A Level Biology Practice Exam

What kind of reaction is hydrolysis?

1. A reaction that releases energy

2. A breakdown reaction requiring water

3. A synthesis reaction

4. A reaction that does not involve water

The correct answer is: A breakdown reaction requiring water

Hydrolysis is indeed a breakdown reaction that specifically requires water. In this process, large molecules, such as polysaccharides, proteins, or lipids, are broken down into smaller units, like monosaccharides, amino acids, or fatty acids, by the addition of water. The water molecules are split into hydrogen and hydroxyl components, which then attach to the products of the reaction, thus facilitating the breakdown. This characteristic distinguishes hydrolysis from other types of reactions. For instance, it does not release energy in the same sense as catabolic reactions where energy may be freed, as hydrolysis primarily focuses on the cleavage of bonds in the presence of water. It is also not a synthesis reaction since it breaks down substances rather than building them up. Additionally, it cannot be categorized as a reaction that does not involve water, as water is a crucial component that drives the hydrolysis process.