External respiration involves the:

• A. exchange of gases between the lungs and the blood
• B. breakdown of glucose to produce ATP inside the cell
• C. conversion of pyruvate to lactate in the cytoplasm
• D. exchange of gases between the blood and body tissues

Answer: (A)

Verified step by step guidance

1. Understand the term 'external respiration': External respiration refers to the process of gas exchange that occurs between the external environment and the blood in the lungs. This is different from internal respiration, which involves gas exchange between the blood and body tissues.
2. Analyze the options provided: The first option mentions the exchange of gases between the lungs and the blood, which aligns with the definition of external respiration. The other options describe cellular processes or internal respiration, which are unrelated to external respiration.
3. Eliminate incorrect options: The breakdown of glucose to produce ATP inside the cell refers to cellular respiration, not external respiration. Similarly, the conversion of pyruvate to lactate in the cytoplasm is part of anaerobic respiration, and the exchange of gases between the blood and body tissues is internal respiration.
4. Focus on the correct option: The exchange of gases between the lungs and the blood is the correct description of external respiration. This process involves oxygen diffusing from the alveoli into the blood and carbon dioxide diffusing from the blood into the alveoli.
5. Conclude the reasoning: Based on the definition and elimination of incorrect options, the correct answer is the exchange of gases between the lungs and the blood, as this is the primary function of external respiration.