What is the Critical Micelle Concentration (CMC)?

The Critical Micelle Concentration (CMC) refers to the specific concentration of surfactants, such as detergents, at which micelles begin to form in solution. Below this concentration, individual surfactant molecules exist primarily in a dissolved state, while above it, they aggregate to form micelles, which are spherical structures composed of aggregates of surfactant molecules. This transition is significant because it represents a crucial point at which the properties of the solution change, particularly in how it interacts with hydrophobic molecules.

Understanding the concept of CMC is vital in biochemical applications, especially when dealing with membrane proteins, solubilization, or drug delivery systems, where micelles can encapsulate hydrophobic substances, enhancing their solubility and bioavailability. The other options mentioned do not accurately define CMC: it is not related to temperature, protein solubility, or protein concentrations in micellar structures. The defining feature of CMC is its role in the formation of micelles, which is why the choice that states it is the concentration at which detergents form micelles is the correct answer.