Motor Proteins and Directed Movement Along Tracks · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
به انگلیسی

Motor cycles and track direction

Science · Organisms & Life Processes · ages 20-22
Name ______________________   Date ____________

  1. Conventional kinesin-1 usually carries cargo toward which microtubule end?

    • Toward the track's minus end
    • Toward neither end of the track
    • Toward the track's plus end

  2. What happens when ATP binds to a muscle myosin head attached to actin?

    • The head immediately performs its pulling power stroke
    • The head releases its attachment to actin
    • The head resets before releasing its actin attachment

  3. Myosins use actin tracks, while kinesins and dyneins use microtubule tracks.

    Circle one:   True   False

  4. ATP has bound and released a muscle myosin head from actin. A treatment now prevents that head from hydrolyzing ATP. Which stage is directly impaired?

    • Releasing the head when ATP first binds
    • Exposing actin sites when calcium binds troponin
    • Resetting the head for another cycle

  5. A microtubule has its plus end at the cell edge and minus end at the center. Which motor can carry a vesicle from edge to center?

    • Conventional kinesin-1 on this track
    • Muscle myosin on this microtubule
    • Cytoplasmic dynein on this track

  6. Calcium rises in a skeletal muscle fiber while ATP is available. How does calcium permit myosin cycling?

    • It binds myosin, which directly shifts tropomyosin off the sites
    • It binds troponin, shifting tropomyosin away from the sites
    • It binds actin directly, displacing troponin from the filament

  7. Only actin-based motors can transport cargo near a cell membrane.

    Circle one:   True   False

  8. A microtubule has its plus end at the center and minus end at the edge. Cytoplasmic dynein carries cargo along it. Which way does the cargo travel?

    • Toward the edge, where the minus end lies
    • Toward the center, where the plus end lies
    • Toward the center because dynein must always travel inward
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Motor cycles and track direction W1-mt_TUTmILr7y0-s1

  1. Toward the track's plus end · Conventional kinesin-1 is usually plus-end directed. That direction does not describe every kinesin-family member.
  2. The head releases its attachment to actin · ATP binding causes detachment. Hydrolysis resets the released head; the power stroke occurs later in the cycle.
  3. True · The track-family matches are correct. They do not establish an exclusive rule about travel distance.
  4. Resetting the head for another cycle · ATP hydrolysis resets the released myosin head. Blocking hydrolysis directly impairs that reset, rather than reversing the release that already occurred.
  5. Cytoplasmic dynein on this track · The destination is the minus end. Cytoplasmic dynein moves toward that end.
  6. It binds troponin, shifting tropomyosin away from the sites · Calcium binds troponin. The resulting change shifts tropomyosin away from myosin-binding sites on actin.
  7. False · Local actin transport is common, but location alone does not exclude microtubule-based transport.
  8. Toward the edge, where the minus end lies · Dynein follows the minus-end direction. Here the minus end is at the edge, so spatial travel is outward.
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