A condensation reaction is a chemical process where two molecules combine to form a larger molecule, releasing a small molecule, often water. This type of reaction is common in organic chemistry and is essential for forming complex structures like polymers and biomolecules. In biological systems, condensation reactions are crucial for synthesizing macromolecules such as proteins, nucleic acids, and carbohydrates. For example, when amino acids link together to form a protein, a condensation reaction occurs, releasing water as a byproduct. This process helps build the diverse structures necessary for life.