Lipids
Phospholipids Steroids and Cholesterol Plasma (Cell)Membranes
1
Phosphoglycerides
• Most abundant lipids in cell membranes • Control cell permeability FATTY ACID
glycerol
FATTY ACID
PO4
Amino alcohol
2
Lecithin
• Abundant in brain and nerve tissues • Found in egg yolk, what germ, yeast
O CH2 CH O O C O C O (C H 2 ) 1 4 C H 3 (C H 2 ) 1 4 C H 3 O
-
CH2 O P O
+ C H 2 C H 2 N (C H 3 ) 3 c h o lin e , a n a m in o a lc o h o l
3
Sphingolipids
Esters of an 18-carbon alcohol sphingosine
FATTY ACID
sphingosine Amino alcohol
4
PO4
Sphingomyelin
Found in the myelin sheath
CH3(CH2)12CH=CH –CH–OH sphingosine
O ‖ O
fatty acid
CH–NH –C –(CH2)14CH3
‖ + CH2 –O –P –O –CH2CH2 –N–(CH3)3 ‖ O– choline 5
Steroids
• Steroid nucleus • 3 cyclohexane rings • 1 cyclopentane ring
steroid nucleus
6
Cholesterol
• Most abundant steroid in the body • Add methyl CH3- groups, alkyl chain, and OH to steroid nucleus
CH3 CH3 CH3 CH3 CH3
HO
7
Cholesterol in the Body
• Cellular membranes • Myelin sheath, brain, and nerve tissue • Bile salts • Hormones • Vitamin D
8
Bile Salts
• Synthesized in the liver from cholesterol • Stored in the gallbladder • Secreted into small intestine • Mix with fats to break them part
• Emsulsify fat particles
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Example of a Bile Salt
c h o lic a c id , a b ile a c id CH3 OH CH3 CH3 O C N H g y c in e , a n a m in o a c id CH2 C OO N a
+
HO
OH s o d iu m g ly c o c h o la te , a b ile s a lt
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Steroid Hormones
• Chemical messengers in cells • Sex hormones Androgens in males (testosterone) Estrogens in females (estradiol) • Adrenocorticosteroids from adrenal glands mineralocorticoids (electrolyte balance) glucocorticoids regulate glucose level
11
Sex Hormones
C H 3 OH CH3 CH3 C H 3 OH
O t e st o st e r o n e
HO e st r a d io l
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Plasma Membranes
• Surround cells • Lipid bilayer pf phospholipids
• Nonpolar hydrocarbon tails in center • Polar (hydrophilic) sections on outside • Some unsaturated fatty acids give flexibility
• Keep aqueous contents inside • Allow certain biochemicals to pass through
13
Diagram of a Plasma Membrane
Polar sections
Nonpolar tails
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Other Structures in Membranes
• Cholesterol molecules add strength • Glycolipids on surface communicate with other cells • Proteins embedded in bilayer move certain substances (water, K+, Cl-, HCO3-) across the cell membrane • Proteins on surface act as receptors for hormones and other biochemicals
15
Learning Check PL1
Identify each lipid as: (1) phospholipid (3) triglyceride (2) steroid (4) sphingolipid
A. B. C. D. E. F. G.
Cholesterol Glycerol, 2 fatty acids, phosphate, and choline Glyceryl tristearate Sphingosine, fatty acid, phosphate, and choline Estradiol Bile salts Most of plasma membranes
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Solution PL1
A. B. C. D. E. F. G. 2 steroid phospholipid 3 triglyceride 4 sphingolipid 2 steroid 2 steroid 1 phospholipid
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