How is catalyst like platinum different from an enzyme

What is a Catalyst — Definition, Characteristics, Examples 2. What is an Enzyme — Definition, Characteristics, Examples 3. A catalyst is a substance that allows chemical reactions to occur either at a faster rate or under different conditions. Typically, a very small amount of catalysts is required for a reaction.

In general, catalysts decreases the activation energy of a reaction by introducing an alternative pathway to the reaction. Catalysts react with the substrate to form a temporary intermediate at a low energy state.

The two types of catalysts are inorganic catalysts and enzymes. The effect of a catalyst on the activation energy of a reaction is shown in figure 1. Figure 1: Effect of a catalyst on the activation energy of a reaction. Inorganic catalysts can be either a transition metal or a transition metal oxide. The transition metals consist of a broad specificity. They provide a convenient area surface to the chemical reaction to occur in different routes. This different route lowers the activation energy of the chemical reaction.

Metal catalysts are generally used as fine powders with a bigger surface area. Inorganic catalysts can be classified based on the nature of the substance as homogeneous catalysts and heterogeneous catalysts. Figure 2: Vanadium V oxide. Homogeneous catalysts are in the same phase with its substrate. For example, the gaseous phase substrates are catalyzed by gaseous phase catalysts.

The heterogeneous catalysts are not in the same phase as the substrates. For example, iron is a metal used to produce ammonia from nitrogen and hydrogen. Platinum is used to produce nitric acid from ammonia. Vanadium V oxide is used to produce sulfuric acid. Vanadium V oxide powder is shown in figure 2. An enzyme is a biological macromolecule produced by living organisms to catalyze the biochemical reaction inside the cell at body temperatures.

The function of an enzyme is indispensable to the maintenance of life. All biochemical reaction occurring in living organisms depend on catalysts.

Up to now, the action of around 4, enzymes are well known. Enzymes act in mild conditions such as body temperature and pH. They catalyze the reactions of building and breakdown of materials inside the living organisms. The activation energy is the difference between the energy of the starting reagents and the transition state—a maximum on the reaction coordinate diagram. The reagents are at 6 kJ and the transition state is at 20 kJ, so the activation energy can be calculated as follows:. Check Your Learning Determine which of the two diagrams here both for the same reaction involves a catalyst, and identify the activation energy for the catalyzed reaction:.

Diagram b is a catalyzed reaction with an activation energy of about 70 kJ. A homogeneous catalyst is present in the same phase as the reactants. It interacts with a reactant to form an intermediate substance, which then decomposes or reacts with another reactant in one or more steps to regenerate the original catalyst and form product.

Ozone in the upper atmosphere, which protects the earth from ultraviolet radiation, is formed when oxygen molecules absorb ultraviolet light and undergo the reaction:. Ozone is a relatively unstable molecule that decomposes to yield diatomic oxygen by the reverse of this equation. This decomposition reaction is consistent with the following mechanism:. The presence of nitric oxide, NO, influences the rate of decomposition of ozone.

Nitric oxide acts as a catalyst in the following mechanism:. The nitric oxide reacts and is regenerated in these reactions. It is not permanently used up; thus, it acts as a catalyst. The rate of decomposition of ozone is greater in the presence of nitric oxide because of the catalytic activity of NO. Certain compounds that contain chlorine also catalyze the decomposition of ozone.

Crutzen, Mario J. Molina Figure 3 , and F. The ozone layer protects earth from solar radiation by absorbing ultraviolet light. The work of Molina and Rowland was instrumental in the adoption of the Montreal Protocol, an international treaty signed in that successfully began phasing out production of chemicals linked to ozone destruction.

Molina and Rowland demonstrated that chlorine atoms from human-made chemicals can catalyze ozone destruction in a process similar to that by which NO accelerates the depletion of ozone.

Chlorine atoms are generated when chlorocarbons or chlorofluorocarbons—once widely used as refrigerants and propellants—are photochemically decomposed by ultraviolet light or react with hydroxyl radicals.

A sample mechanism is shown here using methyl chloride:. Chlorine radicals break down ozone and are regenerated by the following catalytic cycle:. A single monatomic chlorine can break down thousands of ozone molecules. Luckily, the majority of atmospheric chlorine exists as the catalytically inactive forms Cl 2 and ClONO 2.

Enzymes in the human body act as catalysts for important chemical reactions in cellular metabolism. As such, a deficiency of a particular enzyme can translate to a life-threatening disease. G6PD glucosephosphate dehydrogenase deficiency, a genetic condition that results in a shortage of the enzyme glucosephosphate dehydrogenase, is the most common enzyme deficiency in humans. A disruption in this pathway can lead to reduced glutathione in red blood cells; once all glutathione is consumed, enzymes and other proteins such as hemoglobin are susceptible to damage.

For example, hemoglobin can be metabolized to bilirubin, which leads to jaundice, a condition that can become severe. People who suffer from G6PD deficiency must avoid certain foods and medicines containing chemicals that can trigger damage their glutathione-deficient red blood cells.

A heterogeneous catalyst is a catalyst that is present in a different phase usually a solid than the reactants. Such catalysts generally function by furnishing an active surface upon which a reaction can occur.

Gas and liquid phase reactions catalyzed by heterogeneous catalysts occur on the surface of the catalyst rather than within the gas or liquid phase. Any one of these steps may be slow and thus may serve as the rate determining step. In general, however, in the presence of the catalyst, the overall rate of the reaction is faster than it would be if the reactants were in the gas or liquid phase.

A catalyst is some material that speeds up chemical reactions. With a helping hand from a catalyst, molecules that might take years to interact can now do so in seconds. Factories rely on catalysts to make everything from plastic to drugs. Catalysts help process petroleum and coal into liquid fuels.

Natural catalysts in the body — known as enzymes — even play important roles in digestion and more. During any chemical reaction, molecules break chemical bonds between their atoms. The atoms also make new bonds with different atoms.

This is like swapping partners at a square dance. Sometimes, those partnerships are easy to break. A molecule may have certain properties that let it lure away atoms from another molecule. But in stable partnerships, the molecules are content as they are. Left together for a very long period of time, a few might eventually switch partners. Catalysts make such a breaking and rebuilding happen more efficiently. They do this by lowering the activation energy for the chemical reaction. Activation energy is the amount of energy needed to allow the chemical reaction to occur.