Nutrition Science and Everyday Application - beta v 0.1

Lipid Transport, Storage, and Utilization
Once dietary lipids are digested in the gastrointestinal tract and absorbed from the small
intestine, they need to be transported around the body so they can be utilized by cells or
stored for later use. Once again, the fact that lipids aren’t water-soluble means that they
need some help getting around the watery environment of the body. Let’s take a look at how
this works.
LIPOPROTEINS TRANSPORT LIPIDS AROUND THE BODY
Lipoproteins are transport vehicles for moving water-insoluble lipids around the body. There
are different types of lipoproteins that do different jobs. However, all are made up of the
same four basic components: cholesterol, triglycerides, phospholipids, and proteins.
The interior of a lipoprotein—called the lipid core—carries the triglycerides and
cholesterol esters, both of which are insoluble in water. Cholesterol esters are cholesterol
molecules with a fatty acid attached. The exterior of lipoproteins—called the surface coat—is
made up of components that are at least partially soluble in water: proteins (called
apolipoproteins), phospholipids, and unesterified cholesterol. The phospholipids are oriented
so that their water-soluble heads are pointed to the exterior, and their fat-soluble tails
are pointed towards the interior of the lipoprotein. Apoliproteins are similarly amphipathic
(soluble in both fat and water), a property that makes them useful for aiding in the transport
of lipids in the blood.
Figure 5.24. Basic structure of all lipoproteins. Note the orientation of phospholipids on the
surface coat.
While all lipoproteins have this same basic structure and contain the same four
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