In a hemoglobin molecule, what element is central to all the structures

Iron. It is at the center of the structure. And because they'll delete my answer if I don't add on: Hemoglobin is the oxygen binding protein of red blood cells and is a globular protein with quaternary structure. Hemoglobin consists of four polypeptide subunits; 2 alpha chains and two beta chains. Hemoglobin transports oxygen in the blood from the lungs to the rest of the body.

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.

put the answers   and i could answer.