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Every Thanksgiving, we are given a graphic view of the difference between slow twitch and fast twitch muscle fibers. Those who like to eat the turkey drumsticks, for example, are eating muscles which have plenty of a darkly-colored protein that is necessary for sustained activity. Typically, the dark meat is comprised of slow-twitch muscles, while the lighter meat has a greater percentage of fast twitch fibers. What is this darkly colored protein?
  1. Tryptophan
  2. Myoglobin
  3. Adenosine tri phosphate (ATP)
  4. Lysine
Explanation
Answer: B - The colored protein that makes muscle appear dark is myoglobin. As muscles contract, they expend their oxygen supply. Myoglobin travels -- with oxygen in tow -- through the blood stream to these muscles allowing them to continue to sustain activity for a longer period of time. In contrast, ATP or adenosine tri phosphate is an enzyme that releases energy. When ATP cleaves off a phosphate, it becomes ADP (or adenosine diphosphate). This loss releases energy.
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