A Level Biology Practice Exam

What does expiratory reserve volume refer to?

1. The total volume of air in the lungs

2. The amount of air exchanged during normal breathing

3. The extra air that can be forced out after normal exhalation

4. The reserve of oxygen available in cells

The correct answer is: The extra air that can be forced out after normal exhalation

Expiratory reserve volume specifically refers to the additional amount of air that can be forcibly exhaled from the lungs after the expiration of a normal tidal volume breath. This volume represents the capacity of the lungs to expel more air than what's achieved during regular breathing, which is significant for understanding lung function and respiratory health. In contrast, the total volume of air in the lungs is known as total lung capacity and includes all of the lung volumes. The amount of air exchanged during normal breathing is referred to as tidal volume, which is much smaller than the expiratory reserve volume. The reserve of oxygen available in cells pertains to cellular respiration and oxygen utilization, rather than directly related to lung capacity.