 Okay everybody, Dr. O, in this video we're going to talk about hemoglobin in all of its forms. So here you can see hemoglobin. About 95% of the protein in a red blood cell is hemoglobin. So hemoglobin is a combination of proteins and irons. So you've got the protein itself is going to be these four globin molecules. So it's four separate protein subunits put together. Then we have heme. Heme is going to be the red pigment that actually carries the iron. So it's a combination of proteins and then that heme which carries iron. So each of these heme units can carry one iron, which means that every hemoglobin can carry up to four atoms of iron at a time. Now that's a pretty impressive, but there are about 300 million of these hemoglobin molecules in a single red blood cell, which means that each of your 23 trillion red blood cells can carry up to 1.2 billion molecules of oxygen. I've never actually done the math to figure out 23 trillion times 1.2 billion, but it's huge, right? The next, the most important thing here is the different names for hemoglobin. Just so you're not confused, we're going to use words like oxy hemoglobin, deoxy hemoglobin and carbamino hemoglobin, one of the most fun ones to say. But it's all the same hemoglobin. It's just what is it doing with oxygen or carbon dioxide at the time? So once hemoglobin has picked up oxygen at your lungs, it is now called oxy hemoglobin. It's going to be bright red, the bright red blood you think of. Once this hemoglobin gives up its oxygen out to your body tissues, it's going to become darker red and it's now called deoxy hemoglobin. So most of your hemoglobin becomes deoxy hemoglobin as it drops off its oxygen payload. But some, about 23% of the carbon dioxide produced at your tissues is actually going to be carried back to your lungs on hemoglobin. So a hemoglobin that has picked up carbon dioxide is now called carbamino hemoglobin. So oxy hemoglobin is hemoglobin carrying oxygen, deoxy hemoglobin is hemoglobin that's not carrying oxygen, and carbamino hemoglobin is hemoglobin that's carrying carbon dioxide back to the lungs where it can, we can get rid of the CO2, pick up oxygen and do it once again. We'll cover that more in the respiratory system. Okay, I hope this helped. Have a wonderful day. Be blessed.