1 Glycerophospholipids are The most abundant lipids in cell membranes. Composed of glycerol, two...

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Glycerophospholipids are The most abundant lipids in cell membranes. Composed of glycerol, two fatty acids, phosphate

and an amino alcohol.

Glycerol

PO4Amino alcohol

Glycerophospholipids

Fatty acid

Fatty acid

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Glycerophospholipids Are Polar

A glycerophospholipid has Two nonpolar fatty acid chains. A phosphate group and a polar amino alcohol. CH3

│+ +

HO−CH2−CH2−N−CH3 HO−CH2−CH2−NH3

│ choline CH3 ethanolamine +

NH3

│ Amino alcohols HO−CH2−CH−COO−

serine

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Structure and Polarity of A Glycerophospholipid

Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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Lecithin and cephalin are glycerophospholipids Abundant in brain and nerve tissues. Found in egg yolk, wheat germ, and yeast.

Lecithin and Cephalin

Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

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Sphingolipids

Sphingolipids Are similar to phospholipids. Contain sphingosine (a long-chain amino alcohol), a

fatty acid, phosphate, and a small amino alcohol. Have polar and nonpolar regions.

sphingosine

PO4amino alcohol

fatty acid

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Sphingosine

Sphingosine is a long-chain unsaturated amino alcohol.

CH3−(CH2)12 −CH=CH−CH−OH

│

CH−NH2

│

CH2−OH

sphingosine

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In sphingomyelin, a sphingolipid found in nerve cells There is an amide bond between a fatty acid and

sphingosine, an 18-carbon alcohol.

Sphingolipids


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Glycosphingolipids

Glycosphingolipids contain monosaccharides bonded to the –OH of sphingosine by a glycosidic bond.


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Glycosphingolipids (Cerebrosides)

Glycosphingolipids Are sphingolipids that contain

monosaccharides. Can be a cerebroside with galactose.


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Glycosphingolipids (Gangliosides)

Gangliosides Are similar to cerebrosides, but contain two or

more monosaccharides. Are important in neurons. Act as receptor for hormones and viruses. Can accumulate and cause genetic diseases.

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Gangliosides

GM2 is a ganglioside

That accumulates in Tay-Sachs disease.


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Lipid Diseases (Lipidoses)

In many lipid diseases, the deficiency of an enzyme causes the accumulation of glycolipids.


TABLE 17.3

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Steroid Nucleus

A steroid nucleus consists of

3 cyclohexane rings.

1 cyclopentane ring.

No fatty acids.

steroid nucleus

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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

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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.

Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings

An artery clogged by cholesterol plaque

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Cholesterol in Foods

Cholesterol is

Considered elevated if plasma cholesterol exceeds 200 mg/dL.

TABLE 17.4


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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.

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Bile Salts

OH

COO- Na+CH2

H

N

O

COHCH3

CH3

HO

CH3

glycine, an amino acid cholic acid, a bile acid

sodium glycocholate, a bile salt

Nonpolar region

Polar region

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Lipoproteins

Lipoproteins• Combine lipids with proteins and phospholipids.• Are soluble in water because the surface consists of

polar lipids.


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Types of Lipoproteins

Lipoproteins Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high-density

lipoprotein (HDLs).

TABLE 17.5


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Transport of Lipoproteins in the Body


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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.


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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.

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Adrenal Corticosteroids


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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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Cell Membranes

Cell membranes Separate cellular contents from the external

environment. Consist of a lipid bilayer made of two rows of

phospholipids. Have an inner portion made of the nonpolar tails of

phospholipids with the polar heads at the outer and inner surfaces.

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Fluid Mosaic Model of Cell Membranes

The lipid bilayer Contains proteins, carbohydrates, and

cholesterol. Has unsaturated fatty acids that make cell

membranes fluid-like rather than rigid. Has proteins and carbohydrates on the surface

that communicate with hormones and neurotransmitters.

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Transport Through Cell Membranes

The transport of substances through cell

Membranes involves

Diffusion (passive transport), which moves particles from a higher to a lower concentration.

Facilitated transport, which uses protein channels to increase the rate of diffusion.

Active transport, which moves ions against a concentration gradient.

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Transport Pathways Through Cell Membranes


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