Final answer:
Cholesterol combines with phospholipids and proteins to form water-soluble particles called Lipoproteins for transport in the bloodstream. Different types of lipoproteins, such as chylomicrons and HDL, transport lipids through the body by varying in density and composition. The correct answer is D) Lipoproteins.
Step-by-step explanation:
In order for cholesterol to be transported from where it is synthesized to the tissues, it combines with phospholipids and proteins to form small water-soluble spherical particles called Lipoproteins. Cholesterol is insoluble in water and cannot be transported in the aqueous environment of the blood without being bound to these lipoproteins. There are different types of lipoproteins, including chylomicrons, High Density Lipoproteins (HDL), and others, which vary in their density and composition depending on their proportion of lipid and protein content.
Lipoproteins such as chylomicrons are formed within the intestinal cells after lipids are mixed with phospholipids and cholesterol and then coated with proteins. These chylomicrons are large particles that can transport triglycerides, cholesterol, and other lipids through the lymphatic system into the bloodstream. Once in the bloodstream, enzymes break down the lipids, allowing their constituents to be used by the body or stored. Thus, lipoproteins are essential for the transport of cholesterol and other lipids within a water-rich environment like blood.