Lipids

• Store Energy in a Fat Cell

• Part of membranes

• Serve as chemical messengers

Energy Storage

• Humans store Energy in the form of fats

• Some Energy storage is in the form of the carbohydrate glycogen – fast energy

• Fats produce 50% more energy per gram than carbohydrates

• 9 kcal/gram compared to 4 kcal/gram

Membrane Components

• Because lipids are insoluble in water, they work well as membranes to separate compartments in the body

• The structure of lipids makes them water repellent or hydrophobic

Messengers

• Primary messengers like steroids

• Secondary messengers like prostaglandins or thromboxanes

Classification of Lipids

• Classified into four groups

1) Fats and waxes

2) Complex Lipids

3) Steroids

4) Prostaglandins

Structure of Fats

• Fats are esters• Alcohol part is always

glycerol

• Acid part varies but is a “Fatty Acid”

glycerolH2C

HC

H2C

OH

OH

OH

palmitic acid

CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3 OH

O

a typical “fatty acid”

also called “glycerin”

Structure of Fats• Fatty Acids (FA)

1) Practically all straight chain with no branches

2) 10 to 20 C in length

3) Contain an even number of C

The body builds FA from two carbon units

of acetic acid (acetate ion)

4) Those with double bonds are usually in the cis isomer formation

palmitic acid

CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH3 OH

O

Structure of Fats

• Fatty Acids + Glycerol = FAT (an ester)

C (CH2)16 CH3

O

HC

H2C

H2C C (CH2)12 CH3O

O

O

O C (CH2)16 CH3

O

C (CH2)16 CH3

O

HC

H2C

H2C C (CH2)12 CH3O

O

O

O C (CH2)16 CH3

O

glycerol

first FA

second FA

third FA

Structure of Fats

• FATS– Triglycerides (three FA esterified with

glycerol)• Also called Triacylglycerides

– diglycerides (two FA esterified w/ glycerol)– Monoglycerides (one FA esterified w/

glycerol)– Fats are insoluble in water– Exist as both saturated and unsaturated FA

Structure of Fats• FATS

– Saturated Fatty Acids• Fit together well - close, parallel alignment• Regular pattern

– Unsaturated Fatty Acids• cis/trans double bonds do not allow regular

packing• LOWER mp and bp lower than the Sat’d. FA

Properties of Fats

• Physical State - FATS– Animal fats

• generally solids at RT• contain mostly saturated FA

– Plant and Fish oils• generally liquids at RT• contain more unsaturated FA

Properties of Fats

• PURE Fats – Colorless, odorless, and tasteless– Tastes, odors, colors are caused

by substances dissolved in the fats

From Yahoo Images

Hydrogenation

• Treatment with hydrogen gas, H2

• Catalyst required

• NOT difficult to convert unsaturated FA to saturated FA

• Called “hardening”

• Margarine contains more unsaturation than hydrogenated shortenings– Crisco, Spry, etc.

Hydrogenation

• Unsaturated converted to saturated:

HC

H2C

H2C C (CH2)12 CH3O

O

O

O

C (CH2)6 CH2

CH CH

CH2 (CH2)6 CH3

O

C (CH2)6 CH2

CH CH

CH2 (CH2)6 CH3

O

+ H2

catalyst

HC

H2C

H2C C (CH2)12 CH3O

O

O

O

C (CH2)6 CH2

CH2 CH2

CH2 (CH2)6 CH3

O

C (CH2)6 CH2

CH2 CH2

CH2 (CH2)6 CH3

O

Saponification• Triglycerides are subject to hydrolysis

– Can be hydrolyzed with acid or base– Base hydrolysis is called “saponification”– Result of base hydrolysis is a SOAP

• SOAP– The mixture of sodium salts of Fatty Acids

produced by saponification is called SOAP.

Saponification

• Triglycerides are subject to hydrolysis– base hydrolysis is called “saponification”

HC

H2C

H2C C (CH2)12 CH3O

O

O

O

C (CH2)6 CH2

CH CH

CH2 (CH2)6 CH3

O

C (CH2)6 CH2

CH CH

CH2 (CH2)6 CH3

O

+ 3 NaOHH2O

H2C

HC

H2C

OH

OH

OHC (CH2)12 CH3O

O

Na+ -

+

O C (CH2)6 CH2

CH CH

CH2 (CH2)6 CH3

O

Na+ -2

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• Pre-18th century soap making… It is said of Queen Elizabeth I that she bathed once a month, "whether she needed to or not". Whether she used soap is not recorded. But soap was a commodity only available to the wealthy before modern times.

• Source of “lye”… A large wooden hopper, which was large at the top and tapered down to a small bottom, was kept in the backyard near the kitchen door. The hopper was made of clapboards, which were arranged as a pyramid turned up side down. Dried grass or cornhusks were put into the bottom of the container to act as a strainer. In this the wood ashes from the hearth were stored. When the hopper was filled, many buckets of water had to be drawn from the well and poured over the ashes. Through a trough from the bottom of the hopper came the drops of strong brown lye, which was put in a large kettle over the fire to boil. As soon as the lye would float an egg, scraps of fat and grease were put in. everyone was careful not to touch the strong lye, for it would have eaten the skin off one’s fingers. (62) The grease was saved by the housewife from cooking during several months. Then it was put in the large round-bottomed iron kettle with the homemade lye. After boiling the mixture became a mass of jelly-like soap. Then it was allowed to cool, and from it were cut bars of brown soap, which were stored for household use. (63)

Soap Making

Common Fatty Acids To Know

Classification of LipidsG

lyce

rol

FA

FA

FA

Simple and complex lipids

Simple Complex

Classification of Lipids

GlycolipidsGlycerophospholipids

Gly

cero

l

FA

FA

FA

Simple and complex lipids

Simple Complex

Classification of Lipids

GlycolipidsGlycerophospholipids

Gly

cero

l

FA

FA

FA FASphi

ngos

ine

GLUCOSEGALACTOSE

Simple and complex lipids

Simple Complex

Phosphoglycerides Sphingolipids

Classification of Lipids

GlycolipidsGlycerophospholipids

Gly

cero

l

FA

FA

FA FASphi

ngos

ine

GLUCOSEGALACTOSE

Simple and complex lipids

Simple Complex

Phosphoglycerides Sphingolipids

Classification of Lipids

GlycolipidsGlycerophospholipids

Gly

cero

l

FA

FA

FA

Gly

cero

l

FA

FA

PO43- ALCOHOL FASp

hing

osin

e

GLUCOSEGALACTOSE

Simple and complex lipids

Simple Complex

Phosphoglycerides Sphingolipids

Classification of Lipids

GlycolipidsGlycerophospholipids

Gly

cero

l

FA

FA

FA

Gly

cero

l

FA

FA

PO43- ALCOHOL

Sphi

ngos

ine FA

PO43- CHOLINE FASp

hing

osin

e

GLUCOSEGALACTOSE

Sphi

ngos

ine

Simple and complex lipids

Simple Complex

Membranes

• Complex Lipids make up membranes

• Hydrophilic vs. Hydrophobic

Cell Membrane

• Lipid layers line up with alaphatic tails inward• Unsaturation allows for liquid like character of the membrane• Intergral and peripheral proteins are a part of the structure• Cholesteral is also a component of membranes

Transport Through a Membrane

Membranes• Youtube• http://www.youtube.com/watch?

v=GW0lqf4Fqpg• http://www.youtube.com/watch?

v=ULR79TiUj80• http://www.youtube.com/watch?

v=vh5dhjXzbXc• http://www.youtube.com/watch?

v=ooX9hHu5baM

Glycerophospholipids

• Glycerol is the alcohol

• Two acids are Fatty Acids

• Third is esterified to PO43- and choline

• The Fatty Acid on carbon 2 is unsaturated

choline

CH2 CH2OHNH3C

CH3

CH3

+

glycerolH2C

HC

H2C

OH

OH

OH

C (CH2)7 CH

O

HC

H2C

H2C C (CH2)16 CH3O

O

O

O OP

O

O CH2CH2 N CH3

CH3

CH3

CH CH2 CH CH (CH2)4 CH3

-

+

Glycerophospholipids

• Phosphotidylcholines

• Also called “lecithins”

Locate:glycerol portionstearic acidcholinelinoleic acidphosphate

Charged groupsForms lipid bilayer withHydrophobic heads together

Glycerophospholipids• Cephalins

– another type of glycerophospholipids– alcohol is ethanolamine or serine instead of

choline

Glycerophospholipids

• Phosphatidylinositols (PI)

• Alcohol is inositol

• Serve as signaling or

Communication sites

inositol

• Coating of nerve axons (myelin)

• Alcohol portion is sphingosine (not glycerol)– A long chain fatty acid is connected to the NH2

– The End OH group is esterified by phosphorylcholine

Sphingolipids

CH(CH2)12CH3 CH CH CH CH2

OH NH2 OH

sphingosine

Sphingolipids

Can you find the sphingosine????

• Glycolipids contain carbohydrates

• They also use sphingosine

• One type is the cerebrosides– occur in the brain (7% of dry weight!)

– present at nerve synapses

Glycolipids

O

OH

OH

HO

CH2OHO

HNO

OH

a glucocerebroside

Steroids

• A third major class of lipids:

• They are all based on this structure

H3C CH3

CH3

HO

CH3

CH3

cholesterol

Cholesterol– most abundant steroid in the body– cell membrane component– raw material for other

steroids synthesis

• Exists in both free and esterified forms– Esterifies with FA– Gallstones are almost pure cholesterol– Correlation between HI serum levels and atherosclerosis– Necessary for human life– Manufactured in the liver – body keeps a set amount

H3C CH3

CH3

HO

CH3

CH3

cholesterol

Lipoproteins

• Transport cholesterol, and fats

• Types of Lipoproteins– HDL = hi density lipoprotein (the good Kind)

• 33% protein and 30% cholesterol

– LDL = lo density lipoprotein (the not good kind)

• 25% protein and 50 % cholesterol

Steroid HormonesCholesterol is starting material for synthesis

of Progesterone:• Alcohol on C-3 converted

to a ketone• Side chain on D ring modified• Precursor of sex hormones

and adrenocorticoid hormones

C

CH3

O

O

CH3

CH3

progesterone

H3C CH3

CH3

HO

CH3

CH3

cholesterol

Hormones from Progesterone

C

CH2OH

O

O

CH3

HCHO

O

aldosterone

Steroid Hormones

• Aldosterone– Product of the adrenal gland– Mineralocorticoid (regulates ion concentration)– Increased secretion

enhances reabsorption of Na+ and Cl- ions in the kidney tubules

testosteroneO

CH3

CH3OH

Steroid Hormones

• Sex Hormones - Testosterone– Promotes normal growth of male sex organs– Synthesized in testes

from cholesterol– Secretion results in

2nd sex characteristics

Steroid Hormones

• Sex Hormones - Estradiol– Regulates cyclic changes in the uterus– Synthesized from

testosterone– Menstrual Cycle

• increased estradiolat beginning of cycle

• uterus thickens• Luteinizing hormone

triggers ovulationestradiol

HO

CH3OH

YouTube

http://www.youtube.com/watch?v=9oaFmKc3ll0

http://www.youtube.com/watch?v=rBBWMRRWOrM

http://www.youtube.com/watch?v=p_ewmP1L7ro

H3C

HO

CH3

CH3

OH

HOC O

NH

CH2

COO-

glycocholate

Bile Salts

• Bile Salts are oxidation products of Cholesterol – 3 OH’s and an Acid end

• Charged salt is more soluble in solution• Bile salts help disperse dietary lipids in

the small intestine – increase digestion rate• Removes cholesterol

in two ways – they are broken cholesterols and dissolve deposited cholesterol

Prostaglandins

• Fatty acid-like substances

• Produced in prostate– small amounts produced

in all tissue

• Synthesized fromArachidonic Acid

COOH

CH3

Arachidonic Acid

COOH

O

HO OH

CH3

PGE2 (a prostaglandin)

steps

Prostaglandins

• PGE2

– induce labor– therapeutic abortion– lowers bp– used to treat asthma

• PGE2 – causes hypertension

• PGE1

– used as a nasal decongestant

COOH

O

HO OH

CH3

PGE2 (a prostaglandin)

Thromboxanes

O

O

OH

COOH

•Induce Plaelet aggregation

•When a blood vessel is ruptured, platelets congregate and PGH2 causes Them to clot together

Aspirin blocks the effect and acts A blood thinner

PGH2

Prostaglandins / Leukotriene• Leukotrienes

– Occur mainly in leukocytes (white blood cells)

– Long lasting muscle contractions especially in the lungs where they cause Asthma-like attacks

CH3

OH OHOH

COOH

Leukotriene B4