1.  Actin and myosin are directly involved in muscle contraction. They are some of the proteins that are necessary to maintain the structural integrity and function of the sarcomere. Actin is the most abundant protein in the typical eukaryotic cell. This protein is highly conserved, and forms a huge variety of structure in cells in concert with a huge numbers of actin binding proteins. Myosins are a large family of  Motor proteins motor proteins and are responsible for Actin actin-based  Motility motility. Each myosin molecule has a tail which forms the core of the thick myofilament plus a head that projects out from the core of the filament. Contact with actin causes the myosin head to swivel. During the swivel, the myosin head is firmly attached to actin and thus the binding of the two filaments. If under certain circumstances that the two myofilaments are extracted and placed in a beaker, the molecule that must be added to the beaker to make the filaments unbind is Adenosine triphosphate (also known as ATP). Since, at the end of the swivel of a myosin head, it fits into the binding site on the cross-bridge  this breaks the bond between the cross-bridge (myosin) and actin, resulting in the eventual unbinding of both proteins.

2.  Different types of athletes usually have a unique composition of muscle tissue in their body, that being the kind that suits their sport the best. The difference of enzyme activity or the concentration of substances in the muscle tissues depends on the nature of the activities that they perform. In examining biopsies taken from the gastrocnemius muscles of the athletes, the researcher would notice that the succinate dehydrogenase (SDH) activities were highest and the percentage of slow twitch fibers are most predominant among the 10,000m runners followed by the 100m dash athletes then the weight lifting athletes. Oxidative capacity of slow twitch and fast twitch fiber types was also greater in the 10,000m dash athletes than in the other groups of athletes.

3.  Given the symptoms, it means that Speedy sprinter has no ability to raise her right heel off the ground while her toes are in contact with the ground. She is still able to turn or move the forepart of her foot away from the midline of her body. Her ability to bring the dorsal surface or the top part of her foot towards the anterior surface of the leg is more than normal. Meaning, she can flex her foot further than most people can with ease. Her calf muscles, on the other hand, were said to be bulging. Injury to the calf muscles is very common in athletes. The muscles may become inflamed from being torn due to a sudden impact or due to overuse. In the case of Speedy sprinter, anti-inflammatory drugs and physical therapy may be necessary because these symptoms may lead to more complex problems if not treated correctly.


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