What protein in red blood cells carries oxygen throughout the body?

Hemoglobin is the protein in red blood cells that is primarily responsible for carrying oxygen throughout the body. It achieves this by binding to oxygen molecules in the lungs, where oxygen concentration is high, and releasing them in tissues where oxygen is needed. The structure of hemoglobin, which consists of four subunits, allows it to bind up to four oxygen molecules efficiently, a process that is crucial for sustaining cellular respiration and energy production.

Myoglobin, while also a protein that binds oxygen, is found in muscle tissue and is responsible for storing oxygen rather than transporting it in the bloodstream. Transferrin is a protein that primarily binds and transports iron in the bloodstream, which is important for red blood cell production but not for oxygen transport itself. Albumin is a protein that helps maintain oncotic pressure in the blood and carries various substances, but it is not involved in oxygen transport. Thus, hemoglobin plays a vital role in oxygen delivery, making it the correct answer in this context.