1. LIPIDS III

2. STEROLS Cholesterol Male & female sex hormones Bile acids Vitamin D
Adrenal corticosteroids

3. Sterols Compounds with multi-ring structure Insoluble in water
Present both in plant and animal foods
Major sterol is cholesterol
However, cholesterol is found only in animal products (manufactured in liver)
High content in organ meats and egg yolk

4. Structure of steroid hormones:

5. Common Sterol Compounds
Vitamin D3 (cholecalciferol)

6. Bile acids (bile salts) are polar derivatives of cholesterol, formed in liver and secreted into the gall bladder.
They pass via the bile duct into the intestine, where they aid digestion of fats & fat-soluble vitamins.
Bile acids are amphipathic, with detergent properties.
Bile acids emulsify fat globules into smaller micelles, increasing the surface area accessible to lipid-hydrolyzing enzymes.
They also help to solubilize lipid breakdown products (e.g., mono- & diacylglycerols from triacylglycerol hydrolysis).

7. Lipoproteins Molecular complexes found in blood plasma Contain:
Neutral lipid core of cholesterol esters and/or TAGs
Surrounded by a layer of:
Phospholopid
Cholesterol
Protein
Classes:
Chylomicrons, VLDL, LDL, HDL

8. Model Structure of a Plasma Lipoprotein

9. Major Classes of Lipoproteins
Chylomicrons:
Very large and very low density
Transport intestineadipose
VLDL:
Made in liver
Transport lipids to tissues
LDL: carry cholesterol to tissues
HDL:
Scavenge excess cholesterol esters
“Good cholesterol”

10. C P T
100% T P C C P T C P T
80%
60%
Composition
40%
20% 0%
Chylo-
microns
VLDL
LDL
HDL
Lipoprotein Type
The major classes of lipoproteins and their relative content of triacylglycerol (T),cholesterol (C) and protein (P).

11. Relative Composition of Lipoproteins

12. Lipid peroxidation a non-enzymatic reaction catalyzed by oxygen
may occur in tissues or in foods (spoilage)
the hydroperoxide formed is very reactive and leads to the formation of free radicals which oxidize protein and/or DNA (causes aging and cancer)
principle is also used in drying oils (linseed, tung, walnut) to form hard films

13. Learning Check PL1
Identify each lipid as: (1) phospholipid (2) steroid
(3) triglyceride (4) sphingolipid
A. Cholesterol
Glycerol, 2 fatty acids, phosphate, and choline
Glyceryl tristearate
Sphingosine, fatty acid, phosphate, and choline
Estradiol
Bile salts
Most of plasma membranes

14. Solution PL1 A. 2 steroid B. phospholipid C. 3 triglyceride
D. 4 sphingolipid
E. 2 steroid
F. 2 steroid
G. 1 phospholipid

15. ABDULLATIF TAHA ABDULLA Dep. Of BIOCHEMISTRY
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