzyme primarily responsible for breaking down carbohydrates (starches) into simpler sugars. It is not involved in the transport of respiratory gases like carbon dioxide.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanisms of Carbon Dioxide Transport in Blood as background academic context rather than a clinical decision trigger.
The bicarbonate buffer system is the most important buffer system in the blood, crucial for maintaining blood pH within the narrow normal range of 7.35-7.45. Imbalances in CO₂ transport can lead to respiratory acidosis (too much CO₂) or alkalosis (too little CO₂).
Nurses monitor respiratory rate, depth, and blood gas values (like PaCO₂ and HCO₃⁻) to assess a patient's ventilation and acid-base status.
What if? - If a patient is administered a carbonic anhydrase inhibitor (e.g., acetazolamide), the formation of bicarbonate would be significantly reduced. This would impair CO₂ transport, leading to a rise in tissue and blood CO₂ levels (hypercapnia) and causing respiratory acidosis.

How to Approach the Question

First, identify that the question is asking for the primary or main method of carbon dioxide transport in the body.
Recall the three physiological mechanisms for CO₂ transport in the blood: dissolved in plasma, bound to hemoglobin (as carbaminohemoglobin), and as bicarbonate ions.
Compare the relative contribution of each method. Remember that transport as bicarbonate ions accounts for the vast majority (around 70%).
Evaluate the given options. 'Bicarbonate' directly matches the primary transport mechanism. 'Carbide' and 'Amylase' are physiologically irrelevant to gas transport.
Conclude that 'Bicarbonate' is the correct answer as it represents the transport method for the maximum amount of CO₂.

Concept Tested & Keywords

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 14-16

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