General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc Steroids: Cholesterol, Bile Salts, and Steroid Hormones 1 Chapter 17 Lipids

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.2 Steroid Nucleus A steroid 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.3 Cholesterol  is the most abundant steroid in the body  has methyl CH 3 -groups, an alkyl chain, and —OH attached to the steroid nucleus

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.4 Cholesterol in the Body 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 A normal, open artery. An artery clogged by cholesterol plaque

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.5 Cholesterol in Foods Cholesterol is  synthesized in the liver  obtained from foods  considered elevated if plasma cholesterol exceeds 200 mg/dL

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.6 Learning Check Match the components of the cholesterol molecule with each of the following: ___ alkyl chain___ hydroxyl group ___ steroid nucleus___ methyl group A C B D

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.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 A C B D

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.9 Sodium Glycocholate, a Bile Salt Nonpolar region Polar region

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.10 Lipoproteins  combine lipids with proteins and phospholipids  are soluble in water because the surface consists of polar lipids

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.11 Types of Lipoproteins Lipoproteins  differ in density, composition, and function  include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.12 Transport of Lipoproteins in the Body

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.13 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.14 Steroid Hormones (continued)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.15 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.16 Adrenal Corticosteroids (continued)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.17 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.18 Learning Check Identify each as a 1) fatty acid2) 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

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Solution A. Cholesterol2) steroid B. Glycerol, 2 fatty acids,4) phospholipid phosphate, and choline C. Glyceryl tristearate3) 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 19