Summary
Highlights
Enzymes are biological catalysts, which are proteins made in living cells that speed up the rate of all metabolic reactions without being changed themselves. They are crucial for life, as they maintain reaction rates necessary for survival, such as in digestion where they break down food molecules quickly.
A substrate is the substance an enzyme acts on, producing products after the reaction. Enzymes have an active site, a specific shape that perfectly fits a particular substrate, forming an enzyme-substrate complex. This specificity is often described as a 'lock and key' mechanism, meaning an enzyme will only act on its complementary substrate.
Temperature significantly influences enzyme activity. As temperature increases, the rate of enzyme-catalyzed reactions generally increases due to higher kinetic energy and more successful molecular collisions. Each enzyme has an optimum temperature where it works best. Above this optimum, enzymes become denatured, meaning their active site changes shape, causing them to stop working. Low temperatures, however, do not denature enzymes but do slow down their activity.
pH is another critical factor affecting enzyme activity. Enzymes have an optimum pH at which they function most effectively. If the pH deviates too much from this optimum, the enzyme can become denatured, changing the shape of its active site and preventing it from binding to its substrate. Different enzymes have different optimum pH levels; for example, pepsin works best at a pH of 2 (acidic conditions in the stomach), while amylase has an optimum pH of 7 (found in saliva).