回顧問題不定期更新 Study Questions are Made by Prof. Cruz & Prof. Moore from Oberlin College & Conservatory?

Lectures 32 and 33: Muscles & Locomotion?

1. Explain why there is such a thing as plant movements but no such thing as plant locomotion.?

2. Define: myofiber, myofibril, sarcolemma, thin filament, thick filament, and sarcoplasmic reticulum. What is the function of each in muscle contraction??

3. Make a sketch (from memory!) of a sarcomere, being careful to label all the known regions (bands, lines, zones). List the protein(s) you would expect to find in each region.?

4. During myofiber contraction, which filaments are “sliding”, where are they going, and how does this explain a muscle contracting, say one of the muscles between the joints in your little finger?

5. Which of the proteins in a sarcomere would be the best candidate for the “Switch Protein”? Explain your answer. Switch here refers to the initiation of a muscle contraction (‘turning it on’).?

6. Define power stroke and cross-bridge.?

7. How would sarcomere shortening be affected if?

a) all the myosin heads were oriented exactly the same, going the same way??

b) the Z line were defective??

c) troponin had a mutated series of amino acids in its active site??

d) Ca++ channels in the SR were blocked??

e) Ca++ somehow flowed freely into the cytoplasm all the time??

f) the openings of some T tubules were blocked?

8. A corpse stiffens after death (‘rigor mortis’, stiffness of death) because the myosin heads in the skeletal myofibers remain attached to actin. (Normally, the myosin heads detach, right?) Explain what has happened so that now the myosin heads cannot detach.?

9. One of the most dangerous neurotoxins known is tetrodotoxin, which is found in the puffer fish (also called fugu, for connoisseurs of Japanese fine cuisine). One microgram of this toxin is the mortal dose for a person. Shown below is the mechanism of action for tetrodotoxin, which kills its victim indirectly: by asphyxiation, because the diaphragm muscles cannot receive action potentials. Explain to your roommate why he or she should be very careful when choosing fugu from a menu in a fancy Japanese restaurant.

Note that tetrodotoxin blocks sodium channels only, not K+ channels. In this diagram, sodium ions (Na+) are shown linked to a negatively charged ion (OH-)2. It should not affect your answer.

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離久-張所長