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Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids, oils, triacylglycerols, waxes) Membrane/Structural (Phospholipids, glycolipids, sterols) Signaling, Cofactor, Pigment (phosphatidyinositols, eicosanoids, steroid hormones, vitamins, quinones, dolichols)
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Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

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Page 1: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsLipids are mainly insoluble in water, soluble in organic solventsUses in cell:

Storage (fatty acids, oils, triacylglycerols, waxes)Membrane/Structural (Phospholipids, glycolipids, sterols)Signaling, Cofactor, Pigment (phosphatidyinositols,eicosanoids, steroid hormones, vitamins, quinones, dolichols)

Page 2: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Fatty AcidsHydrocarbon derivatives (highly reduced)Oxidation of fatty acids (CO2 and H2O)is highly exergonicCarboxylic acids with hydrocarbon chains (C4 to C36)Chain can be fully saturated (no double bonds) and unbranchedChain can be unsaturated (double bonds) and branchedNaming #carbons : #double bondsMost common FA have an even number of carbon atomsMost double bonds at C9, C12, C15

Page 3: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Fatty Acids Melting pointsLower for unsat’d because it takes less thermal energy to disorder

unsat’dsat’d

Page 4: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Triacylglycerols (triglycerides, fats)Fatty acid esters of glycerolThree fatty acids each in ester linkage to 1 glycerolInsoluble in water

Page 5: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Triacylglycerols (triglycerides, fats)In vertebrates, adipocytes (fat cells) store lots of triacylglycerols asfat dropletsIn seeds, stored as oils for energyLipases catalyze hydrolysis of triacylglycerols (when need fuel)

How is stored fat better than stored polysaccharides (carbs)?(1) Fatty acids more reduced and oxidation produces 2x energy gramfor gram(2) Fatty acids hydrophobic so no associated water to carry around

Fat stores could meet energy needs for long timeBUT human body can only store less than one day’s energy aspolysaccharide

Page 6: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Triacylglycerols (triglycerides, fats)Some animals use fat stores as insulation (seals, walruses, penguins)Hibernating bears use fat stores as energy and insulation

Sperm whales use fat stores to match buoyancy of their bodies tosurroundings deep under water4 tons oil(triacylglycerols & waxes)Liquid at 37 ˚C, frozen at ~30 ˚C

During deep dives for food oils crystallize and become denserDeep under water, water gets colder and denserBuoyancy of whale changes to match buoyancy of seawater

Page 7: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStorage

Waxes (storage and water repellent)Esters of long-chain (C14 to C36) sat’d and unsat’d fatty acids with long-chain alcohols (C16 to C30)

Plankton - storage of fuelSkin glands - secrete wax to protect hair, skinBirds - secrete wax on feathers to keep them water-repellentPlants - wax to protect against parasites and to prevent evaporation Bees - beehive made of beeswax is water-repellentLanolin - from lamb’s wool used as ointment

Page 8: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

Membrane lipids:Phospholipids - (glycerophospholipids & sphingolipids)hydrophobic region attached to polar group by phosphate

Glycolipids - (sphingolipids & galactolipids)hydrophobic region attached to polar group (sugar)

Sterols - rigid system of four fused hydrocarbon rings

Membrane lipids are amphipathic (amphiphilic) - one end ishydrophobic and the other is hydrophilicDirects packing into micelles, bilayers (membranes), liposomes

Page 9: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

I. Glycerophospholipids (phosphoglycerides)Two fatty acids attached in ester linkage to C1 and C2 of glycerolHighly polar or charged group attached through phosphodiester to C3

Page 10: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

Interesting Phospholipids with ether linkagesFound in animal tissues and some unicellular organisms

Vertebrate heart tissue

LeukocytesStimulates platelet aggregationStimulates serotonin release (vasoconstrictor)Role in inflammation, allergic response

Page 11: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

II. Sphingolipids1 sphingosine, 1 long-chain FA, 1 polar head group

Structural parentof sphingolipids

Phospholipid

Glycolipids

Neu5Ac - N-acetylneuraminic acid (sialic acid) Negative chargeGalNAc - N-acetyl-D-galactosamine

Page 12: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

Sphingomyelin

Plasma membrane of animals

Prominent in myelin (sheath that surroundsand insulates axons of neurons)

Page 13: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

Glyco/SphingolipidsCarbohydrate part of certain sphingolipids define human blood group

Type O (46%) - universal donor, accept blood from OType A (42%) - give blood to A or AB, accept blood from A or OType B (9%) - give blood to B or AB, accept blood from B or OType AB (3%) - give blood to AB , universal acceptor

Page 14: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

Phospholipid and Sphingolipid degradationCells degrade and replace membrane lipids

InfantMental retardation, death

Problems in developmentParalysisBlindnessDeath by 3/4 years old

Page 15: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsStructural in Membranes

III. SterolsPresent in most eukaryotic cell membranes, bacteria cannotsynthesize sterols

Cholesterolamphipathic

Sterols are also precursors toSteroid hormonespotent biological signals that regulate gene expression

Page 16: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

Potent signalers - Hormones

Enzyme cofactors - involved in electron-transfer in chloroplasts andmitochondria

Pigment molecules - conjugated double bonds, absorb visible light,light-capturing in vision and photosynthesisProduce natural coloration of pumpkin, carrots, canary feathers

Page 17: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

PhosphatidyinositolsIntracellular signals

Page 18: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

EicosanoidsParacrine hormones - Carry messages to nearby cellsInvolved in reproduction, inflam, fever, pain, blood clotting, etc.Derived from arachidonic acid, 20:4 (Δ5, 8, 11, 14)Three types: prostaglandins, thromboxanes, leukotrienes

Prostaglandins (PG)First found in prostate gland, stimulatecontraction of smooth muscle of uterusduring labor and menstruation, affect bloodflow, cause fever, inflammation and pain

Thromboxanes (T�BX)Produced in thrombocytes (platelets), act inblood clotting

Leukotrienes (LT)Found in leukocytes, induce contraction ofmuscle lining lung airways, overproduceLTs - asthmatic attacks

Anti-asthmatic (prednisone)

NSAIDS (non-steroidalantiinflammatory drugs) -aspirin, ibuprofen,acetominophen - inhibitsynthesis of PGs and TBXs

Anti-asthmatics - prednisone

Page 19: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

Steroid HormonesOxidized derivatives of sterolAfter synthesis move through blood on protein carriers to targetEnter cell, bind to receptor, trigger effectHormones have high affinity for receptors, so very low concentration needed to produce effect

Page 20: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

Vitamins (Hormone precursors)Needed for health, cannot be synthesized in body, need to get in dietFat-soluble (A, D, E, K)Vitamin DFound in milk, butterVitamin D deficiency - defective bone formation, rickets (need sunlight)Vitamin D3 - formed in skin from 7-dehydrocholesterol & UV lightregulates metabolism of calcium uptake in kidney, intestine, boneVitamin A (retinol)Hormone and visual pigment of vertebrate eyeFound in fish oils, liver, eggs, whole milk, butterβ-carotene (pigment in carrots) can be converted to vitamin ADeficiency - dry skin & eyes, retarded development, night blindness

Retin-ASevere acneWrinkled skin

Helps rod and cone cells in retinarespond to light

Page 21: Lipids - Creightonchemistry.creighton.edu/~jksoukup/lec11STUD2007.pdf · Lipids Lipids are mainly insoluble in water, soluble in organic solvents Uses in cell: Storage (fatty acids,

LipidsSignals, Cofactors, Pigments

Vitamins E and K and Lipid quinones

Vitamin EAssociate with cell membranesDestroy oxygen radicalsFound in eggs, oils, wheat germDeficiency - scaly skin, muscle weakness

Vitamin KUndergoes redox during formation of prothrombinVitamin K deficiency slows blood clottingNewborns given a 1 mg injection of vitamin KK1 found in green plant leaves

Ubiquinoneelectron carriers in the redoxreactions that drive ATPsynthesis in mitochondria andchloroplasts

Warfarin (cumadin)Rat poison - causes internal bleedingAnticoagulant drug to treat those at risk ofblood clotting