1. Hemoglobin/Hb/Hgb is the iron-containing oxygen-transport metalloprotein which is present
in red blood cells (erythrocytes) of almost all vertebrates (the exception being the fish
family  Channichthyidae ) as well as the tissues of some invertebrates
2. Hemoglobin carries oxygen in blood from respiratory organs (e.g. lungs or gills) to rest of the
body(i.e. tissue).
3. Metablolism is the energy to power functions of an organism. Hemoglobin releases the oxygen
to permit aerobic respiration .
4. Healthy human have 12 to 25 grams of hemoglobin in every 100 mL of blood.