-substrate complex. The enzymes emerge from the reaction in their original form and are ready to function over and over again. When a reaction rearranges the atoms of molecules, the bonds in the reactants must be broken and the new bonds in the products must be formed. This requires energy. The energy required to break the bonds in the reactant molecules is known as the activation energy. The bonds only break when the molecule has absorbed enough energy (usually in the form of heat) to become unstable. Heat speeds up a reaction, but the high temperature kills cells. Organisms must instead use a catalyst. Enzymes (mostly proteins) are biological catalysts. Enzymes speed up reactions by lowering the barrier of activation energy, so that the transition state is within reach at regular temperatures. A transition state occurs when reactants are in an unstable condition and are ready for the reaction to

Some common words found in the essay are:
, active site, rate reaction, substrate enters active, substrate enzyme, enters active site, complex enzymes, activation energy, enters active, induced fit, substrate enters, environmental conditions, enzyme activity,
Approximate Word count = 607
Approximate Pages = 2 (250 words per page double spaced)