It is hemoglobin that is the oxygen transport substance in blood. Wikipedia has some good information on this metalloprotein, and a link is provided.
The red blood cell is the iron-containing compound that carries oxygen in the bloodstream. The color of red blood cells will even change due to the concentration of iron in the blood.
I beleive it is hemoglobin considering that is what transfers oxygen in the first place and in the fact that it is a protien.
-ZyraEdits
Iron is present in a compound called hemoglobin, which is present in red blood cells, which carry oxygen in the blood.
Haemoglobin
hemoglobn
hemoglobin
Oxygen enters the body by being absorbed into the blood (specifically, it is absorbed by red blood cells which contain an oxygen-carrying compound known as hemoglobin) when air is inhaled into the lungs, which have a highly porous, spongy structure which facilitates the exposure of blood to the air.
Haemoglobin
then they are red if they are not carrying oxygen then they are a purple red.
a colorless protein obtained by removing heme from hemoglobin; the oxygen carrying compound in red blood cells
Hemoglobin
haemoglobin
Hemoglobin is the oxygen carrying molecule in red blood cells.
White blood cell
Red blood cells
If the blood cell is red you can tell that it has oxygen
Erethrocytes
hemoglobin