What percentage of oxygen do we exhale?

When we exhale, the air we breathe out contains a significantly lower percentage of oxygen than the air we inhale. The atmosphere contains about 21% oxygen, which is what we take in with each breath. During the process of cellular respiration, our bodies utilize this oxygen to produce energy, thus reducing the oxygen content in the air we subsequently exhale.

In the air we exhale, the oxygen percentage typically drops to around 16%. This indicates that our bodies are effectively using the oxygen, leading to the lower concentration in exhaled air. Consequently, recognizing that 16% reflects the actual oxygen content we provide in our breath is crucial for understanding the respiratory cycle and its efficiency.

The other options do not accurately represent the oxygen content in exhaled air: 5% and 10% are significantly lower than expected, indicating an incomplete understanding of respiratory processes, while 21% corresponds to the oxygen concentration in inhaled air rather than exhaled air.