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Which of the following statements about the structure of skeletal muscle is not correct?

a) Myofibres of skeletal muscle cells contain numerous myofibrils that are divided into sarcomeres.

b) The arrangement of thick myosin and thin actin filaments give the sarcomeres of skeletal muscle a striated appearance under the microscope.

c) In skeletal muscle Z discs of proteins at each end of the sarcomeres have the actin filaments attached to them.

d) The arrangement of thin myosin and thick actin filaments give the sarcomeres of skeletal muscle a striated appearance under the microscope.

Which of the following statements about the structure of the thick and thin filaments in skeletal muscle is correct?

a) Thick filaments of skeletal muscle have plus and minus ends.

b) Thin filaments of skeletal muscle have plus and minus ends.

c) Thin filaments of skeletal muscle have globular heads.

d) Thin filaments of skeletal muscle are held in the correct orientation by the protein titin.

Which of the following statements about the contraction of skeletal muscle is correct?

a) The power stroke of skeletal muscle contraction occurs when the myosin head hydrolyses ATP.

b) The power stroke of skeletal muscle contraction occurs when the myosin head binds ATP.

c) The power stroke of skeletal muscle contraction occurs when the myosin head releases ATP.

d) The power stroke of skeletal muscle contraction occurs when the myosin head releases ADP and Pi.

Which of the following statements about the role of calcium (Ca²⁺) during skeletal muscle contraction is correct?

a) Ca²⁺released into a myofibril by the action of a nerve impulse binds to a site on the myosin head to initiate contraction.

b) Ca²⁺released into a myofibril by the action of a nerve impulse binds to a site on tropomyosin to initiate contraction.

c) Ca²⁺released into a myofibril by the action of a nerve impulse binds to a site on the actin to initiate contraction.

d) Ca²⁺released into a myofibril by the action of a nerve impulse binds to a site on troponin to initiate contraction.

Which of the following statements about smooth muscle contraction is correct?

a) A Ca²⁺-calmodulin complex activates the phosphatase that causes contraction of smooth muscle.

b) Unlike striated muscle, contraction of smooth muscle cells occurs when Ca²⁺levels fall.

c) Phosphorylation of a myosin light chain allows actin-myosin binding in smooth muscle.

d) Dephosphorylation of a myosin light chain allows actin-myosin binding in smooth muscle.

Oxford University Press, Online Resource Centre, Chapter 08.