IFPA Trainer Practice Exam

The head of the myosin filament, which is bound to the high energy molecule ______, adds water (hydrolyzes) to form a high energy complex including ______ and inorganic ______.

1. ADP, ATP, CP

2. ATP, AMP, Ca2+

3. ATP, ADP, Ca2+

4. Adenosinetriphosphate; ADP; phosphate

The correct answer is: Adenosinetriphosphate; ADP; phosphate

The correct answer emphasizes the biochemical processes involved during muscle contraction. The head of the myosin filament binds to ATP (adenosinetriphosphate), which is a high-energy molecule. During the muscle contraction cycle, the myosin head hydrolyzes ATP, breaking it down into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This reaction releases energy, which causes the conformational change in myosin that enables it to pull on actin, thus facilitating muscle contraction. Choosing the term "adenosinetriphosphate" rather than simply "ATP" is a precise way to reference the molecule involved. The formation of a high energy complex including ADP and inorganic phosphate is an important part of the process that occurs after the hydrolysis of ATP, highlighting the intricate relationship between energy transfer and muscle dynamics. In the other options, while some of the components are mentioned, they do not accurately reflect the main molecules involved in muscle contraction. For instance, AMP is not a direct product of ATP hydrolysis in this context, and while Ca2+ plays a role in muscle contraction, it is not produced from the hydrolysis of ATP. Therefore, the statement correctly encapsulates the key biochemical events surrounding myosin