Hemoglobin is a miracle of construction

Hemoglobin sits inside a red blood cell, constituting 96 percent of the cells’ dry weight; its function is to pick up oxygen and transport it through the bloodstream to every cell in the body. Blood gains its red color from the iron in hemoglobin, which turns reddish when it rusts (and for the same reason). When the oxygen atoms reach their destination and are released. The red color fades, which is why blood in your veins is bluish. Venous blood is on the return journey to the lungs, where it will start the process of oxygen transport all over again. The ability of hemoglobin to carry oxygen is seventy times greater than if the oxygen were simply dissolved in the blood. 

As a molecule, hemoglobin is a miracle of construction. The hemoglobin molecule is built from 10,000 atoms, creating a vast space that exist so that exactly four iron atoms can pick up four oxygen atoms for transport.

The task that faced inorganic matter billions of years ago on planet Earth was as follows:

- Oxygen had to be set free into the atmosphere without getting gobbled up by greedy atoms and molecules around it.

- At the same time, some of the oxygen had to be gobbled up to form complex organic chemicals.

- Those organic chemicals had to be structured into proteins, of which hemoglobin is one of the most complex.

- Hemoglobin had to be arranged internally so that it encased four iron atoms, which are absent from hundreds of other proteins, including those that resemble hemoglobin in their working parts.

- The iron atoms couldn’t be inertly encased, like locking diamonds up in a safety deposit box. The iron had to be charged (as a positive ion) so that it could pick up oxygen atoms. But it wasn’t permitted to steal any of the oxygen already being used to build proteins.

Finally, the machinery necessary for constructing all of the above organic chemicals had to remember how to do it the next time and the next and the next, while other nanomachines sitting nearby in the cell had to remember hundreds of different chemical processes without interfering with the machine that makes hemoglobin. Meanwhile, time matters. The nucleus of the cell, DNA has to remember—and put into motion with precise time—the whole enterprise.

Deepak Chopra and Menas C. Kafatos, You are the Universe: Discovering Your Cosmic Self and Why It Matters (Harmony Books, 2017), 218-221.