What feature of red blood cells enhances their ability to exchange gases?

The biconcave shape of red blood cells significantly enhances their ability to exchange gases. This unique shape increases the surface area-to-volume ratio, allowing for more efficient diffusion of oxygen and carbon dioxide. The thinness of the red blood cell at the center facilitates gas exchange, as the distance that gases must travel to move in and out of the cell is minimized.

Additionally, the biconcave structure ensures that red blood cells can easily deform as they pass through narrow capillaries, which are essential for reaching tissues where gas exchange occurs. This adaptability further supports their primary function of transporting oxygen from the lungs to body tissues and carrying carbon dioxide back to the lungs for exhalation.

In contrast, a multi-lobed structure is typical of certain white blood cells and does not apply to red blood cells, while the presence of a flexible membrane serves various functions but is not as critical for enhancing gas exchange specifically. Mitochondria are involved in energy production and are not present in mature red blood cells, as they lack organelles to maximize space for hemoglobin, which is the protein responsible for binding and transporting gases.