Final answer:
The molecular weight of the gas is NOT an important factor in gas exchange; critical factors include partial pressure of the gases, available surface area, and rate of blood flow through tissue.
Step-by-step explanation:
Internal and external respiration depends on several factors for efficient gas exchange. Of the options provided, the one that is NOT an important factor in gas exchange is a. the molecular weight of the gas. Instead, other critical factors include b. partial pressure of the gases, c. available surface area, and d. rate of blood flow through the tissue, because these directly influence how gases like oxygen and carbon dioxide diffuse across the respiratory membranes.
For example, partial pressure differences drive the oxygen to dissociate from hemoglobin and diffuse from areas of high pressure in the blood to areas of low pressure in the tissues needing oxygen. Conversely, carbon dioxide diffuses in the opposite direction, from the tissues back into the blood, because of its higher partial pressure in tissue fluid. A sufficient surface area in the lungs allows for more gas molecules to diffuse simultaneously, and adequate blood flow ensures that gases are delivered and removed from tissues effectively.