Biology Respiration / Gaseous Exchange MDCAT 2017
PMDC Verified Question 29 of 34
Gaseous exchange in animals takes place with the help of process called as:
A
Active transport
B
Cyclosis
C
Diffusion
D
Phagocytosis
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Diffusion
Concept: The movement of gases across biological membranes is solely governed by kinetic energy and concentration gradients.

Solution:
  • Gaseous exchange does not require ATP or carrier proteins.
  • Oxygen and carbon dioxide are small, uncharged molecules that pass freely through the phospholipid bilayers of alveoli and capillaries.
  • They move exclusively via simple diffusion, traveling strictly from areas of higher partial pressure to areas of lower partial pressure.


Why other options are incorrect:
  • Active transport: Requires ATP and pushes molecules against gradients; gases never utilize this.
  • Cyclosis: Cytoplasmic streaming inside cells.
  • Phagocytosis: Cellular eating (engulfing large particles).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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