What occurs during hydrolysis?

The correct answer identifies hydrolysis as a chemical process in which a molecule is split or broken down by the addition of water. This reaction is significant in various biological and chemical contexts. For instance, during hydrolysis, bonds within the molecule, such as covalent bonds, are broken as water molecules provide the necessary hydrogen and hydroxyl ions to facilitate the cleavage of these bonds.

This process is essential in numerous biochemical reactions, including the breakdown of larger biomolecules like carbohydrates, proteins, and fats into their monomeric units (like sugars, amino acids, or fatty acids). Hydrolysis is not just limited to biological systems; it is also a fundamental concept in chemistry, particularly in understanding the reactivity of compounds.

The other answer choices describe different processes that do not accurately represent hydrolysis. Combining a molecule with heat does not involve water's participation in breaking bonds, nor does it reflect the specific nature of hydrolysis. Similarly, combining two molecules into one suggests a synthesis reaction rather than a decomposition, and a chemical reaction releasing gas pertains to a different type of reaction where gaseous products are formed, such as certain acid-base or combustion reactions.