Most enzymes are specific, which means they take part in a single chemical reaction within the cell. The enzyme, acetylcholinesterase, promotes a chemical reaction involved in the conduction of impulses trough the nerves. The end products of this enzymatic reaction are compounds acetate and choline. Digestive enzymes pepsin and chymotrypsin can take part in more than one enzymatic reaction. These enzymes are found in the digestive system and can break almost any protein, producing smaller units called amino acids as end products. A single mammalian cell contains about 3,000 enzymes, according to the Encyclopaedia Britannica.
Enzymatic reactions occur in plants in various circumstances, from the production of food through photosynthesis to the formation of cell walls and the defense against pathogens. The isoflavonoid-synthesis enzyme helps plants resist infections by modifying the structure of cell walls and making them more resistant to pathogenic microorganisms. Glycoside hydrolases and transglycosidases are enzymes involved in numerous reactions, including the metabolism of carbohydrates found in plant tissues.
In microorganisms, such as bacteria, enzymatic reactions can vary according to environmental conditions. For instance, if bacteria can get the end product of a certain reaction from the surrounding environment, the specific enzymatic reaction does not occur. In many cases, this helps the microorganism conserve energy. However, microorganisms also have constitutive enzymes, which are involved in the formation of membranes and cells organelles. Reactions involving these enzymes occur independently of environmental conditions.
In addition to breaking down large molecules, such as fats and carbohydrates into smaller components and promoting the formation of complex molecules, enzymatic reactions are responsible for other functions. The absorption of nutrients in the intestine, the development of sexual cells, the mechanism of immune defense, the processes of respiration and sensory perception depend on specific enzymatic reactions.