How is cholesterol transported in the bloodstream?

Cholesterol is transported in the bloodstream attached to proteins known as lipoproteins. This is crucial because cholesterol itself is not water-soluble and cannot move freely in the aqueous environment of the bloodstream.

Lipoproteins serve as carriers for cholesterol and other lipids, ensuring their transport to various tissues and organs. There are several types of lipoproteins, including low-density lipoproteins (LDL) and high-density lipoproteins (HDL), each playing different roles in lipid metabolism and transport. LDL is often referred to as "bad" cholesterol because it can contribute to plaque buildup in arteries, while HDL is known as "good" cholesterol for its role in carrying cholesterol away from the arteries to the liver for excretion or recycling.

The other options do not accurately represent how cholesterol is transported. Enzymes are involved in the metabolism of lipids but do not directly transport cholesterol. Cholesterol cannot be transported in a water-soluble form due to its hydrophobic nature. Considering it as a solid compound does not apply because cholesterol exists primarily in a molecular form rather than as a solid substance within the bloodstream.