Chapter 10- Lipids

Fatty Acids

carboyl group with 4-36 hydrocarbon chain

most have even # of carbons

unbrached

Fatty Acids Names

Lauric Acid- 12:0

Myristic Acid- 14:0

Palmitic Acid- 16:0

Stearic Acid- 18:0

Palmitoleic Acid- 16:1 Delta 9

Oleic Acid- 18:2 Delta 9,12

alpha-Linolenic Acid- 18:3 Delta 3,6,9

Omega Fatty Acids

Human Need them but cannot synthesize them

include:

• ALA- 18:3 w3

• DHA- 20:5 w3

• EPA- 22:6 w3

Solubilty and Melting Point

Solubility

• decreases as the chain length increases

Melting Point

• decreases as the chain length decreases

• decreases as the number of double bonds increases

Melting Points with Double Bonds

Saturated Fatty Acids Pack in fairly orderly way

• favorable interactions

Unsaturated Cis fatty acids pack less orderly due to the kinks

• less favorable interactions

It takes less thermal energy to disrupt disordered packing of unsaturated fatty acids

• unsaturated cis fatty acids have a lower melting points

Trans Fatty Acids

trans fatty acid form by partial dehydrogenation of unsaturated fatty acids

• done to increase shelf life or stability at high temps of oils used in cooking

A trans double bond allows a given fatty acis to adopt an extened conformation

Consuming trans fats increases risk of cardiovascular disease

• avoid deep frying partially hydrogenated vetable oils

• Current Trend: reduced trans fats foods

Triacylglycerols

The majority of fatty acids in biological systems

• solid ones are called fats

• lipids ones are called oils

The primary storage of lipids- body fats

Fats and Fuel Storage

Fatty acids carry more energy per carbon beasue they are more reduced

Carry less water per gram because they are nonpolar

glucose and glycogen are for short term energy needs and quick delivery

Fats are for long term energy needs, good storage, and slow delivery

Waxes

esters of long-chain saturated and unsaturated fatty acids with long-chain alcohol

insoluble and have melting points

variety of functions

Stuctural lipids in membranes

Contain polar head groups and nonpolar tails

Diversification can come from:

• different backbones

• changing fatty acids

• head groups

the properties of head groups determine the surface properties of membranes

different organisms have different membrane lipid head groups composition

different tissues have different membrane lipid head group compositions

Glycerophospholipids

primary constituents of cell membranes

two fatty acids from ester linkages with the first and second hydroxyl groups of L-glycerol-3-phospahte

the phosphate group is charged at cell pH

Phosphatidylcholine

is the major component of most eukaryotic cell membranes

many prokaryotes cannot synthesis this lipid their membranes do not contain this

Ether Lipids

vertebrate heart tissue

also found in some protozoa and anaerobic bacteria

function is not well understood

Sphingolipids

the backbone is not glycerol- is long chain amino alcohol sphingosine

fatty acid is joined via amide linages

a polar head is connected by a glycosidic or phosphodiester linkage

foudn largely in outer face of plasma membrane

Glycosphingolipids

blood groups are determined by the sugars on the head groups

structure of sugar is determined by an expression of specific glycosyltransferases

• no glycosyltransferases = O type

• N-acetylgalactosamine = A type

• Galactose = B type

Sterol

4 Four fused rings

hydroxyl group in the A-ring

almost planar

Cholesterol

are present in the membrane of mots eukaryotic cells

• moderate fluidity and permeability

• thicken the plasma membrane

• no steril in most bacteria

Mammals obtain cholesterol from food or synthesiza it de novo in the liver

Binds to protiens and is transported to tissues in the blood vessels- in LDL can clog arteries

Mant hormones are derived of sterols

Steroid Hormones

Sertoids are oxidized derivatives of sterols

have sterol nucleus but lack the alkyl chain found in cholesterol

Biologically Active Lipids

Lipid-Soluble vitamins ( A D E and K)

signaling molecules between nearby cells

Signaling Lipids

Enzymatic oxidation of arachidonic acid yield

• prostaglandins- inflammation and fever

• thromboxanes- formation of blood cells

• leukotrienes- smooth muscle contraction in lungs

Vitamin D

Synthesized from cholesterol and regulates calcium metabolism

Synthesized by UV light

Vitamin A (Retinol)

Derived from Beta-Carotene

Involved in visual pigment

Precursor for other hormone involved in signaling

Vitamin E

An Antioxidant

Vitamin K

A blood clotting cofactor

Warfarin

A blood anticoagulant

Polyketides

are a deverse family of compounds synthesized similarly to fatty acid biosynthesis

• commonly secondary metabolities with specialized function

  • Erythromycin- antibiotics

  • Amphotericin B- Antifungal

  • Lovastatin- Statin (mimics cholesterol to prevent cholesterol making)