Enzyme unit SI unit, the enzyme unit is discouraged in favour of the katal, the unit recommended by the General Conference on Weights and Measures in 1978 and officially adopted in 1999. One katal is the amount of enzyme that converts 1 mole of substrate per second, so The enzyme unit should not be confused with the international unit (IU); although it is true that both measure chemical activity and that for many enzymes 1 U = 1 IU (because for many enzymes the existing U was adopted as the newer IU), international units can be defined for the biologic activity of
Action (physics) in time and space. Action has the dimensions of [energy]⋅[time], and its SI unit is joule-second, which is identical to the unit of angular momentum. In classical physics, the term "action" has a number of meanings. Most commonly, the term is used for a functional formula_2 which takes a function of time and (for fields) space as input and returns a scalar. In classical mechanics, the input function is the evolution q("t") of the system between two times "t" and "t", where q represents the generalized coordinates. The action formula_3 is defined as the integral of the Lagrangian "L" for