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

PO4

Amino

alcohol

Glycerophospholipids

Fatty acid

Fatty acid

Phospholipids

PolarHead Glycerol Fatty Acid Tails

HydrophobicHydrophilic

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 LipoproteinsLipoproteins:

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

CH3OH

C

O

N

H

CH2COO- 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

Mic

elles

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

Lysosomes

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 membraneCell membrane

“Heads” of

phospholipid

“Tails” of

phospholipid

Fibrous proteinCarbohydrateGlycolipid

Glycoprotein

Extracellular sideof membrane

Cytoplasmic sideof membrane

Cholesterolmolecules

Globularprotein

Doublelayer of

Phospholipidmolecules

Hydrophobicfatty acid

“tail”

HydrophilicPhosphate

“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.