Hydrophobic substances are characterized by what property?

Hydrophobic substances are characterized by their repulsion from water. This property arises because hydrophobic molecules, often nonpolar, do not interact well with the polar molecules that make up water. As a result, these substances tend to aggregate in aqueous environments to minimize their exposure to water, often forming separate phases or layers.

This behavior is critical in biological systems, especially in the formation of cell membranes, where hydrophobic tails of phospholipids face inward away from water, creating a stable barrier that separates the internal environment of the cell from the external surroundings. Understanding the nature of hydrophobic interactions is essential in many biological processes, such as protein folding and the formation of lipid bilayers.

Other choices relate to properties that do not apply to hydrophobic substances: attraction and solubility in water indicate a tendency to interact with water, which does not align with the behavior of hydrophobic materials. Promotion of cellular activities does not directly describe a property of hydrophobic substances, though these properties can play a role in how cells function.