Chapter 8 Self-test questions

. Which of the following statements about the structure of skeletal muscle is correct?

Individual myofibrils of skeletal muscle cells contain numerous myofibres.

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

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

During contraction thick myosin filaments are pulled towards the centre of the sarcomere.

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

Thick myosin filaments of skeletal muscle have plus and minus ends.

Thin actin filaments of skeletal muscle have plus and minus ends.

Thin actin filaments of skeletal muscle have globular heads.

Thin actin 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?

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

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

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

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?

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

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

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

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

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

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

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

. Which of the following statements about actin polymerisation and actin binding proteins is correct?

Actin monomers can only bind to the (+) end of an actin filament.

Actin polymerization requires hydrolysis of ATP.

Capping proteins bind the ends of actin filaments and stimulate depolymerization.

Gelsolin severs actin filaments and stimulates depolymerization.

. Which of the following statements about microtubules is correct?

â tubulin has latent ATPase activity, which regulates microtubule stability.

Microtubules are hollow tubes consisting of 13 protofilaments.

Microtubules are polymers of â tubulin homodimers.

Microtubules are stable structures in the cell.

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

Skeletal muscle contracts slowly.

Skeletal muscle has a striated appearance under the microscope.

Skeletal muscle can maintain its contraction for long periods.

Skeletal muscle is controlled by involuntary nervous action.

. Which of the following statements about creatine phosphate is correct?

Creatine phosphate is essential in muscle cells for contraction to occur.

Creatine phosphate is stored in muscle cells unlike ATP.

Like ATP, creatine phosphate cannot be stored in muscle cells.

Creatine phosphate is converted to creatinine by creatine kinase.

. Which of the following statements about the thick filaments of striated skeletal muscle is correct?

A thick filament is made up of two fibres with the same polarity wound around each other.

A thick filament is made up of two heavy polypeptide chains arranged in a coiled-coil around each other.

A thick filament contains hundreds of myosin molecules with the heads pointing towards the centre of a sarcomere.

A thick filament contains hundreds of myosin molecules arranged in a bipolar fashion.

. Which of the following statements about the control of contraction in skeletal muscles is correct?

In skeletal muscles, contraction is initiated by a nerve impulse closing voltage-gated Ca ²⁺ channels in the plasma membrane.

In skeletal muscles, contraction is initiated by a nerve impulse opening voltage-gated Ca²⁺ channels in the plasma membrane.

In skeletal muscles, contraction is initiated by a nerve impulse closing voltage-gated Ca ²⁺ channels in the sarcoplasmic reticulum membrane.

In skeletal muscles, contraction is initiated by a nerve impulse opening voltage-gated Ca²⁺ channels in the sarcoplasmic reticulum membrane.

. Which of the following statements about the mechanism of skeletal muscle contraction are correct? Please select all that apply.

Skeletal muscle contraction occurs when the myosin head hydrolyses ATP.

Skeletal muscle contraction occurs when the myosin head binds to the actin filament.

Skeletal muscle contraction occurs when the myosin head binds ATP.

Skeletal muscle contraction cannot occur when the myosin head is bound to ATP.

Chapter 8 Self-test questions

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