What substance is responsible for carrying oxygen and carbon dioxide in the blood?

Hemoglobin is the protein in red blood cells that is primarily responsible for the transport of oxygen and carbon dioxide in the bloodstream. It binds to oxygen in the lungs and releases it in the tissues where it is needed for cellular respiration. Simultaneously, hemoglobin picks up carbon dioxide — a waste product of metabolism — from the tissues and transports it back to the lungs for exhalation. This dual role makes hemoglobin essential for maintaining the body’s oxygen levels and regulating carbon dioxide levels, critical processes for sustaining life.

Other components in the blood serve different functions. Plasma, for instance, is the liquid portion of blood that carries various substances, including nutrients, hormones, and waste products, but does not specifically carry oxygen or carbon dioxide. Platelets are primarily involved in blood clotting, and white blood cells play a key role in the immune response, protecting the body against infection.