1 Chapter 15 Lipids 15.6 Steroids: Cholesterol, and Steroid Hormones Copyright © 2005 by Pearson...

1

Chapter 15 Lipids

15.6 Steroids: Cholesterol, and Steroid

Hormones

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

CH3

CH3CH3

CH3

HO

CH3

2

Steroid Nucleus

A steroid nucleus consists of

• 3 cyclohexane rings.

• 1 cyclopentane ring.

• no fatty acids.

steroid nucleus

3

Cholesterol

Cholesterol• is the most abundant steroid in the body.

• has methyl CH3- groups, alkyl chain, and -OH attached to the steroid nucleus.

CH3

CH3CH3

CH3

HO

CH3

4

Cholesterol in the Body

Cholesterol • 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

A normal, open artery.

5

Cholesterol in Foods

Cholesterol• is considered

elevated if plasma cholesterol exceeds 200 mg/dL.

• is synthesized in the liver and obtained from foods.

6

Learning Check

Match the components of the cholesterol molecule with

the following:

___ carbon chain ___hydroxyl group

___ steroid nucleus ___methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D

7

Solution

Match the components of the cholesterol molecule with

the following:

_D carbon chain _A_hydroxyl group

_C steroid nucleus _B_methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D

8

Lipoproteins

Lipoproteins• combine lipids

with proteins and phospholipids.

• are soluble in water because the surface consists of polar lipids.

9

Types of Lipoproteins

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

lipoprotein (HDLs).

10

Transport of Lipoproteins in the Body

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Steroid Hormones

Steroid hormones are• chemical messengers in cells.• sex hormones.

Androgens in males (testosterone)

Estrogens in females (estradiol)• Adrenocortical hormones from adrenal glands.

mineralocorticoids (electrolyte balance)

glucocorticoids regulate glucose level

12

Steroid Hormones

Steroid hormones• are produced from

cholesterol.

• include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females.

13

Adrenal Corticosteroids

Steroid hormones called adrenal corticosteroids • 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.

14

Anabolic Steroids

Anabolic steroids• are derivatives of testosterone.• are used illegally to increase muscle mass.• have side effects including fluid retention, hair growth,

sleep disturbance, and liver damage.

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Adrenal Corticosteroids

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Learning Check

Identify each lipid as

(1) fatty acid (2) steroid (3) triacylglycerol.

A. Cholesterol

B. Stearic acid

C. Glyceryl tristearate

D. Estradiol

E. Contains no fatty acids.

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Solution

Identify each lipid as:

(1) fatty acid (2) steroid (3) triacylglycerol

A. 2 Cholesterol

B. 1 Stearic acid

C. 3 Glyceryl tristearate

D. 2 Estradiol

E. 2 Contains no fatty acids.

.