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Kaplan Qbank USMLE



Author4 Posts
  #1

fast twitch fibres can either use aerobic (slow) or anaerobic (fast) ATP production pathways...

How can a fast twitch fibre be fast if its using oxidative phosphorylation to produce ATP (doesn't that take much longer than glycolysis & PCr phosphorylation etc?)

thanks



  #2

As far as I know, fast fibres are also called white fibers and they have much glicogen, low mioglobin, low blood supply and perform glycolisis.
But it doesn't mean that they have no mitochondria, the truth is they have few mitochondria but they have, I suppose that they use mitochondria during resting state, because they are not enough quick during contraction.
Slow or red fibers have many blood vessels, mitochondria, myoglobin etc so they use aerobic ATP production.

  #3

What I wanted to say is that generally fast fibres use anaerobic metabolism and slow fibres use aerobic metabolism but it doesn't mean that they aren't capable of using other way

  #4

thanks, i thought that might have been the case - my textbook was pretty vague with the explination!







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