Which process occurs when two molecules combine, releasing a water molecule?

The correct answer focuses on dehydration synthesis, a key biochemical process where two molecules bond together and a water molecule is released as a byproduct. This reaction is essential in the formation of larger biological macromolecules from smaller units. For example, when carbohydrates, proteins, or nucleic acids are synthesized, individual monomers such as monosaccharides, amino acids, or nucleotides come together through dehydration synthesis.

In this process, the hydroxyl (–OH) group from one molecule and a hydrogen atom (–H) from another molecule combine to form water (H2O), which is then released. This removal of water facilitates the formation of covalent bonds, linking the two molecules together, which is fundamental for building complex structures in biological systems.

Hydrolysis, on the other hand, is the reaction where water is used to break apart molecules, whereas fermentation and respiration involve metabolic processes that do not directly relate to the formation of molecules through the release of water.