Molecular motors are formed by?

Ans. D. All of the abovea. The molecular motors that move proteins, organelles, and other cell parts (collectively referred to as "cargo") to all parts of the cell are 100 to 500 kDa ATPases.b. They attach to their cargo at one end of the molecule and to microtubules or actin polymers with the other end, sometimes referred to as the "head." They convert the energy of ATP into movement along the cytoskeleton, taking their cargo with them. There are three super families of molecular motors:c. kinesin, dynein, and myosin. It is important to note that there is extensive variation among superfamily members, allowing for specialization of function (eg, choice of cargo, cytoskeletal filament type, and/or direction of movement).d. The conventional form of kinesin is a double headed molecule that tends to move its cargo toward the "+" ends of microtubules. One head binds to the microtubule and then bends its neck while the other head swings forward and binds, producing almost continuous movement. Some kinesins are associated with mitosis and meiosis. Other kinesins perform different functions, including, in some instances, moving cargo to the "-"end of microtubules. Dynein's have two heads, with their neck pieces embedded in a complex of proteins. Cytoplasmic dynein's have a function like that of conventional kinesin, except they tend to move particles and membranes to the "-" end of the microtubules. The multiple forms of myosin in the body are divided into 18 classes,e. The heads of myosin molecules bind to actin and produce motion by bending their neck regions (myosin II) or walking along microfilaments, one head after the other (myosin V). In these ways, they perform functions as diverse as contraction of muscle and cell migration.