Compound and
Derived Lipids
Glycerophospholipids are:
The most abundant lipids in cell membranes.
Composed of glycerol, two fatty acids, phosphate and an amino alcohol.
Glycerol
PO
4 Aminoalcohol
Glycerophospholipids
Fatty acid Fatty acid
Phospholipids
Polar
Head Glycerol Fatty Acid Tails
Hydrophobic
Hydrophilic
Polarity of Glycerophospholipids
A glycerophospholipid has polar and nonpolar regions.
Lecithin and cephalin are glycerophospholipids:
Abundant in brain and nerve tissues.
Found in egg yolk, wheat germ, and yeast.
Lecithin and Cephalin
Sphingolipids are phospholipids that have an amide bond between a fatty acid and sphingosine, an 18- carbon alcohol.
Sphingolipids
Glycosphingolipids
Glycosphingolipids (cerebrosides and
gangliosides) contain monosaccharides
bonded to the –OH of sphingosine by a
glycosidic bond.
Cerebrosides contain only one
monosaccharide.
Gangliosides
Gangliosides are similar to cerebrosides, but contain two or more monosaccharides.
Lipid Diseases (Lipidoses)
In many lipid diseases, the deficiency of an enzyme causes the accumulation of glycolipids.
Steroids are:
Lipids containing the steroid nucleus, which is a fused structure of four rings.
Found in cholesterol, bile salts, hormones, and vitamin D.
Steroids
steroid nucleus
Complex ring forms
Some hormones
Cholesterol
Natural substance
Found in membranes
Gives membranes natural flexibility
Steroids
Steroids
Cholesterol Estradiol
Testosterone
The most abundant steroid in the body.
Contains 27 carbon atoms.
At C3 there is a –OH group; so it is an alcohol.
Composed of the steroid nucleus with methyl groups, an alkyl chain, and a hydroxyl group attached.
Precursor for adrenal corticosteroids, vitamin D and bile acids
Cholesterol
CH3
HO
CH3
CH3 CH3
CH3
Cholesterol in Foods
Cholesterol:
Is considered elevated if plasma cholesterol exceeds 200-220
mg/dL.
Is synthesized in the liver and obtained from foods.
100 g 1 100 g 100 g 100 g 100 g 100 g
1 tablespoon 1 cup
1 cup
1 tablespoon
Lipoproteins
Combine lipids with proteins and phospholipids.
Are soluble in water because the surface consists of polar lipids.
Types of Lipoproteins
Lipoproteins:
Differ in density, composition, and function.
Include low-density lipoprotein (LDLs) and high-density lipoprotein (HDLs).
Transport of Lipoproteins in the
Body
Bile Salts
Are synthesized from cholesterol and stored in the gall bladder.
Emulsify fats and oils to give a greater surface area for lipid digesting enzymes.
CH3
HO
CH3 CH3
OH C
O
N H
CH2
COO- Na+
OH
glycine, an amino acid cholic acid, a bile acid
sodium glycocholate, a bile salt
Steroid Hormones
Steroid hormones:
Are produced from cholesterol.
Include sex hormones such as androgens
(testosterone) in males and estrogens
(estradiol) in females
Estradiol
Testosterone
Adrenal Corticosteroids
Steroid hormones called adrenal corticosteroids:
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
Lipid Profile
Lipid profile includes:
1)Total lipids 2)Triglycerides 3) Cholesterol 4) HDL
5) LDL
These tests must be carried out after 12-15 hrs.
fasting due the high molecular weight of lipid
molecules and the prolonged digestion and
metabolism.
Phospholipids
Polar group
Phospholipid Bilayer
M ic e ll e s
A Composite Cell
Major parts include:
• Nucleus
• Cytoplasm
• Cell membrane
Microtubules
Flagellum
Nuclear envelope Basal body
Chromatin Ribosomes
Cell membrane
Mitochondrion
Cilia
Microtubules Microtubule
Centrioles
Microvilli
L ysosomes Nucleolus
Nucleus
Phospholipid bilayer
Smooth Endoplasmic
reticulum Rough Endoplasmic
reticulum
Golgi apparatus Secretory
vesicles
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.
Cell Membrane
Cell membrane Cell membrane
“Heads” of phospholipid
“Tails” of phospholipid
Fibrous protein Carbohydrate
Glycolipid
Glycoprotein Extracellular side
of membrane
Cytoplasmic side of membrane
Cholesterol molecules
Globular protein
Double layer of Phospholipid
molecules
Hydrophobic fatty acid
“tail”
Hydrophilic Phosphate
“head”
Fluid Mosaic Model of Cell Membranes
The lipid bilayer contains
proteins, carbohydrates, and cholesterol.
The unsaturated fatty acids make cell membranes fluid- like rather than rigid.
Proteins and carbohydrates on the outer surface
communicate with hormones and neurotransmitters.
Transport Through Cell Membranes
Diffusion (passive transport) moves particles from a higher to a lower concentration.
Facilitated transport uses protein channels to increase the rate of diffusion.
Active transport moves ions against a concentration
gradient.
