B3.3 Muscle and motility (Organisms, HL): Practice Questions

In the sliding filament theory of muscle contraction, what is the immediate effect of ATP hydrolysis on the myosin head?

A marathon runner primarily relies on a specific type of muscle fiber for sustained aerobic activity. What are the key characteristics of these muscle fibers and why are they advantageous for endurance?

According to the sliding filament theory, what directly happens when a muscle contracts?

When a skeletal muscle fiber undergoes maximal contraction, which of the following changes is observed in the sarcomere structure?

According to the sliding filament theory, identify which regions of the sarcomere decrease in width during a muscle contraction and which region remains unchanged.

How would a failure of the calcium-ATPase pumps on the sarcoplasmic reticulum affect the relaxation phase of a muscle fiber after a contraction?

Explain the specific role of ATP hydrolysis by the myosin head in the molecular mechanism of muscle contraction.

Muscle contraction is a highly coordinated process involving numerous molecular components.

a) Outline the key events that occur at the neuromuscular junction when a motor neuron stimulates a muscle fiber, leading to the generation of an action potential in the muscle fiber.

b) Explain the sliding filament theory of muscle contraction, detailing the roles of actin, myosin, troponin, tropomyosin, ATP, and calcium ions (\(Ca^{2+}\)) in the process.

c) Describe how the binding and hydrolysis of ATP by myosin heads facilitate the movement of actin filaments, resulting in muscle shortening.

The structure of the sarcomere is fundamental to the process of muscle contraction and can be observed via electron microscopy.

a) Identify the proteins that make up the thick filaments and the thin filaments within a myofibril.
b) Explain the sequence of events that occurs after calcium ions (\(Ca^{2+}\)) are released from the sarcoplasmic reticulum until the formation of a cross-bridge.
c) Deduce the effect on the length of the A band and the distance between Z lines when a muscle fiber is stimulated to contract.