#28 Summary of Enzymes

Enzymes are specialized protein molecules facilitating most of the body’s metabolic processes – such as, supplying energy, digesting foods, purifying your blood, ridding the body of waste products. Enzymes are vital to our health and change the rate at which chemical reactions happen, but without any external energy source added or by being changed themselves.

Things to remember:

• Enzymes are proteins that work as biological catalysts.
• Enzymes are named according to the substrate on which they act. Proteases act on proteins, carbohydrases on carbohydrates and lipases on fats (lipids). The substance that is produced by the reaction is called the product.
• An enzyme molecule has a depression called its active site, which is exactly the right shape for the substrate to fit into. The enzyme can be thought of as a lock, and the substrate as the key.
• Reactions catalysed by enzymes work faster at higher temperatures, up to an optimum that differs for different enzymes. Above the optimum temperature, reaction rate rapidly decreases.
• At low temperatures, molecules have low kinetic energy, so collisions between enzyme and substrate molecules are infrequent. As temperature rises they collide more frequently, increasing reaction rate.
• Above the optimum temperature, the vibrations within the enzyme molecule are so great that it begins to lose its shape. The enzyme is said to be denatured. The substrate no longer fits into the active site and the reaction stops.
• Reactions catalysed by enzymes work fastest at a particular pH. The optimum pH for most enzymes is around pH7 (neutral), but some have an optimum pH much higher or lower than this.
• Extremes of pH cause enzyme molecules to lose their shape, so they no longer bind with their substrate.
• Amylase is found in seeds. When the seed begins to germinate, the amylase is activated and catalyses the breakdown of insoluble starch to soluble maltose in the seed. The maltose is used by the growing embryo as an energy source and to make cellulose for new cell walls.
• Biological washing powders contain enzymes, often obtained from microorganisms such as bacteria or fungi. The enzymes break down proteins or fats on the fabric, forming watersoluble substances that can be washed away.
• Pectinase is used to break down cell walls in fruits, making it easier to extract juice from them.
• The antibiotic penicillin is made by cultivating the fungus Penicillium in a fermenter. The fermenter is kept at the correct pH and temperature for the enzymes of the fungus to work well.