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3.6: Hydrolysis

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3.6: Hydrolysis


Hydrolysis is a chemical reaction in which water breaks a bond within a molecule. For example, it breaks peptides into amino acids, carbohydrates into simple sugars and DNA into nucleotides. Enzymes often facilitate these processes.

Hydrolysis Reverses Dehydration Synthesis

To break down complex carbohydrates, the linkage between individual sugar units needs to be broken. The reaction that breaks a glycosidic bond is called hydrolysis, as water is added to the compound. The glycosidic bonds between sugar molecules are stable, so hydrolases often catalyze hydrolysis. Hydrolases are enzymes that are specialized in catalyzing hydrolysis.

Different types of glycosidic bonds (e.g., 1-4 linkage, 1-6 linkage) require different hydrolases. The type of enzyme needed also depends on the location of the sugar unit within the polymer. For instance, starch primarily consists of 1-4 linked glucose, with a relatively small number of 1-6 glycosidic bonds. While α-amylase can cleave 1-4 glycosidic bonds in the middle of the polymer, the enzyme amyloglucosidase breaks only 1-6 or 1-4 bonds at the terminus (i.e., the last glucose unit at the end of the chain).

The Lack of Lactase Can Cause Gastrointestinal Symptoms

Human babies produce the enzyme lactase, which catalyzes the hydrolysis of milk sugar, or lactose. Lactose is a disaccharide that consists of glucose and galactose. In many areas of the world, humans stop producing lactase when they reach adulthood, leaving them lactose intolerant. The inability or reduced ability to hydrolyze lactose means that lactose passes through the intestine into the colon without being broken down into glucose and galactose. Some bacteria in the colon can metabolize lactose. The byproducts of this bacterial activity are gas and water influx into the colon, which causes gastrointestinal symptoms such as bloating, flatulence and diarrhea. These symptoms can be mitigated by either consuming lactase with any meal that contains dairy products or removing dairy from the diet altogether.

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