Which of the following describes a tiny sphere of liquid that can transport drugs in the body?

A liposome is a tiny sphere of liquid composed of lipid bilayers that can encapsulate drugs, providing a means for transporting them through the body. These structures are particularly effective for drug delivery because they can encapsulate both hydrophilic (water-soluble) and hydrophobic (fat-soluble) substances, which expands the range of drugs that can be effectively delivered.

Liposomes enhance the bioavailability of drugs by protecting them from degradation in the bloodstream and facilitating their uptake by cells. They can also be engineered to release their contents at specific sites within the body, which is crucial for targeted therapy.

In contrast, micelles are formed from surfactants when they aggregate in solution and primarily serve to solubilize hydrophobic substances rather than acting as a drug delivery system. Vesicles are a more general term and can encapsulate materials, but liposomes are a specific type of vesicle designed for drug delivery. Emulsions consist of mixtures of oil and water, typically used in food and cosmetics rather than for targeted drug transport within the body. Thus, the defining characteristics and the application of liposomes make them the correct choice for describing a tiny sphere of liquid that transports drugs.