lipids Flashcards
solubility of lipids
insoluble in water and polar solvents
soluble in non-polar solvents
4 functions of lipids
storage
- stores energy in fats and oils
structural
- protection
- insulation
- membranes
metabolism
industrial uses
structure of fatty acids
hydrophobic hydrocarbon tail - non-polar
hydrophilic carboxyl group head - polar
short chain fatty acids
2-5 carbon atoms
byproduct of fermentation
weak acids
- some polar properties
long chain fatty acids
more than 5 carbons
naturally occurring in even number of carbons
saturated or unsaturated
- very little polar properties
examples of short chain fatty acids (4)
carbon correct trivial
2 - ethanoic acid - acetic acid
3 - propanoic acid - propionic acid
4 - butanoic acid - butyric acid
5 - pentanoic acid - valeric acid
examples of long chain fatty acids (2)
saturated
16 - hexadecanoic acid - palmitic acid - 60.7
18 - octadecanic acid - stearic acid - 69.6
unsaturated
18:1 delta 9 - oleic acid - 16
18:2 delta 9,12 - linoleic acid - -5
18:3 delta 9,12,15 - a-linolenic acid - -11
saturated fatty acids
no c=c double bonds
packed closely and interact
longer chain = more interactions
increase melting point when longer
eg hexdecanoic acid
octadecanic acid
unsaturated fatty acids
1 or more c=c double bond
not straight, bond creates kink
cannot pack closely so fewer interactions
each double bond lowers melting point
cis or trans configurations
trans - hydrogen placed across double bond
cis - hydrogen on same side of double bond (normal)
eg oleic acid
linoleic acid
a-linolenic acid
structure of triacylglycerols
3 fatty acids joined to a glycerol
by an ester bond
neutral molecules
used a energy stores
- seeds of oilseed plants
- adipose tissue of animals
hydrogen of hydroxyl group of glycerol reacts with OH of fatty acid
why do tags make an efficient energy store? (4)
high energy in low weight
- long hydrocarbon chains give high energy
high energy in low volume
- neutral, packed closer than charged molecules, less volume
readily stored and released in hydrolysis and condensation
stores easily distinguish from surrounding material
- non-polar hydrophobic creates lipid droplets
4 reactions of triacyglycerols
hydrolysis
iodination
saponification
hydrogenation
hydrolysis of triacyglycerols
breaking of a covalent bond by the addition of water
essential before energy can be obtained
catalysed by specific lipase enzymes
broken down into glycerol and 3 fatty acid chains
iodination of triacyglycerols
iodine reacts with double bonds in unsaturated chains
interactions breaks double bond and iodine atom bound to each carbon
(hydrogen removed)
saponification of triacyglycerols
formation of soap by heating a triacylglycerol with alkali
fatty acids released
occurs when react with strong bases
releases glycerol molecule
forms salts of fatty acids known as soap
salts of fatty acids produced in saponification
soap formed is amphipathic
allows molecules to form micelles
hydrophobic chains pack together inside
hydrophilic face outwards towards solvent
gives soap its cleaning properties
dirt enclosed within micelle
hydrogenation of triacyglycerols
hydrogen reacts with hydrocarbon chain
double bond broken and hydrogen attaches
removes double bond
increases proportion of saturated fatty acids
increases melting point
use of hydrogenation
transform oil and fats that are liquid at room temperature - hardened
partial hydrogenation used to improve shelf life
cis double bond converted to trans double bond
= trans fatty acids
structure of phosphoacylglycerols
fatty esters of glycerol
with a phosphate and an x group
phosphate replaces fatty acid on carbon 3 of triacyglycerol
linked by phosphodiester bond
what are x groups?
part of a phosphoacyglycerol very polar molecules
often charged
ethanolamine
serine
inositol
choline
what is meant by amphipathic?
a molecule has one polar and one non-polar end
eg phosphoacyglycerols
allows them to arrange in a bilayer
structures formed due to amphipathic nature
monolayer
- at a liquid air interface
- polar heads point down into solvent
- non-polar chains point upwards, away
micelles
- ball with non-polar heads facing inwards
polar heads face out
bilayer
- in an aqueous solution
- polar heads interact and face outwards
- non-poor tails face inwards
what are sterols?
includes cholesterol in animals
stigmasterol in plants
found in membranes
as they are amphipathic
help with keeping structure
increase fluidity
