Velocity is the vector quantity i.e. It needed both direction and magnitude to define it. Velocity is actually the rate of change of subject with respect to some frame reference.
Acceleration is the rate of change of velocity with respect to its velocity. The standard unit of velocity of meter per second square.
Attached is an image of a <span>catechol and a hydroquinone. The specifity of the catechol oxidase is given by the spatial position of the OH groups. Most of the enzymes have an active site that's specific to spatial conformities of the substrate. If the substrate is not in such spatial conformation it may not be recognised be the enzyme.</span>