Chapter 9 - Lipids Flashcards by Kirsten Sawtelle

Hydrolyzable Lipids

Traiglycerols (fats and oils); waxes; glycerophospholipids; sphingolipids (spingophospholipids and sphingoglycolipids)

Assembled from various components - fatty acids combined with other groups: glycerol-based or sphingolipids

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Non-hydrolyzable lipids

Steroids; eicosanoids; fat-soluble vitamins

cannot break down to simpler components

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Palmitic Acid

C16:0

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Stearic Acid

18:0

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Oleic Acid

18:1 (9)

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Linoleic Acid

18:2 (9, 12)

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Alpha linolenic acid

18:3 (9,12,15)

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Essential fatty acids

only obtained via diet (not produced)

Linoleate and linolenic acid

Role: precursors of prostalglandons, eicosanoids, epidermal lipids

membrane lipids

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Tricylglycerols (TAGs)

3 fatty acyl residues esterfied to glycerol

Neutral and extremely nonpolar (great for energy storage!)

Anhydrous and highly reduced (major component of adipose tissue - tight packing)

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Glycerophopholipids

highly amphipathic molecules: 2 fatty acids linked to glycerol-3-phosphate via ester linkages

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Common polar head groups

ethanolamine, choline, serine

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Plasmalogens

glycerol backbone

one ester-linked fatty acid

one vinyl-ether linked fatty acid

concentrated in CNS membranes; muscle, and peripheral nerve tissue

most common head group: choline or ethanolamine

possible function: protecs cell components from oxidative damage (free radicals) via vinyl ether linkage

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Sphingolipids

sphingosine backbone (has amine); abundant in CNS of mammals

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Steroid

Precursor: isoprenoid units and squalene

four fused rings, nearly planar structure, very hydrophobic

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Cholesterol derivatives (features)

Cholesterol esters; bile salts; hormones; certain vitamins (solubility, rigidity, near planar shape)

Shape & functional group arrangement complementary to receptor, aid in digestion of lipids

Nonpolar allows it to get through membrane (some amphipathic)

signaling molecules, non-hydrolyzable, can mix and match rings to get new flavors

ex: stigmasterol (plant sterol); testosterone (steroid hormone); sodium cholate (bile salt); ergosterol (sterol from fungi and yeast)

fat soluble vitames (a, d, e) (a = retinol)

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Cholesterol as related to membrane fluidity

Decreases membrane fluidity because its rigid steroid ring system interferes with the motions of the fatty acid side chains in other membrane liips

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Fluidity of membranes as related to temperature

Fluidity is temp. dependent

At membrane “meltting point” -> transition from ordered crystalline state (gel) to fluid

Solid: Van der waals packing but free rotation; thicker due to stiff, extended tails

To maintain the fluid, dynamic structure: alter fatty acid content of membranes

Basic features and components of other fatty-acid based lipids

e.g. waxes, eicosanoids, and fat-soluble vitamins (some derived from cholesterol)

Waxes: esters of long-chain fatty acids and long-chain monohydroxide alcohols (insoluble in H2O; high mp)

protective waterproof coating on leaves, fruits, skin, etc

Eicosanoids: derived from arachindonic acid; oxygenate variations. Signal molecules: bind to enzymes or proteins for response

Fat-soluble vitamins: A (retinol), E (antioxidant), K (nonpolar lipids)

Functions of Lipids

energy storage, insulation, cushioning

cell compartmentalization

hormones and signaling

Melting Point

Effect of shorter tails and more double bonds

shorter tails - fewer van der waals interactions -> lower melting temp.

more double bonds- more kinking of fatty acid tail ->lower melting temp.

Sphingosine

C18 amino alchol: C1-OH; C2-NH2; C3-OH

Ceramindes

basis of all sphingolipids; fatty acyl group linked to C2 by an amide bond

Sphingomyelins

contains phosphate (only sphingolipid)

phophocholine or ethanolamine at ceramide C1

membrane component (about 10-20% of plasma membrane in lipids)

Cerbrosides and Gangliosides

carboyhydrate instead of phosphate at C1 (no phosphate)

Glycosphingolipids

complex specific tissues and locations in cells no phosphate, only carbohydrate linked to C1-OH

Cerbrosides

monosaccharide at C1 of ceramide (glucose, glactose, etc)

Gangliosides

ceramide with branched oligosaccharide at C1 lots of types found on cell surface about 6% of brain lipids membrane signal and markers problems with degradation responsible for Tay-Sach's and similar diseases

Membrane Rafts

near crystalline regions rich in sphingolipids and cholesterol polar head h-bond cholesterol fills gaps between tails more crytalline entire raft diffuses laterally

Fluid Mosaic Model

olive-oil river, protein-filled treas, sugary skies storm, crazy. Rafts appear and gone. Trees receive quick signals. Ions whiz around and dive in and out of river. Traffic is dizzy. Border is cell membrane. (50% of membrane is proteins)

Protein functions

signaling communication transport metabolic rxns membrane rearranging

Asymmetric distribution of membrane lipids

glycolipids and glycoproteins one extracellular face asymmetry arises from lipid synthesis in the endoplasmic reticulum (plasma membrane in bacteria) by integral membrane proteins mostly on one face.

LIpid composition between leaflets modulated by..

enzyme activity flippases: transport across membrane by facilitated diffusion phospholipid traanslocases: active (atp driven) phospholipid transport across bilayer non-random phospholipid distribution (communicates cell status or type)

Peripheral

soluble, globular proteins associated with membrane; dissociated by high ionic strenth or pH changes

Integral/intrinsic

inserted into or transverse membranes: removed by detergents or chaotropic agents span membrane with an amino acid sequence specific to membrane proteins

Lipid-linked

covalent linkage to lipid group inserted into the membrane.

Alpha helix in membrane as transverse thing

satisfies all polar gorups with h-bonding interacts favorably with nonpolar membrane interior interactions between helices could be polar

Two distinct regions of integral proteins

region emerging from membrane: globular with hydrophobic core. Exterior of cell: modified with glycosylations. Interior of cell: polar with neg. and pos. charged regions inside of membrane -\> hydrophobic surface (few polar groups with associated H2O) ex. Glycophorin

Hydropathy plot

identifies transmembrane helices in proteins

B-Barrel

possible polar interior/hydrophobic exterior 2-22 strands (max. H-bonding - satisfies polar backbone groups) Barrel exterior (band of hydrophobic residues -interior of membrane) hydrophobic band flanked by aromatic aa - interact with polar heads. may be monomers or trimers allow entry of small, polar molecules...can increase specificity by changing the residues.

Linkage of Peripheral protein to membrane surface

Noncovalent - h-bonds and charge-charge interactions Covalent links from amino acids to lipids -\> S, N, or O- linked to amino acids (ex. Cys, Lys, Ser)