Here's how it works:

1. Lungs: Oxygen from the air we breathe enters our lungs and passes into tiny blood vessels called capillaries.

2. Hemoglobin: Red blood cells contain a protein called hemoglobin, which has a strong affinity for oxygen. Oxygen molecules bind to hemoglobin in the lungs.

3. Circulation: The oxygen-rich blood is pumped by the heart through the circulatory system to all the body's tissues and organs.

4. Delivery: When the blood reaches the cells, the oxygen detaches from hemoglobin and diffuses into the cells, where it's used for cellular respiration.

5. Carbon Dioxide Transport: The same red blood cells also carry carbon dioxide, a waste product of cellular respiration, back to the lungs to be exhaled.

So, without red blood cells and their special hemoglobin, our bodies wouldn't be able to get the oxygen they need to function!