Q1. [3] medium thorough-understanding
Carbon dioxide and oxygen are both transported through the same blood vessels, yet by entirely different mechanisms. (i) Describe how each gas is transported in human blood. (ii) Red blood corpuscles lack a nucleus. How does this structural feature directly aid their primary function in gas transport?
Generated by claude-sonnet-4-6 · 2026-06-26 01:01 · grounding rag
Model Answer
(i) Transport of gases in blood:
- Oxygen is carried by haemoglobin present in red blood corpuscles (RBCs). It combines with haemoglobin to form oxyhaemoglobin.
- Carbon dioxide is transported in dissolved form in the plasma.
(ii) RBCs lack a nucleus, so the entire cell space is available to pack more haemoglobin molecules. This increases the oxygen-carrying capacity of each RBC, directly aiding efficient gas transport.
Source: Chapter 5, Section 5.4.1 Transportation in Human Beings
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Explanation
- The textbook explicitly states: "Oxygen is carried by the red blood corpuscles" (via haemoglobin) and "Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form." Use these exact mechanisms.
- For part (ii), the examiner wants you to link the structural feature (no nucleus → more space) to the functional benefit (more haemoglobin → more O₂ carried). This is a classic structure-function question — one crisp logical sentence scores full marks.
- Do not confuse the two gases: O₂ → RBCs/haemoglobin; CO₂ → plasma (dissolved).