The job of hemoglobin is to

Hemoglobin is for transferring oxygen in your blood from the lungs to the tissues.

Hemoglobin is a protein with a quaternary structure, consisting of four subunits.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.