Myoglobin; The Mighty Molecule
Myoglobin is an iron- and oxygen-binding protein that is found in the muscle tissue of vertebrates. Every mammal has this protein in their body. It is closely related to hemoglobin, which is the iron- and oxygen-binding protein in blood.
Essentially, when there is a lot of oxygen in the blood or muscles, like when the animals takes a deep breath, myoglobin binds to oxygen exceptionally well. As the oxygen levels in the body begin to decrease, such as when the animal stays under water longer, myoglobin gradually decreases its ability to hold onto the oxygen. Thus, marine animals are able to maximize how much oxygen they can store from a single breath. (5) Due to having a higher concentration of myoglobin in their muscles, they are able to store more O2 in their body for a longer amount of time than land mammals. A study published in 2013 suggests that the ability of marine mammals to hold their breath for so long may be due, in part, to high levels of myoglobin in their muscles (5). What makes this molecule so useful to marine mammals, is it's altered affinity for oxygen, based on the pH of its environment. |
Research done by Scott Mirceta at the University of Liverpool, England indicates that the concentration of Myoglobin in diving mammals is about thirty times as much as that of terrestrial mammals (5). Still other studies suggest that the concentration of myoglobin is particularly high in active skeletal muscle. In addition skeletal muscles cells in diving mammals react to hypoxia by increasing the concentration of myoglobin; which not how land mammal cells react. (13)
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Aquatic mammals have more myoglobin in their muscles, allowing them to store more oxygen, thus are able to keep with brains well oxygenated, even during long dives. But what was not clear, until recently, was how all this extra myoglobin existed in the brain of mammals with out clogging the capillaries. Typically when myoglobin concentrations increase, the molecules stick together, clogging capillaries. This can be deadly when those capillaries are in the brain. Aquatic mammals have a unique brand of myoglobin. Dr. Micheal Berenbrink form the Institute of Integrative Biology at the University of Liverpool calls this unique myoglobin "non-stick" myoglobin. (1). This non- stick myoglobin simply has a more positive charge than normal myoglobin, which makes it repel of the myoglobin molecules.