Myoglobin most effectively facilitates oxygen diffusion through muscle cells whe
ID: 166036 • Letter: M
Question
Myoglobin most effectively facilitates oxygen diffusion through muscle cells when the intracellular oxygen partial pressure is comparable to the p_50 value of myoglobin. Explain why. Heart and muscle cells, where myoglobin resides, maintain an intracellular oxygen partial pressure of about 2.5 Torr. Explain why a small change in oxygen partial pressure of 1 Torr in either direction results in a dramatic change in myoglobin oxygen binding. Oxygenated myoglobin is bright red, whereas deoxygenated myoglobin is a purplish color. Myoglobin in which the Fe^2+ has been oxidized to Fe^3+ is referred to as met-myoglobin and appears brown. The sixth ligand in met-myoglobin is water rather than oxygen.Explanation / Answer
Answer 1. Myoglobin effectively binds with oxygen when the intracellular oxygen partial pressure is comparable to P50 of the myoglobin. A shift in the intracellular oxygen partial pressure will deviate the equilibrium with P50 of the myoglobin resulting in dissociation of oxygen from myoglobin.
Answer 2. In metmyoglobin, the iron atom at the center of the myoglobin loses an electron (Fe+2 oxidized to Fe+3) resulting in formation of hemichrome, a brown or tan-colored compound. It is also important to note that the metmyoglobin does not possess the ability to bind oxygen.
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