Enzymes

The shape allows smaller chemicals (substrate molecules) to fit into certain places called active sites. This brings the substrate chemicals close together and so they can react more easily than they would do otherwise.

Enzymes work best at specific temperatures and pH levels, for example, human enzymes work best at about 37^oC. They are sensitive to temperature and pH, and change their shape under conditions of moderately high temperatures (45^oC and above) and values of pH that differ from the ones in which they normally work. When they change shape like this, we say that they are denatured and the active sites will no longer work as efficiently. As the temperature or pH becomes more extreme, the active sites stop working altogether.

Enzymes are found at work in almost all places in the body of any organism, whether plant, animal or bacteria. They are catalysts for many biological processes such as respiration, photosynthesis and the synthesis of proteins. They also break down longer molecules into shorter more useful chemicals e.g. during digestion, enzymes convert large molecules into smaller molecules which can then be absorbed. Because they can be used to cut other molecules, they are used in genetic engineering. They are carefully chosen to cut specific genes from the DNA of plants and animals which can then be spliced into other DNA. They are even used in industry to catalyze reactions at normal pressure and temperature thus saving money on expensive energy-demanding equipment that would otherwise be needed.

Try this quiz and test your knowledge of enzymes - the proteins and biological catalysts.