Chapter 17 Lipids

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

17.7Steroids: Cholesterol, Bile Salts, and

Steroid Hormones

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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


Cholesterol

Cholesterol is the most abundant steroid in the body has methyl CH3-groups, an alkyl chain, and

—OH attached to the steroid nucleus


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


Cholesterol in Foods

Cholesterol is synthesized in the liver obtained from foods considered elevated if

plasma cholesterol exceeds 200 mg/dL


Learning Check

Match the components of the cholesterol molecule witheach of the following:___ alkyl chain ___ hydroxyl group___ steroid nucleus ___ methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D


Solution

Match the components of the cholesterol molecule witheach of the following: D alkyl chain A hydroxyl group C steroid nucleus B methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D


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


Sodium Glycocholate, a Bile Salt

Nonpolar region

Polar region


Lipoproteins

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

polar lipids


Types of Lipoproteins

Lipoproteins differ in density, composition, and function include low-density lipoprotein (LDLs) and high-density

lipoprotein (HDLs)


Transport of Lipoproteins in the Body


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


Steroid Hormones (continued)


Adrenal Corticosteroids

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


Adrenal Corticosteroids (continued)


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


Learning Check

Identify each as a 1) fatty acid 2) steroid 3) triacylglycerol4) phospholipid 5) sphingolipid

A. cholesterolB. glycerol, 2 fatty acids, phosphate, and cholineC. glyceryl tristearateD. sphingosine, fatty acid, phosphate, and cholineE. estradiolF. bile saltsG. lipids in plasma membranes

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

Solution

A. Cholesterol 2) steroidB. Glycerol, 2 fatty acids, 4) phospholipid

phosphate, and cholineC. Glyceryl tristearate 3) triacylglycerol D. Sphingosine, fatty acid, 5) sphingolipid

phosphate, and cholineE. Estradiol 2) steroidF. Bile salts 2) steroidG. Lipids in plasma 4) phospholipid,

membranes 5) sphingolipid

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Chapter 17 Lipids