What is the primary role of hemoglobin in the body?

Hemoglobin's primary role in the body is to transport oxygen from the lungs to the tissues and organs. It is a protein found in red blood cells that binds to oxygen molecules, allowing for efficient delivery throughout the circulatory system. This process is essential for cellular respiration, where oxygen is used to produce energy in the form of adenosine triphosphate (ATP), which is vital for the function and survival of cells.

The other options do not accurately reflect hemoglobin's main function. While nutrients are transported in the bloodstream, this is primarily the role of plasma proteins, not hemoglobin. Similarly, fighting infections is primarily the responsibility of the immune system, particularly white blood cells, rather than hemoglobin. Clotting blood involves proteins in the plasma known as clotting factors, which work together to stop bleeding, whereas hemoglobin specifically focuses on oxygen transport.