Hydrophobic interactions refer to the tendency of nonpolar substances to avoid contact with water. In biological systems, this phenomenon is crucial for the formation of cell membranes and protein structures. Nonpolar molecules cluster together in aqueous environments, minimizing their exposure to water, which helps stabilize the overall structure of cells and proteins. These interactions arise because water molecules form hydrogen bonds with each other, creating a structured network. When nonpolar molecules are present, they disrupt this network, leading to an increase in free energy. To reduce this disruption, nonpolar molecules aggregate, resulting in a more energetically favorable arrangement in the presence of water.