Final answer:
The A-C membrane, or respiratory membrane, is significant in the respiratory system because it allows gas exchange between the alveolar and capillary walls.
Step-by-step explanation:
The A-C membrane, also known as the respiratory membrane, is a significant structure in the respiratory system because it allows gas exchange. This membrane is formed by the alveolar and capillary walls, where oxygen enters the bloodstream and carbon dioxide exits. Through this process, oxygen is delivered to body tissues and carbon dioxide is removed as a waste product of cellular respiration.