You know from experience that skeletal muscle tires quite quickly, especially if there is not enough oxygen. Interestingly, shellfish such as clams can maintain a month-long contraction in the muscle that keeps the shell closed. No oxygen gets in this situation. These muscles have a different version of myosin called paramyosin. Knowing what you know about the cellular mechanism of muscle contraction, propose a hypothesis to explain how paramyosin might

In muscle cells, myosin molecules continue moving along actin molecules as long as: A. ATP is present and intracellular Ca2+ is high. B. ADP is present and intracellular acetylcholine is high. C. ATP is present and troponin is not bound to Ca2+. D.ATP is present and intracellular Ca2+ is low. E. ADP is present and tropomyosin is released from intracellular stores. QUESTION 27 Lamellipodia and filopodia frequently occur near the edges of cells. These membrane features: A. are supported by intermediate filaments, such as keratin. B. result from the polymerization of actin filaments. C. result from the contraction of actin-myosin. D. probably do not serve any useful purpose to the cell. E. are directly linked to the microtubule organizing center. QUESTION 28 Sort the following events to reflect the sequence during smooth muscle contraction upon delivery of muscle stimu 3. Activation of the myosin light-chain kinase 5. Interaction of myosin head with actin 4. Phosphorylation of myosin 1.…

Myosin binds to actin, then bends. What is ATP needed for next? A. to pump the Ca++ “keys” back into the sarcoplasmic reticulum B. to replace the strap and cover the binding sites C. to give feedback to the neuron that contraction occurred D. to un-bind myosin from actin and re-set for another powerstroke.

A study of muscle fibers between chimpanzees and humans revealed that although muscle mass per body size are approximately equivalent, the ratio of red (slow) and white (fast) fibers were significantly different. Chimps tend to have a ratio of 30% red to 70% white where humans are 60/40 respectively.  Speculate about what this ratio difference means in terms of muscle activity potential and a possible evolutionary significance of this difference.