Identify the two important classes of catalysts. Analyze the chemical reactions that take place when a biological catalyst combines with a reactant (substrate) to form an unstable intermediate.

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Catalysts can be broadly classified into two main categories, homogeneous and heterogeneous. A homogeneous catalyst has the same phase as that of the other substances in the reaction that it aids. Homogeneous catalysts are usually gases or liquids that form a mixture with the reacting substances and there is no boundary of separation between the two. Heterogeneous catalysts on the other hand have a different phase from the substances undergoing a reaction that it is being aided by the catalyst.

Biological catalysts are enzymes that help in allowing certain reactions to take place that in the absence of the catalyst would not occur in the conditions present in biological systems or occur at a rate that is not fast enough to serve its purpose. The substrate forms relatively weak bonds with the enzyme that include hydrogen bonds, weak ionic bonds, and other interactions that are hydrophobic in nature. It is essential that the bond formed between the enzyme and the substrate be a weak one so that after the reaction between the different substrates is complete the resultant can separate from the enzyme easily.

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Identify the two important classes of catalysts.Analyze the chemical reactions that take place when a biological catalyst combines with a reactant (substrate) to form an unstable intermediate.

The two major classes of catalysts are homogeneous catalysts and heterogeneous catalysts.  The homogeneous and heterogeneous refer to the state of the catalyst compared to the state of the substances in the reaction.  For example, a heterogenous catalyst might be a solid which is catalyzing a gas phase reaction.  For a homogeneous catalyst, one could have an aqueous reaction with an aqueous catalyst.

We have catalyzed reactions going on in our body every day.  As the body processes the food we eat, it uses enzymes as catalysts.  A common example of this is lactose (a sugar) and lactase (an enzyme).  For those that are lactose intolerant, they lack enough lactase to process the lactose.  Without the enzyme, the reaction does not happen efficiently and an alternate chemical reaction occurs resulting in gastric distress.

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