Lipids

1
Lipids

• Phospholipids
• Steroids and Cholesterol
• Plasma (Cell)Membranes

2
Phosphoglycerides

• Most abundant lipids in cell membranes
• Control cell permeability
• FATTY ACID
• FATTY ACID

glycerol
PO4
Amino alcohol
3
Lecithin

• Abundant in brain and nerve tissues
• Found in egg yolk, what germ, yeast

4
Sphingolipids

• Esters of an 18-carbon alcohol sphingosine
• FATTY ACID

sphingosine
PO4
Amino alcohol
5
Sphingomyelin

• Found in the myelin sheath
• CH3(CH2)12CHCH CHOH
• O
• sphingosine ? fatty acid
• CHNH 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

7
Cholesterol

• Most abundant steroid in the body
• Add methyl CH3- groups, alkyl chain, and -OH to
  steroid nucleus

8
Cholesterol in the Body

• Cellular membranes
• Myelin sheath, brain, and nerve tissue
• Bile salts
• Hormones
• Vitamin D

9
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
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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

12
Sex Hormones
13
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

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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

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Learning Check PL1

• Identify each lipid as (1) phospholipid (2)
  steroid
• (3) triglyceride (4) sphingolipid
• A. 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. 2 steroid
• B. phospholipid
• C. 3 triglyceride
• D. 4 sphingolipid
• E. 2 steroid
• F. 2 steroid
• G. 1 phospholipid