1. Steroids and Cholesterol Plasma (Cell)Membranes
Lipids
Phospholipids
Steroids and Cholesterol
Plasma (Cell)Membranes

2. Phosphoglycerides Most abundant lipids in cell membranes
Control cell permeability
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
PO4
Amino
alcohol

5. Sphingomyelin Found in the myelin sheath CH3(CH2)12CH=CH –CH–OH O
sphingosine ‖ fatty acid
CH–NH –C –(CH2)14CH3
‖ CH2 –O –P –O –CH2CH2 –N–(CH3)3 ‖
O– choline

6. Steroids Steroid nucleus 3 cyclohexane rings 1 cyclopentane ring

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

10. Example of a Bile Salt

11. 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

14. Diagram of a Plasma Membrane
Polar sections
Nonpolar tails

15. 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

16. 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

17. Solution PL1 A. 2 steroid B. phospholipid C. 3 triglyceride
D. 4 sphingolipid
E. 2 steroid
F. 2 steroid
G. 1 phospholipid