module 8 Flashcards
what are the structural characteristics of lipids?
-are a diverse family of compounds that share the defining feature of insolubility in water
-tend to be a lower molecular weight than other classes of biomolecules
-are distinct from other classes of biomolecules in that they form aggregates rather than polymers
lipids play a number of diverse biological functions including:
-energy storage (fat in animals, oil in plants)
-structural component of membranes
active roles
-signaling (messengers inside cells, between cells, and between tissues)
-enzyme co-factors and vitamins
fatty acids are _____________
hydrocarbon derivatives
what is the general about fatty acids?
-hydrocarbon with carboxylic head
-differ in length and degree of saturation
-usually an even number of C’s (12-24)
what is the general about double bonds within fatty acids?
-saturated (no double bonds)
-unsaturated (1 double bond)
-polyunsaturated (multiple double bonds)
-double bonds usually cis configuration
-double bond usually separated by a methylene group
what is fatty acid nomenclature?
variability points:
-length
-presence or absence of double bonds
-location of double bonds
what are the saturated and unsaturated structures of fatty acids?
hydrocarbon tails of fatty acids associate through hydrophobic and van der Waals interaction
-long chains have a stronger associations than short chains
-saturated chains have stronger associates than unsaturated
what is the association of fatty acids?
-the melting temperature of a fatty acid mixture reflects the length and degree of saturation of the hydrocarbon tails
-double bonds have a greater influence than the length of the tail on fatty acid associations
-longer=higher boiling point
-more double bonds, more likely to stay liquids
how are fats and oils energy storage molecules?
-lipids represent critical energy storage molecules for plants and animals
-lipids occupy most of the intracellular space in adipocytes, the energy storage cells in animal tissue
-the storage of fat under the skin also provides an insulating function for cold weather animals
-fatty acids requires for energy are stored as triacylglycerols
what are triacylglycerols?
fatty acid esters of glycerol
-are the storage lipids in animals and plants
-three fatty acids linked to glycerol through ester linkages
-simply have same three fatty acids at each position, complex have different fatty acids
-the ester linkage removes the polar carboxyl group to make a more hydrophobic molecule
what are different energy storage molecules that serve different biological roles?
-fats represent the key molecules for long term energy storage
-on a gram per gram basis, there is six times as much energy on fats than carbohydrates
what are the characteristics of lipids that make them so effective as long term energy storage molecules?
-low oxidation state
-low hydration state
what is the low oxidation state and low hydration state of fats?
-low oxidation state: less oxygenated fuels burn more efficiently; triacylglycerols have a lower oxygenation state than carbohydrates
-low hydration state: lipids are hydrophobic with limited interaction with water providing a more compact, dehydrated energy storage form
what is saponification (making soap from fat)?
-treatment of fat with a strong base breaks the ester linkages to release dree fatty acids
-the amphipathic properties of free fatty acids make them effective in solubilization of hydrophobic resistance
-fatty acids function as detergents and soaps through formation of micelles that capture hydrophobic molecules
what is Olestra?
-a molecule that looks an taste like fat, but cannot be processed by our digestive system, has potential as a dietary substitute
-consists of eight fatty acids linked to a sugar group
-passes without being absorbed
-offers a low caloric alternative, there are some side effect (leaky butt)
waxes serves as _____________ and ___________
energy reserves and water repellents
what are waxes?
-non-polar esters of long-chain fatty acids and long chain monohydroxylic alcohols
-are very water insoluble and have high melting temps (60-100)
-they are widely distributed in nature as protective waterproof coatings on leaves, fruits, animal skins and feather (ex; cactus, ducks)
what are membrane bilayers?
structural lipids in membranes
-membrane bilayers define cells and regulate the composition of the intracellular environment
-formation of membranes is a spontaneous consequence of the properties of the molecules that compose them
-all mem lipids have polar head and two nonpolar tails
what are the properties of lipids in membranes?
-tend to have similar overall shape and properties : two hydrophobic tails and a hydrophilic head groups
-membrane lipids can be classified based on their backbone (glycerol vs sphingosine) or by their polar head groups (phospho vs glyco)
what are glycerophospholipids?
-most abundant lipids in membranes
-glycerol backbone with a phosphate at the C3 position (glycerol 3-phosphate)
-glycerol-3-phosphate + 2 fatty acids= phosphatidate (or diacylclycerol 3-phosphate)
-the phosphate group is the point of attachment for a variety of polar head groups
what do plant cells often contain? (phosphate availability)
-galactolipids
-sulfolipids
what are sphingolipids?
-derived from sphingosine, a long chain amino alcohol
-structurally, sphingosine is similar to monoacyl glycerol
-single fatty acid linked by amide bond to form ceramide
-structurally, ceramide is similar to diacylglycerol
some common sphingolipids include:
a) sphingomyelins
-phosphocholine
b) cerebrosides
-glycosphingolipid
-single sugar unit
c) gangliosides
-glycosphingolipids
-multiple sugar units
how to glycosphingolipids determine blood type?
-cells are recognized as self vs non-self based on patterns of surface exposed carbohydrates
-transfusion of an incompatible blood type causes severe immunological reaction
-different blood types (A, B, O) reflect different sugar patterns as the head groups of the sphingolipids
what are unique membrane lipids and what are they found in?
-archaebacteria (extremophiles) live under conditions of high temp, pH and ionic strength making it a challenge to maintain membrane integrity
the membrane lipids of extremophiles contain:
-ethers linkages
-branch points withing the hydrocarbon tails
-membrane spanning hydrocarbon tails composed from a single molecules
what are sterols?
-structural membrane lipids
-contain four fused fused steroid nucleus: 3-six carbon rings and 5-carbon D ring
-ring system is rigid and nearly planar
-also serve as precursors for many biologically active products, for ex testosterone
what is cholsterol?
-serves a number of critical biological functions such as mediating membrane fluidity
-also serves as a precursor of steroid hormones and bile salts
what are phosphatidylinositols?
-act as intracellular signal
-phosphatidylinositol 4,5-biphosphate on the inner membrane face
-activations of phospholipase C in response to an extracellular signal triggers the cleavage of head group to produce inositol 1,4,5 triphosphate which increases Ca
-both Ca and diacylglycerol activate specific intracellular pathways and processes
what are the three classes of eicosanoids?
-prostaglandins: constriction of blood vessels
-thromboxanes: involved in blood clot formation
-leukotrienes: smooth-muscle contraction
what is vitamin D?
-regulates Ca uptake and deposition
-can be obtained from the diet or produced endogenously
-endogenous production occurs in a series of reactions, one of which requires UV light
what is vitamin A?
-obtained from liver, egg yolks and milk products
-some animals have sufficient vitamin A in their livers to present a danger to humans if they were to consume them
-exits in 3 forms: alcohol (retinol), aldehyde and retinoic acid
-retinal (aldehyde) is a light-sensitive compound with a role in vision
-Red eye in photos results from retina (and if deficient=night blindness)
what is vitamin E (a-tocopherol)?
-a reducing reagent that scavenges oxygen free radicals
-may prevent damage to fatty acids in membranes
-often used as an additive in cosmetics
-deficiency causes scaly skin, muscular weakness an
d sterility
