Calculate the magnification of the image. (b) Briefly describe how gaseous exchange occurs between the alveoli and capillaries. (c) Briefly explain how oxygen is transported from the alveoli to the bo

The length of the scale bar in the figure is approximately $2.0 \text{ cm} = 20 \text{ mm}$.

The scale bar represents an actual size of $10 \mu \text{m}$.

Magnification = Image size / Actual size.

The magnification is $\boxed{2000}$.

24. (b)
Gaseous exchange occurs by diffusion across the thin walls of the alveolus and the capillary. Oxygen, which is at a higher partial pressure in the alveolar air space, diffuses across the alveolar and capillary walls into the blood. Simultaneously, carbon dioxide, which is at a higher partial pressure in the capillary blood, diffuses from the blood into the alveolar air space to be exhaled.

24. (c)
Oxygen diffuses from the alveoli into the blood capillaries. Inside the red blood cells, oxygen binds with hemoglobin to form oxyhemoglobin. This oxygenated blood is then pumped by the heart to the body tissues. At the tissues, where oxygen concentration is lower, oxyhemoglobin dissociates, releasing oxygen. The oxygen then diffuses from the red blood cells, through the plasma, and into the tissue cells for cellular respiration.