Hemoglobin

Every cell needs oxygen to make ATP, but water carries very little oxygen. So blood packs it into hemoglobin. What does hemoglobin carry, and from where to where?

Most machines in the atlas burn ATP or ride an ion flow. Hemoglobin spends no chemical fuel at all. What does the work of loading and unloading oxygen instead?

Hemoglobin has four oxygen seats, one on each heme. It fills up fully in the lungs and empties well in the tissues. How do the four seats work to make this possible?

Myoglobin in muscle has the same fold as one hemoglobin chain, but it is a single chain with a single heme. Why can it not switch as a team like hemoglobin?

Without oxygen, the iron in each heme sits a little out of its flat ring. What happens when the first oxygen binds that iron?

Working muscle makes acid and carbon dioxide. Hemoglobin is like a sponge that squeezes itself in acid. What do acid and carbon dioxide do to hemoglobin there?

A red blood cell is a tiny bag packed with hemoglobin, and your body has about 25 trillion of them. Roughly how many hemoglobin molecules does one red cell hold?

A red blood cell carries about a billion oxygen molecules on each trip. Why does it not burn that oxygen itself?

Fetal hemoglobin grips oxygen more tightly than adult hemoglobin, so a fetus can take oxygen from its mother's blood. How does an approved Cas9 therapy use this to treat sickle cell disease?

The classic picture says hemoglobin has just two shapes, a weak-grip one and a strong-grip one. What does newer work add to that picture?