Lipids
CH339K
What are lipids?
• Grab bag of molecular types
• Common link is their hydrophobicity
– Fats
– Glycerophospholipids
– Sphingolipids
– Waxes
– Eicosanods
– Steroids
– And other stuff
F
A
T
T
Y
A
C
I
D
S
You can’t make fatty acids where the double bond is 6
carbons or closer to the end of the molecule
In living systems, the double bonds of unsaturated
fatty acids are usually cis-.
Melting Temps of Fatty Acids
Saturated
Formula
CH3(CH2)10CO2H
CH3(CH2)12CO2H
CH3(CH2)14CO2H
CH3(CH2)16CO2H
CH3(CH2)18CO2H
Common Name
lauric acid
myristic acid
palmitic acid
stearic acid
arachidic acid
Unsaturated
Melting Point
Formula
45 ºC
CH3(CH2)5CH=CH(CH2)7CO2H
55 ºC
CH3(CH2)7CH=CH(CH2)7CO2H
63 ºC
CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO2H
69 ºC
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7CO2H
76 ºC
CH3(CH2)4(CH=CHCH2)4(CH2)2CO2H
Common Name
palmitoleic acid
oleic acid
linoleic acid
linolenic acid
arachidonic acid
Melting Point
0 ºC
13 ºC
-5 ºC
-11 ºC
-49 ºC
(Glycerol tripalmitate)
Grandma’s Lye Soap (Saponification)
Fatty Acid Salts are Amphipathic
Waxes
Very often – fatty acid + long-chain alcohol.
Plant leaf cuticle
Insect
epicuticle
Beeswax components
Spermaceti
•Largely cetyl palmitate
•Large whale may have 3 tons
•May function as lens in
echolocation
•May function as shock absorber
in combat
•Sank the whale ship Essex in
1820
What happens if I substitute something else for a
fatty acid in a fat?
Like a Phosphate?
This also is Amphipathic
Phospholipids in H2O
Cardiolipin(s)
Glycerol
Major component of inner mitochondrial membrane (up
to 20%)
R groups usually c18:2
Major component in heart muscle membranes
Causes platelet aggregation and vasodilation (inflammatory mediator).
Important to the process of hemostasis.
Important in implantation.
Concentration of 10-12 M causes life threatening inflammation of the airways
(asthma-like symptoms).
Toxins such as fragments of destroyed bacteria induce synthesis of PAF
causes drop in blood pressure
reduced volume of blood pumped by the heart
shock and possible death.
Glycolipids
Archaea have weird membrane lipids
Archaean membrane lipids
Polymers of
isoprene
Sulfolobus solfataricus
Sphingolipids
Sphingosine by itself
Defective ganglioside digestive enzymes cause disease
Tay-Sachs – a Defect inSphingolipid Metabolism
As a child with Tay-Sachs grows older, he or she may become blind,
mentally retarded, paralyzed, and unresponsive to the environment. The
child also may have seizures, difficulty swallowing, and difficulty breathing.
Children with Tay-Sachs disease rarely live beyond 4 or 5 years of age.
Tay-Sachs – a Defect inSphingolipid Metabolism
Mutation in lysosomal enzyme Hexosaminidase A
Cholesterol
Steroid
Hormones
Steroid
Testosterone
Estradiol
Cortisol
Aldosterone
Prednisolone
Prednisone
Function
Boys
Girls
Turns on gluconeogenesis
Inhibits immune response
Turns on Metabolism
Increases sodium retention
Increases potassium
secretion
Increased blood pressure
Inflammatory and
autoimmune diseases
Immunosuppressant
Source
Testis (ovary)
Ovary (testis)
Adrenal Cortex
Adrenal Cortex
Drug
Drug
Bile Salts
Bile salts are
steroid acids
Bile Salts solubilize fats in the digestive tract
Derivatives of Arachidonic Acid
• Leukotrienes – conjugated double bonds
•vasoconstrictors
• Thromboxanes – 6-membered ring
•Clot formation
• Prostaglandins – 5-membered ring
•Many functions
•Inflammatory response
•Vasodilators
•Pyogenic
Prostacyclin
Eicosanoid functions
• Prostaglandins have 5- or 6-membered ring
– Short-range hormones mediating (among other
things) pain and inflammation, uterine contraction
• Prostacyclins have a double ring structure
– Inhibit clotting, vasodilators
• Thromboxanes are made in platelets, contain
oxygen in the ring
– Vasoconstrictors, hypertensives, aggregate platelets
• Leukotrienes have 3 conjugated double bonds
– Asthmatic, allergic, and inflammatory responses
NSAIDs like aspirin, ibuprofen, and naproxen
inhibit eicosanoid formation
Phospholipids in H2O
Lipid Bilayer
Cell Membrane
Integral and Peripheral Proteins
Membrane Functions
Membrane Composition
Membrane Composition
Erythrocyte Membrane – differences between inner and outer layers
2-Dimensional Fluids
Membranes exist in 2 states
Phase transition
Factors Impacting Tm
• Chain length
– Longer chains  more vdW contacts (higher Tm)
• Unsaturation
– Unsaturated FAs  fewer vdW contacts (lower Tm)
• Size / Charge of head groups
– Big head groups  steric interference lower Tm)
– Charged head groups  electrostatic repulsion lower
Tm)
• Cholesterol
– Interferes with packing at low temps
– Stiffens membrane at high temps
– Broadens melting curve
Some organisms change their membrane
composition seasonally in order to maintain
constant fluidity
Egregia menziesii
Winter Spring Summer
Fall
SFA
29.6
35.6
34.1
31.4
MUFA
13.3
17.8
16.7
16.3
PUFA
57.1
46.9
49.3
52.3