Main Difference – Catalyst vs Enzyme
Catalyst and enzyme are two substances that increase the rate of a reaction without being changed by the reaction. There are two types of catalysts as enzymes and inorganic catalysts. Enzymes are a type of biological catalysts. The main difference between catalyst and enzyme is that catalyst is a substance that increases the rate of a chemical reaction whereas enzyme is a globular protein that can increase the rate of biochemical reactions. The inorganic catalysts include mineral ions or small molecules. In contrast, enzymes are complex macromolecules with 3D structures. Enzymes are specific and work in mild conditions.
Key Areas Covered
1. What is a Catalyst
– Definition, Characteristics, Examples
2. What is an Enzyme
– Definition, Characteristics, Examples
3. What are the Similarities Between Catalyst and Enzyme
– Outline of Common Features
4. What is the Difference Between Catalyst and Enzyme
– Comparison of Key Differences
Key Terms: Activation Energy, Biological Reactions, Catalyst, Chemical Reactions, Cofactors, Enzyme, Inorganic Catalysts, pH, Reaction Rate, Temperature
What is a Catalyst
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
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.
What is an Enzyme
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 4,000 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 function of the enzymes is highly specific. Most of the enzymes are made up of globular proteins with high molecular weights. The globular proteins are rearranged into multi-protein complexes. Some enzymes require the assistance of cofactors for their action. Cofactors are inorganic ions such as Mg2+, Fe2+, Zn2+, and Mn2+ or small organic molecules called co-enzymes. The enzyme can be inhibited or activated by the binding of cofactors to the enzyme.
Figure 3: Glucosidase Enzyme
Enzymes are classified into six types based on the type of reaction they catalyzed. They are oxidoreductases, transferases, lyases, hydrolases, ligases, and isomerases. The enzyme glycosidase, which converts maltose into two glucose molecules, is shown in figure 3.
Similarities Between Catalyst and Enzyme
- Both catalyst and enzyme increase the rate of a chemical reaction by lowering the activation energy.
- Both catalyst and enzyme are not changed by the reaction.
- Both catalyst and enzyme temporary bind to their substrates.
- The rate of both forward and backward reactions are increased by catalysts and enzymes.
- Both catalyst and enzyme have no effect on the equilibrium constant of the reaction.
Difference Between Catalyst and Enzyme
Definition
Catalyst: A catalyst is a substance that increases the rate of a chemical reaction, without undergoing any permanent chemical change.
Enzyme: An enzyme is a biological molecule produced by living organisms, which catalyzes a specific biochemical reaction at body temperatures.
Correlation
Catalyst: Catalyst can be either inorganic catalysts or enzymes.
Enzyme: Enzymes are a type of a catalyst.
Type
Catalyst: Inorganic catalysts are mineral ions or small molecules.
Enzyme: Enzymes are globular proteins.
Size Difference
Catalyst: Inorganic catalysts are similar in size to the substrate molecules.
Enzyme: Enzymes are quite larger than the substrate molecules.
Molecular Weight
Catalyst: Inorganic catalysts have a low molecular weight.
Enzyme: Enzymes have a high molecular weight.
Action
Catalyst: Inorganic catalysts act on physical reactions.
Enzyme: Enzymes act on biochemical reactions.
Efficiency
Catalyst: Inorganic catalysts are less efficient.
Enzyme: Enzymes are highly efficient.
Specificity
Catalyst: Inorganic catalysts can increase the rate of a diverse set of reactions.
Enzyme: Enzymes can only increase the rate of a specific reaction.
Regulator Molecules
Catalyst: The function of inorganic catalysts is not controlled by regulator molecules.
Enzyme: The function of enzymes can be regulated by the binding of regulator molecules with the enzyme.
Temperature
Catalyst: Inorganic catalysts function at high temperatures. They are not sensitive to small temperature changes.
Enzyme: Enzymes operate at a specific temperature. At low temperatures, they are inactive, and at high temperatures, they get denatured.
pH
Catalyst: Inorganic catalysts are not sensitive to small changes in pH.
Enzymes: Enzymes operate only at a specific range of pH.
Pressure
Catalyst: Typically, Inorganic catalysts operate at high pressure.
Enzyme: Enzymes operate at normal pressure.
Protein Poisons
Catalyst: Protein poisons have no effect on the inorganic catalysts.
Enzymes: Enzymes can be poisoned by protein poisons.
Short Wave Radiation
Catalyst: Short wave radiations have no influence on the inorganic catalysts.
Enzymes: Enzymes can be denatured by short wave radiations.
Examples
Catalyst: Vanadium (V) oxide, iron, and platinum are examples of inorganic catalysts.
Enzyme: Amylase, lipase, Glucose-6-phosphatase, Alcohol dehydrogenase, and Aminotransferases are the examples of enzymes.
Conclusion
Catalyst and enzyme are substances that increase the rate of a chemical reaction by lowering the activation energy. However, they are not affected or changed by the reaction. Catalysts can be either inorganic catalysts or enzymes. Inorganic catalysts are metal ions or small molecules, which catalyze the chemical reactions out of the living organisms. Enzymes are biological macromolecules, which catalyze specific biochemical reactions inside the living organisms. Enzymes only work in mild conditions. The main difference between catalyst and enzyme is the form of the catalysts, substrates, and their mode of catalyzing reactions.
Reference:
1.“What is a Catalyst?” School Chemistry, Available here. Accessed 18 Aug. 2017.
2.“What is an enzyme?” About Enzymes | AMANO, Available here. Accessed 18 Aug. 2017.
3. Phillips, Theresa. “Defining Enzyme Structure and Function.” The Balance, Available here. Accessed 18 Aug. 2017.
Image Courtesy:
1. “CatalysisScheme” By No machine-readable author provided. Smokefoot assumed. Own work assumed (based on copyright claims) (Public Domain) via Commons Wikimedia
2. “Vanadium pentoxide powder” By W. Oelen – (CC BY-SA 3.0) via Commons Wikimedia
3. “Glucosidase enzyme” By Thomas Shafee – Own work (CC BY-SA 4.0) via Commons Wikimedia
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