Download Phospholipids and Steroids

Lipids
Phospholipids
Steroids and Cholesterol
Plasma (Cell)Membranes
1
Phosphoglycerides
• Most abundant lipids in cell membranes
• Control cell permeability
FATTY ACID
FATTY ACID
glycerol
PO4
Amino
alcohol
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Lecithin
• Abundant in brain and nerve tissues
• Found in egg yolk, what germ, yeast
O
CH2 O C (CH2)14CH3
O
CH O
CH2
C
O
(CH2)14CH3
+
O P O CH2CH2N(CH3)3
-
O
choline, an amino alcohol
3
Sphingolipids
Esters of an 18-carbon alcohol sphingosine
FATTY ACID
sphingosine
PO4
Amino
alcohol
4
Sphingomyelin
Found in the myelin sheath
CH3(CH2)12CH=CH –CH–OH
sphingosine
O
‖
fatty acid
CH–NH –C –(CH2)14CH3
O
‖
+
CH2 –O –P –O –CH2CH2 –N–(CH3)3
‖
O–
choline
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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
9
Example of a Bile Salt
cholic acid, a bile acid
CH3
OH
CH3
CH3
HO
O
C N CH2 COO- Na+
H
gycine, an amino acid
OH
sodium glycocholate, a bile salt
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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
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Sex Hormones
CH3 OH
CH3
O
CH3 OH
CH3
HO
t e st ost e r on e
e st r ad iol
12
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
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Diagram of a Plasma
Membrane
Polar sections
Nonpolar tails
14
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
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Learning Check PL1
Identify each lipid as:
A.
B.
C.
D.
E.
F.
G.
(1) phospholipid
(3) triglyceride
(2) steroid
(4) sphingolipid
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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