In the molecule shown in the given diagram, ATPase activity is present in:
   
1. A
2. B
3. C
4. D

What masks the active sites for myosin head present on the actin myofilaments?
1. Light meromyosin
2. Heavy meromyosin
3. G – actin
4. Troponin

Ribs 11 and 12 are called floating ribs because they
1. do not articulate with the vertebrae
2. attach only indirectly to the sternum
3. have no connection to the sternum
4. do not articulate directly with any other bone

The depression on the coxa where the head of the femur articulates is the
1. acetabulum.
2. auricular surface.
3. iliac fossa.
4. ischial tuberosity.

The ability of a muscle fiber action potential to cause an increase in cytosolic calcium concentration is dependent upon
1. The conduction of action potentials down T-tubules which are in intimate contact with the sarcoplasmic reticulum.
2. The presence of the voltage sensitive protein called the ryanodine receptor in the T-tubule membrane
3. The calcium channel protein called the dihydropyridine receptor which is located in the sarcoplasmic reticulum membrane
4. Ca++-ATPase pumps in the sarcoplasmic reticulum

When a skeletal muscle shortens during contraction which of these statements is false?
1. The l-band shortens
2. The A-band shortens
3. The H-zone becomes narrow
4. The sarcomeres shorten

Which of the following is not a feature of red muscle fibres?
1. They have plenty of mitochondria.
2. They have a high content of Myoglobin.
3. They have a high amount of Sarcoplasmic reticulum.
4. They are called aerobic muscles.

During resting stage the binding site of actin for myosin remains masked by
1. Troponin                2. Gactin
3. Tropomyosin          4. Meromyosin

Calcium is important in skeletal muscle contraction because it:
1. Detaches the myosin head from the actin filament.
2. Activates the myosin ATPase by binding to it.
3. Binds to troponin to remove the masking of active sites on actin for myosin.
4. Prevents the formation of bonds between the myosin cross bridges and the actin filament.

A motor unit consists of:
1. A motor neuron and all the muscle fibers innervated by it
2. All the motor neurons innervating one muscle fiber
3. All the muscle fibers in a fasciculus
4. All the muscle fibers in a skeletal muscle