Glycerophospholipids Glycerophospholipids are The most abundant lipids in cell membranes. Composed of glycerol, two fatty acids, phosphate and an amino alcohol. Fatty acid Glycerol Fatty acid PO4 Amino alcohol

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

Structure and Polarity of A Glycerophospholipid Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Lecithin and Cephalin Lecithin and cephalin are glycerophospholipids Abundant in brain and nerve tissues. Found in egg yolk, wheat germ, and yeast. Copyright © 2007 by Pearson Education, Inc Publishing as Benjamin Cummings

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. fatty acid sphingosine PO4 amino alcohol

Sphingosine Sphingosine is a long-chain unsaturated amino alcohol. CH3−(CH2)12 −CH=CH−CH−OH │ CH−NH2 CH2−OH sphingosine

Sphingolipids In sphingomyelin, a sphingolipid found in nerve cells There is an amide bond between a fatty acid and sphingosine, an 18-carbon alcohol. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Glycosphingolipids Glycosphingolipids contain monosaccharides bonded to the –OH of sphingosine by a glycosidic bond. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Glycosphingolipids (Cerebrosides) Are sphingolipids that contain monosaccharides. Can be a cerebroside with galactose. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Glycosphingolipids (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.

Gangliosides GM2 is a ganglioside That accumulates in Tay-Sachs disease. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Lipid Diseases (Lipidoses) In many lipid diseases, the deficiency of an enzyme causes the accumulation of glycolipids. TABLE 17.3 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Steroid Nucleus A steroid nucleus consists of 3 cyclohexane rings. 1 cyclopentane ring. No fatty acids. steroid nucleus

Cholesterol Cholesterol Is the most abundant steroid in the body. Has methyl CH3- groups, alkyl chain, and -OH attached to the steroid nucleus.

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

Cholesterol in Foods Cholesterol is Considered elevated if plasma cholesterol exceeds 200 mg/dL. TABLE 17.4 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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.

Bile Salts Polar region Nonpolar region

Lipoproteins Lipoproteins Combine lipids with proteins and phospholipids. Are soluble in water because the surface consists of polar lipids. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Types of Lipoproteins Lipoproteins Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs). TABLE 17.5 Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Transport of Lipoproteins in the Body Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

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

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.

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

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

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.

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.

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

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.

Transport Pathways Through Cell Membranes Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings