Explain the process of skeletal muscle contraction and why glucose is required for this process.
In skeletal muscle there exists a thick filament, myosin, and a thin filament, actin. For contraction both of these filaments need to interact causing a power stroke and muscle contraction. At rest, the myosin and actin are not bound to one another as tropnin is bound to actin and tropomyosin covers the sites where myosin heads interact with actin. Also, at rest the myosin heads are tightly bound to ADP. Following muscle stimulation by a nerve cell, cytosolic calcium levels increase and calcium binds to troponin, inducing a conformational change in actin and exposing the myosin binding site. Myosin heads now bind to actin and shorten the muscle fiber, this is called the power stroke. At the end of the power stroke, ATP binds to myosin, causing the detachment from actin. The ATP molecule is then hydrolysed into ADP and Pi, which releases enough energy to reset the myosin head. Glucose is very important for this process as glucose is the substrate for respiration, the process which produces ATP. Without ATP, the myosin heads would not be able to reset.
