Understanding Steroids and Lipid Metabolism in the Body

1. Chapter 17 Lipids 17.7Steroids: Cholesterol, Bile Salts, and Steroid Hormones

2. Steroid Nucleus Asteroid nucleus • has 3 cyclohexane rings • has 1 cyclopentane ring • contains no fatty acids • has four rings A, B, C, and D • is numbered from the carbon atoms in ring A to two methyl groups at 18 and 19

3. Cholesterol Cholesterol • is the most abundant steroid in the body • has methyl CH3-groups, an alkyl chain, and—OH attached to the steroid nucleus

4. Cholesterol in the Body A normal, open artery. Cholesterol in the body • is obtained from meats, milk, and eggs • is synthesized in the liver • is needed for cell membranes, brain and nerve tissue, steroid hormones, and vitamin D • clogs arteries when high levels form plaque An artery clogged by cholesterol plaque

5. Cholesterol in Foods Cholesterolis • synthesized in the liver • obtained from foods • considered elevated if plasma cholesterol exceeds 200 mg/dL

6. Learning Check Match the components of the cholesterol molecule with each of the following: ___ alkyl chain ___ hydroxyl group ___ steroid nucleus ___ methyl group D B A C

7. Solution Match the components of the cholesterol molecule with each of the following: D alkyl chain A hydroxyl group C steroid nucleus B methyl group D B A C

8. Bile Salts Bile salts • are synthesized in the liver from cholesterol • are stored in the gallbladder • are secreted into the small intestine • have a polar and a nonpolar region • mix with fats to break them part • emulsify fat particles to provide large surface area

9. Sodium Glycocholate, a Bile Salt Polar region Nonpolar region

10. Lipoproteins Lipoproteins • combine lipids with proteins and phospholipids • are soluble in water because the surface consists of polar lipids

11. Types of Lipoproteins Lipoproteins • differ in density, composition, and function • include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs)

12. Steroid Hormones Steroid hormones • are chemical messengers in cells • are produced from cholesterol • include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females

13. Steroid Hormones (continued)

14. Adrenal Corticosteroids Adrenal corticosteroids are steroid hormones that • are produced by the adrenal glands located on the top of each kidney • include aldosterone, which regulates electrolytes and water balance by the kidneys • include cortisone, a glucocorticoid, which increases blood glucose level and stimulates the synthesis of glycogen in the liver

15. Adrenal Corticosteroids (continued)

16. Anabolic Steroids Anabolic steroids • are derivatives of testosterone • are used illegally to increase muscle mass • have side effects that include fluid retention, hair growth, sleep disturbance, and liver damage

17. Learning Check Identify each as a 1) fatty acid 2) steroid 3) triacylglycerol 4) phospholipid 5) sphingolipid A. cholesterol B. glycerol, 2 fatty acids, phosphate, and choline C. glyceryl tristearate D. sphingosine, fatty acid, phosphate, and choline E. estradiol F. bile salts G. lipids in plasma membranes

18. Solution A. Cholesterol 2) steroid B. Glycerol, 2 fatty acids, 4) phospholipid phosphate, and choline C. Glyceryl tristearate 3) triacylglycerol D. Sphingosine, fatty acid, 5) sphingolipid phosphate, and choline E. Estradiol 2) steroid F. Bile salts 2) steroid G. Lipids in plasma 4) phospholipid, membranes 5) sphingolipid