Which statement correctly describes the partial pressures of oxygen and carbon dioxide in systemic cells under resting conditions?

• A. Systemic cells have equal partial pressures of oxygen (O_2) and carbon dioxide (CO_2) as arterial blood.
• B. Systemic cells have a higher partial pressure of oxygen (O_2) and a lower partial pressure of carbon dioxide (CO_2) compared to arterial blood.
• C. Systemic cells have a lower partial pressure of oxygen (O_2) and a higher partial pressure of carbon dioxide (CO_2) compared to arterial blood.
• D. Systemic cells have no partial pressure of oxygen (O_2) under resting conditions.

Answer: (C)

Verified step by step guidance

1. Understand that partial pressure refers to the pressure exerted by a single gas in a mixture of gases, which in the context of systemic cells relates to the concentration of oxygen (O_2) and carbon dioxide (CO_2) available or produced in those cells.
2. Recall that arterial blood carries oxygen-rich blood from the lungs to the systemic cells, so the partial pressure of oxygen (O_2) in arterial blood is relatively high, while the partial pressure of carbon dioxide (CO_2) is relatively low.
3. Recognize that systemic cells consume oxygen for cellular respiration, which lowers the partial pressure of oxygen inside the cells compared to arterial blood.
4. Understand that as a result of cellular respiration, systemic cells produce carbon dioxide as a waste product, increasing the partial pressure of CO_2 inside the cells compared to arterial blood.
5. Conclude that under resting conditions, systemic cells have a lower partial pressure of oxygen (O_2) and a higher partial pressure of carbon dioxide (CO_2) compared to arterial blood, reflecting the exchange of gases during metabolism.