Lipids CH 339 K What are lipids Grab

Lipids CH 339 K

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 H 2 O

Cardiolipin(s) Glycerol Major component of inner mitochondrial membrane (up to 20%) R groups usually c 18: 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 in. Sphingolipid 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 in. Sphingolipid 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 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 H 2 O

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 vd. W contacts (higher Tm) • Unsaturation – Unsaturated FAs fewer vd. W 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