What is the primary function of red blood cells?

The primary function of red blood cells is to carry oxygen from the lungs to the tissues and organs of the body. They contain a protein called hemoglobin, which binds to oxygen molecules, enabling efficient transport throughout the circulatory system. Once oxygen is delivered to the cells, red blood cells also help transport carbon dioxide, a waste product of metabolism, back to the lungs for exhalation. This crucial role is essential for maintaining the overall metabolic processes and ensuring that body tissues receive the oxygen they require for energy production.

The other options represent different functions that are not associated with red blood cells. For instance, destroying pathogens is primarily the role of white blood cells, which are part of the immune system. Producing insulin is a function of pancreatic cells, specifically beta cells, which play a crucial role in regulating blood glucose levels. Initiating blood clotting is the primary function of platelets, which help prevent excessive bleeding following an injury by aggregating at the site and forming a clot. Thus, the emphasis on the oxygen transportation role of red blood cells highlights their importance in sustaining life and facilitating cellular respiration.