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Nutrition Science and Everyday Application - beta v 0.1

Nutrition Science and Everyday Application - beta v 0.1

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DIGESTION AND ABSORPTION OF LIPIDS 281<br />

directly absorbed into the bloodstream, but larger lipids such as long-chain fatty acids,<br />

monoglycerides, fat-soluble vitamins, <strong>and</strong> cholesterol need help with absorption <strong>and</strong><br />

transport to the bloodstream. Long-chain fatty acids <strong>and</strong> monoglycerides reassemble into<br />

triglycerides within the intestinal cell, <strong>and</strong> along with cholesterol <strong>and</strong> fat-soluble vitamins,<br />

are then incorporated into transport vehicles called chylomicrons. Chylomicrons are large<br />

structures with a core of triglycerides <strong>and</strong> cholesterol <strong>and</strong> an outer membrane made up<br />

of phospholipids, interspersed with proteins (called apolipoproteins) <strong>and</strong> cholesterol. This<br />

outer membrane makes them water-soluble so that they can travel in the aqueous<br />

environment of the body. Chylomicrons from the small intestine travel first into lymph<br />

vessels, which then deliver them to the bloodstream.<br />

Chylomicrons are one type of lipoprotein—transport vehicles for lipids in blood <strong>and</strong><br />

lymph. We’ll learn more about other types of lipoproteins on the next page.<br />

Figure 5.23. Structure of a chylomicron. Cholesterol is not shown in this figure, but chylomicrons<br />

contain cholesterol in both the lipid core <strong>and</strong> embedded on the surface of the structure.<br />

VIDEO: “Lipids—Digestion <strong>and</strong> Absorption,” by Alice Callahan, YouTube (November, 17, 2019), 8:49<br />

minutes.

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