Lipids

“Fat, what good is it?”

Lipids

• Biomolecules soluble in organic solvents

• Roles– Nutritional– Structural– regulatory

Types of Lipids

• Glycerol-based

• Sphingolipids

• Steroids

• Eicosanoids/leukotrienes

Storage Lipids

• Fatty acids – Saturated and Unsaturated

• Relationship to melting point

• Triacylglycerides– Glycerol + 3 fatty acids

• Waxes

Glycerol based fats

CH2

CH

CH2 OH

OH

OH

• Glycerol on the left• Esterifies to 3 fatty

acids

Triacylglyerides

• Glycerol in blue• Fatty acids in red• Condensation

produces 3 water molecules

• Very nonpolar…excludes water

Lipids in Membranes:

• Phospholipids

• Cholesterol

• Glycolipds: Sugar group attached

• Proteins: either integral or peripheral

• Sphingolipids

Phosphoacylglycerols

• Glycerol esterified to 2 fatty acids.

• Third position is phosphate

• Other end of phosphate can combine with other molecules to form various derivatives

• amphipathic

Phosphoacylglycerols

CH2

CH

CH2 O

O

O

R1

O

O

R2

PO

O

O

X

Derivatives of Phosphoacylglycerols (PAG)

CH2

CH

CH2 O

O

O

R1

O

O

R2

PO

O

O

X

X- structure Name PAG name

H hydrogen Phosphatidic acid

serine Phosphatidyl serine

choline Phosphatidyl choline (lecithin)

ethanolamine Phosphatidyl ethanolamie

inositol Phosphatidyl inositol

H3N+ OH

O

O

OH

CH3N+

CH3

CH3

OHH3N+

H

OH

OH

H H

OH

H

OH

OH

HOH

H

Phosphatidyl choline with fatty acids as oleate and palmitate

O

CH3N+CH3

CH3

O

(CH2)14 CH3O

O

O

(CH2)7 CH

CH

(CH2)7 CH3

CH2

CH

CH2

OP

O

O

Sphingolipids

• Sphingosine instead of glycerol• Derivatized at ester C1• Fatty acids added at amine• Different types are found in plasma

membrane and myelin sheaths• Gangliosides

– cell to cell interactions– antigenic

Sphingosine

OH CH

CH

CH

(CH2)12-CH3

CH NH2

CH2OH

Sphingolipids

OH CH

CH

CH

(CH2)12-CH3

CH NH

CH2

R

O

OX

X name

H ceramide

monosaccharide cerebroside

carbohydrate ganglioside

sphingomyelinO

CH3N+CH3

CH3

P O

O

O

Sphingophospholipid with choline and the fatty acid as linolenic

O

(CH2)7 CH CH CH2CH CH CH2 CH CHCH2CH3NH

CH3N+CH3

CH3

O

OH CH

CH

CH

(CH2)12-CH3

CH

CH2OP

O

O

Cholesterol

OH

Role of Cholesterol

• Keeps the lipids in membrane from aggregrating: Keeps the membrane intact as a bilayer

• Precursor to Bile Acids– Act as detergentsto dissolve dietary fats

– Fats can be broken better by enzymes

• Precursor to steroid hormones that regulate gene expression

• Precursor to Vitamin D

Good vs. Bad Cholesterol

• Related to lipoproteins (protein + lipid complexes)

• Dietary excess fat is packaged into VLDL

• Fat cells (adipose cells) take these up convert to fatty acids

• Some VLDL is converted to LDL

• LDL is very rich in Cholesterol

LDL

• Too much LDL can circulate in the blood

• Build up in arteries; lead to heart attack

HDL

• Another lipoprotein that converts cholesterol into a lipoprotein that returns to the liver ; Removes cholesterol out of the bloodstream;

• believed to prevent heart attacks

Ratio of LDL to HDL

• LDL cholesterol of less than 100 mg/dL is the optimal level. Less than 130 mg/dL is near optimal for most people.

• A high LDL level (more than 160 mg/dL or 130 mg/dL or above if you have two or more risk factors for cardiovascular disease) reflects an increased risk of heart disease

• Low HDL cholesterol levels [less than 40 mg/dL] is thought to increase the risk for heart disease.

Steroid hormones

Eicosanoids• Prostaglandins: different types

– Some stimulate contraction of smooth muscle during menstruation and labor

– Others produce fever and inflammation and pain

• Thromboxanes: act in the formation of blood clot

• Leukotrienes: induces contraction of the muscle lining the lungs– overproduction leads to asthma

Eicosanoids/Leukotrienes