What is the role of calcium in muscle contraction?a. Its binding to a regulatory protein causes the protein to move, exposing actin binding sites to the myosin heads.b. It provides energy for contraction.c. It blocks contraction when the muscle relaxes.d. It forms the heads of the myosin molecules in the thick filaments inside a muscle fiber.

How did data on sarcomere structure inspire the sliding-filament model of muscle contraction? Explain why the observation that muscle cells contain many mitochondria and extensive smooth endoplasmic reticulum turned out to be logical once the molecular mechanism of muscular contraction was understood.

Which of the following animals is correctly matched with its type of skeleton?a. fly—endoskeletonb. earthworm—exoskeletonc. lobster—exoskeletond. bee—hydrostatic skeleton

Rigor mortis is the stiffening of a body after death that occurs when myosin binds to actin but cannot unbind. What prevents myosin from unbinding?

When a dog is running fast, its body position is stabilized bya. side-to-side undulation.b. energy stored in tendons.c. foot contact with the ground.d. its momentum.

Muscle A and muscle B have the same number of fibers, but muscle A is capable of more precise control than muscle B. Which of the following is likely to be true of muscle A? (Explain your answer.)a. It is controlled by more neurons than muscle B.b. It contains fewer motor units than muscle B.c. It is controlled by fewer neurons than muscle B.d. It has larger sarcomeres than muscle B.

Which of the following statements about skeletons is true?a. Chitin is a major component of vertebrate skeletons.b. Loss of forelimbs in snakes involved little change in the axial skeleton.c. Most cnidarians must shed their skeleton periodically to grow.d. Vertebrate bones contain living cells.

In terms of both numbers of species and numbers of individuals, insects are the most successful land animals. Write a paragraph explaining how their exoskeletons help them live on land. Are there any disadvantages to having an exoskeleton?

Distance runner Paula Radcliffe has won dozens of long-distance races and held the women's world record for the marathon since 2003. Scientists, trainers, and athletes alike have wondered about the extent to which muscle structure and function contribute to success in athletes such as Radcliffe. What makes elite distance runners so good? Are their muscles somehow different from those of less successful athletes and non-athletes?Compare and contrast the structure and function of the three types of skeletal muscle fibers.