Why red blood cell must be flexible?

Red blood cells (RBCs) must be flexible to navigate through the narrow and winding capillaries in the circulatory system. Their unique biconcave shape allows them to deform easily, which is essential for squeezing through tight spaces and maximizing surface area for oxygen and carbon dioxide exchange. This flexibility also helps prevent rupture as they traverse various blood vessels under different pressures. Overall, flexibility is crucial for efficient blood flow and respiratory function.