Chapter 8 Flashcards
what are lipids
they are a diverse family of compounds that share the defining feature of insolubility in water
how are lipids distinct form other biomolecules
-they tend to be lower in molecular weight then other classes of biomolecules
-they form aggregates rather then polymers
what are some biological roles that lipids play
-energy storage (fat in animals, oils in plants)
-structural component of membranes
-active roles
-signalling (messengers inside cells, between cells adn between tissues
-enzyme cofactors and vitimans
what is the structure of a fatty acid like
-hydrocarbon with carboxylic head
-differ in length and degree of saturation
-usually an even number of C’s (12-24)
how do double bonds within fatty acids effect saturation
-saturated (no double bond)
-unsaturated (1 double bond)
-polyunsaturated (multiple double bonds)
what configuration are double bonds usually in and what group are they usually separated by
-they are usually in the cis configuration
-double bonds are usually separated by methylene group —CH2—
what can points of variability does the nomenclature of fatty acids address
-length
-presents or absence of double bonds
-location of double bonds
how do you use nomenclature to name a fatty acid
(# of carbons:# of double bonds, delta^double bond position)
when naming fatty acids what is delta^n and what is the n
position of double bond inducated by delta^n
where the n is the lowest numbered carbon involved in double bond
when counting the carbons on a fatty acid chain what is carbon 1
the carboxyl group is the carbon 1
how are hydrocarbon tails of fatty acids associated through
hydrophobic and van der waals interactions
what chains have the strongest interactions long chains, short chains, double bond, no double bond
-long chains have stronger associations than short chains
-saturated chains have stronger associates than unsaturated
what does the melting temp of a fatty acid reflect
the length and degree of saturation of the hydrocarbon tails
-the double bond will have agreater influence then the length of the tail on fatty acid association
lipids occupy most of the…
intracellular space in adipocytes
what are adipocytes
the energy storage cells in animal tissues
what does the storage of fat under the skin provide
insulating function for cold weather animals
how are fatty acids used for energy stored as
triacylglycerides
what are triacetalglycerides
the storage of lipids in animals and plants
how are triacetalglycerides constructed
three fatty acids linked to glycerol through ester linkages
what are simple triacetalglycerides made up of and what are complex triacetalglycerides made up of
-simple have the same 3 fatty acids at each position
-complex have different fatty acids
in triacetalglycerides removes what to make a more hydrophobic molecule
ester linkage removes the polar carboxyl group to make a more hydrophobic molecule
what kind of energy storage do fats represent
long term energy storage
how much more energy is there in fats then carbohydrates
on a gram per gram basis about 6x as much energy storage
what are the characteristics of fats that makes it such a good long term energy storage
-low oxidation state
-low hydration state
what is a low oxidation state good for long term energy storage
less oxygenated fuels burn more efficiently; triaceylyglycerols have a lower oxidation state then carbohydrates
why is a low hydration state good for long term energy storage
lipids are hydrophobic with limited interaction with water providing a more compact, dehydrated energy storage form
what is saponification
the treatment of fats with a strong base which breaks the ester linkages to release free fatty acids
the amphipathic properties of free fatty acids make them effective in…
solubilization of hydrophobic substances
how do fatty acids function as detergents and soaps
through the formation of micelles that capture hydrophobic molecules
what is a micelle
an individual wedge shaped (cross section of a head greater than side chain
what is olestra
-it consists of 8 fatty acids linked to a sugar group
-looks and tastes like like fat but passes through the digestive system with out being processed
-offers a low calorie alternative bu there are some side effects
what do waxes serve as
energy reserves and water repellents
how are waxes made up
they are non-polar esters of long-chain fatty acids and long chain monohydroxylic alcohols
what is the solubility and melting temp of waxes
they are very water insoluble and have high melting temps (60-100 C)
where are waxes often seen in nature
as protective waterproof coatings on leaves, fruits, animal skin and fethers
what does the membrane bilayer do
it defines cells and regulates the composition of intercellular environment
what causes the formation of membrane bilayers
it is a spontaneous consequence of the properties of the molecule that compose them
the lipid component of membranes tend to have simular…
over all shapes and properties
how can membrane lipids be classified based off of
there back bone (glycerol vs sphingosine) or by their polar head groups (phospho vs glyco)
what is glycerophospholipids and how are they constructed
-most abundent lipids in membranes
-they have a glycerol backbone with a phosphate at the C3 position (glycerol 3-phosphate)
-the phosphate groups is the point of attachment for a verity of polar head groups
glycerol-3-phosphate + 2 fatty acids =
phosphatidate or diacylglycerol 3-phosphate
what is the most abundant lipid in membranes
glycerophospholipids
what head can glycerophospholipids have and what is the function of them
-there is a variety of different ones they can have
-head groups can carry +, -, or neutral charge
-always polar
-different head groups are likely associated with specilized functions
phosphate is often limiting to plants how do some plants deal with this
-conserve use of phosphate for more critical application (like nucleic acids) some plants use sugar and sulphate polar head groups
-for membrane lipids when it more about the overall p charicteristic they will use the next best thing… sugar or galactolipids
plant cells often contain…
galactolipids and sulfolipids
how are galactolipids constructed
one or two galactose groups linked to C3 diacylglycerol
what are sulfolipids derived from
from sphingosine, a long chain amino alcohol
structrally sphingosine is simular to…
monoacyl glycerol
what is sphingosine constructed of
a single fatty acid linked by amide bond to form ceramide
structurally ceramide is similar to…
diacylglycerol
what are galactolipids, sulpholipids and sphingolipids
they are types of membrane lipid that dont use phosphate
how do cells recognize them self vs not them self
based on patterns of surface exposed carbohydrates
what happens in the case of a incompatible blood type tranfusion
it causes a severe immunological reaction
what doe different blood types reflect
the different sugar patterns as the head groups of the phingolipids
what are archaebacteria (extremophiles)
they live under conditions of high temp, pH and ionic strength making it challenging to maintain membrane integrity
what do membrane lipids of extremophiles often contain
-ester linkages
-branch points
-branch points within the hydrocarbon tails
-membrane spanning hydrocarbon tails composed from a single molecule
what are sterols
they are structural lipids
how are sterols constructed
-sterols contain four fused ring steroid nucleus: 3-six carbon rings and a 5-carbon D ring
-ring system is rigid and nearly planer
what do sterols serve as
precursors for many biologically active products, for example testosterone
what does cholesterol serve as
-its has a number of critical biological functions such as maintaining membrane fluidity
-it also serves and a precursor of steroid hormones and bile salts
how does cholesterol help maintain membrane fluidity
as hydrocarbons are moving around they hit the cholesterol molecule which will dampen out there motion
what are the passive roles of lipids
energy storage and membrane structure
what are the active roles of lipids
-intracellular signalling molecules
-hormones
-enzyme cofactors
-pigments
-vitamins
what do phosphatidylinositols act as
intracellular signalling and contributes to over all architecture in the cell
what side of the cell will phosphatidylinositol 4,5-biphosphate be on
the inside
for phosphatidylinositols what happens when there is a activation of phospholipase C
in responce to an extracellular signal trigger an extra cellular signal triggers the cleavage of head group. and signals to produce inositol 1,4,5 triphosphate witch increases the production of Ca 2+ it binds to ER receptor which activates protein kinase
or
activation of phospholipase C in response to an extra cellular signal triggers the cleavage of head group to produce inositol 1,4,5 triphosphate which increases Ca2+
both Ca2+ and diacylglycerol activate specific intracellular pathways and processes
both Ca2+ and diacylglycerol activate…
specific intracellular pathways and processes
what are eicosanoids
-paracrine hormones (that act on cells near point of production
-derivatives of C20 poly unsaturated fatty acids (arachidonic acid)
-there is three classes of eicosinoids
what are the 3 classifications of eicosnoids and what is there fuctions
-prostaglandins
constriction of blood vessels
-thromboxanes
involved in blood clot formation
-leukotrines
smooth muscle contactions
what are steroid hormones
-hydrophobic oxidized sterol derivatives
-carried through the blood stream by carrier proteins
-they pass through the plasma membrane to bind receptors in the nucleus
-they alter the pattern of gene expression and metabolism
what are the 4 lipid vitamans
A,D,E,K
what do all the lipid vitamans have in common
-they are highly hydrophobic
-they all contain rings and long, aliphatic side chains
why do lipid vitamans have more potential for being dangerous
because they are not water soluble and are stored in fats and are in the body much longer
what does vitamin D do
it regulates Ca2+ uptake and deposition
how can vitamin D be obtained
from the diet or produced endogenously
how is vitamin D produce endogenously
from a series of reactions one of which requires UV light
what are some issues associated with an excess of vitamin D and a deficiency
-insufficient vitamin D is assoceated with skeletal defects (rickets)
-excessive vitamin D can cause calcification of soft tissue
how do we obtain vitamin A
form liver, egg yolks, and milk products
why do some animals have sufficient vitamin A in their livers
to present danger to humans if they were to consume them
what are the 3 forms vitamin A exists in
alcohol (retinol), aldehyde, and retinoid acid
what is retinal (aldehyde)
-it is a light sensitive compound with a role in vision
-“red eye” in photos results form retinal
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 and sterility
what is vitamin K required for
the synthesis of blood coagulation proteins
what is warfarin and what is it used for
-used as rat poison where it causes rodents to suffer uncontrollable bleeding
-vitamin K analogs (such as warfarin) are now given to individuals who suffer excessive blood clotting
like glycerophospholipids a variety of____can be attached to ceramide
polar heads
what are some common sphingolipids
a) sphingomyelins
-phosphocholine
b) cerebrosides
-glycosphingolipids
-single sugar unit
c) gangliosides
-glycosphingolipids
-multiple sugar units
