A reaction that involves more than one @E02035@ is said to occur by a @CT07545@ mechanism. The terms @C01205@, @I03011@ mechanism, and @S05970@ mechanism are also commonly used. There are two main kinds of evidence for a @CT07545@ mechanism:
Reactions occurring in parallel, such as: Reactions occurring in forward and reverse directions are called @O04302@: Reactions occurring in @ST06775@, such as Reactions are said to exhibit feedback if a substance formed in one step affects the rate of a previous step. For example, in the scheme: @C00960@
- The kinetic equation for the reaction does not correspond to its @S06026@.
- There is experimental evidence, direct or indirect, for intermediates of such a nature that it is necessary to conclude that more than one @E02035@ is involved.
C01210-2.pngare called @P04403@ or @S05680@. When there are @S05680@ there is sometimes @C01198@, as in the scheme:
C01210-4.pngwhere B and C compete with one another for A.
C01210-6.pngare known as @C01276@.
C01210-6.pngThe intermediate Y may catalyse the reaction C01210-7.png (@P04767@) or it may inhibit it (negative feedback).