myglobin - vessels When tissue P O2 values are low and...

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Muscle cells have their own oxygen-binding molecule, myoglobin. Myoglobin consists of just one polypeptide chain associated with an iron-containing ring structure that can bind one molecule of O 2 . Myoglobin has a higher affinity for O 2 than hemoglobin does, so it picks up and holds O 2 at P O2 values at which hemoglobin is releasing its bound O 2 (Figure 48.13). Myoglobin facilitates the diffusion of O 2 in muscle cells and provides a reserve of O 2 for times when metabolic demands are high and blood flow is interrupted. Interruption of blood flow in muscles is common because contracting muscles squeeze blood
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Unformatted text preview: vessels. When tissue P O2 values are low and hemoglobin can no longer supply more O 2 , myoglobin releases its bound O 2 . Diving mammals such as seals have high concentrations of myoglobin in their muscles, which is one reason they can stay under water for so long. (We will learn more about adaptations for diving in the next chapter.) Even in nondiving animals, muscles called on for extended periods of work frequently have more myoglobin than muscles that are used for short, intermittent periods, as we saw in the previous chapter....
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