Cells are possibly the smallest chemical factories in the world and yet they are exquisitely efficient and productive. They build chemical compounds (anabolism) from imported raw materials and break down larger molecules (catabolism) to access the necessary elements and energy to help maintain proper function. Cellular chemical processes are referred to as metabolism.
Metabolic reactions require a great amount of energy to take place (activation energy or EA). One way cells manage metabolic reactions is through the presence of enzymes. Enzymes are a type of protein that helps control and manage cell metabolism by making chemical reactions happen more efficiently than if the cell functioned without them. Enzymes lower the activation energy normally required for chemical reactions to take place.
Enzymes compounds are three-dimensional molecules that have special bonding areas called active sites. At the active site of some enzymes, large molecules are broken into smaller molecules (catabolism). Other enzymes bond small molecules together to make larger compounds (anabolism). The molecules and enzymes metabolizes are known as substrates.
The shape of an enzyme's active site is matched to the shape of the molecule it metabolizes. The substrate bonds to the active site and the enzyme molecule firms up the attachment. If possible, take a moment to shake hands with someone. The way hands fit together and firm up in a hand shake is similar to how an enzyme-substrate complex bonds. This is called an "induced fit."
Enzymes function best in specific conditions; environmental factors within the cell can affect how well an enzyme functions. High temperatures can denature (break down) an enzyme, changing its shape. Most enzymes work best in environments where pH range is 6 - 8. Higher or lower values in cells negatively affect enzyme function and thus cell function. An exception is digestive enzymes in the human stomach, which work best in pH 2. Some enzymes work only in the presence of two other type of compounds, cofactors (such as zinc or iron) and coenzymes (such as vitamins). Other compounds inhibit enzyme function by either blocking the active site (competitive inhibitor) or bonding to the enzyme and changing its shape (noncompetitive inhibitor).
Enzymes are often referred to as catalysts because they increase efficiency in chemical reactions without being affected. Because of enzymes, cells can manage millions of chemical reactions per second without breaking a sweat. Because of enzymes, cells can harvest energy and raw materials from the food you eat to build a better you.
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