Final answer:
A red blood cell contains approximately 250 million hemoglobin molecules, which allows it to transport roughly one billion oxygen molecules due to the erythrocytes' efficient design.
Step-by-step explanation:
Approximately 250 million hemoglobin molecules are in a single red blood cell. Hemoglobin is the iron-containing protein that is responsible for transporting oxygen and giving red blood cells their characteristic red color. With each hemoglobin molecule having the capacity to bind four oxygen molecules, a single erythrocyte (red blood cell) can carry roughly one billion molecules of oxygen.
In addition to oxygen transport, hemoglobin also carries carbon dioxide. The absence of organelles in erythrocytes, which is a characteristic of mammalian red blood cells, provides more space for hemoglobin molecules and prevents the use of oxygen for metabolic respiration within the cells. This design enhances the efficiency of oxygen transport in the blood.