Hemoglobin made up of globin that has 4 polypeptide chains 2 alpha and 2 beta, all of which are bound to the ring shaped heme Each hemoglobin molecule binds 4 O2 1 for each heme, 280 million hemoglobin molecules in a RBC—over a billion molecules of O2 can be bound by a single RBC Keeping hemoglobin in in erythrocytes rather than in plasma prevents it from breaking up and diffusing out of capillaries and it keeps hemoglobin from having effects on blood viscosity and osmotic pressure. Oxygen bound to hemoglobin forms the complex oxyhemoglobin, changes conformation and is a bright red color. When oxygen is released the hemoglobin becomes deoxyhemoglobin and changes shape again, becoming a darker red. Iron-2 reaction reverses as blood flows through capillaries CO2 binds with AAs in the globin part of hemoglobin—this is carbaminohemoglobin NO also binds to hemoglobin and hemoglobin can release NO to cause vasodilation
