Proteins are transported via axoplasmic transport at slow rates (0.5 to 2 mm per day) and fast rates (200 to 400 mm per day). the difference in transport rate directly results from:
a. the difference in the time spent per day in transport by kinesin on microtubules.
b. the site where the protein is synthesized
c. the substrate molecule used by the motor protein
d. the motor protein used to transport the proteins

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.