Lipids
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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.

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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


(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


Bile Salts

Bile salts are steroid acids


Bile Salts solubilize fats in the digestive tract


  • Derivatives of ArachidonicAcid

  • 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


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