Which statement correctly describes the two types of respiration?

Which statement correctly describes the two types of respiration?

• A. Internal respiration: exchange of gas between blood and tissue cells; External respiration: exchange of gas between lung air and blood
• B. Internal respiration: exchange of gas between lung air and blood; External respiration: exchange of gas between blood and tissue cells
• C. Internal respiration: gas exchange in lungs; External respiration: gas exchange in tissues
• D. Internal respiration: exchange of carbon dioxide; External respiration: exchange of oxygen

Answer: (A)

The main idea is that respiration has two gas-exchange stages at different sites. External respiration happens at the lungs, where oxygen moves from the air in the alveoli into the blood and carbon dioxide moves from the blood into the alveolar air to be exhaled. Internal respiration happens at the tissues throughout the body, where oxygen moves from the blood into tissue cells to support metabolism and carbon dioxide moves from the cells into the blood to be carried back to the lungs. The described statement correctly assigns internal respiration to the exchange between blood and tissue cells and external respiration to the exchange between lung air and blood. This aligns with how oxygen is delivered to tissues and how carbon dioxide is removed from the body.

The main idea is that respiration has two gas-exchange stages at different sites. External respiration happens at the lungs, where oxygen moves from the air in the alveoli into the blood and carbon dioxide moves from the blood into the alveolar air to be exhaled. Internal respiration happens at the tissues throughout the body, where oxygen moves from the blood into tissue cells to support metabolism and carbon dioxide moves from the cells into the blood to be carried back to the lungs.

The described statement correctly assigns internal respiration to the exchange between blood and tissue cells and external respiration to the exchange between lung air and blood. This aligns with how oxygen is delivered to tissues and how carbon dioxide is removed from the body.