1 lipid classification Flashcards
what are the classes of lipids? what are their defining characteristics?
- simple lipids: FAs esterified to an alcohol
- compound lipids: conjugated to a non-lipid moiety
- derived lipids: derived from simple/compound classes
Name examples for each lipid class
- simple lipids: fats, waxes
- compound lipids: phospholipids, glycolipids. lipoproteins
- derived: fatty acids, fatty alcohols, hydrocarbons
name examples for fats and waxes
fats: TGs, edible fats/oils
waxes: fatty alcohol esters, jojoba, cholesterol, vitamin A/retinol, vitamin A ester (wax)
name an example of a phospholipid (hint: eggs)
lecithin
define a fat
- 3 fatty acid (aliphatic) R groups esterified to glycerol.
- aka: triacylglycerol or triglyceride (TG)
- account for >90% of lipids
- oil = lower melting point, liquid at room temp
- fat = higher melting point, solid at room temp
would a pure sample of fat have a wider or narrower range of temperatures over which it melts?
narrower.
pure fats will appear to have an inflection point when graphed
define a wax
- fatty acids esterified to a simple alcohol OTHER than glycerol
- often used as sealing or polishing agents
- found in jojoba as linear monounsaturated FAs esterified to fatty alcohol
- not readily digested; potential fat substitute
- biologically active
define a compound lipid
- simple lipid conjugated to a non-lipid molecule
- includes phospholipids, glycolipids, sphingolipids, and lipoproteins
- can make good emulsifiers (esp phospholipids)
what are the 3 common classes of phospholipid?
- lecithins
- cephalins
- phosphatidyl inositol
define a phospholipid
a TG with one of the FAs replaced with phosphoric acid, which is commonly conjugated to a nitrogenous base
name the classes of phospholipids
- lecithins (phosphatidyl choline): CH2CH2N+(CH3)3
-
what’s a lipid?
substance that is insoluble in water/soluble in non-polar solvents
what class of lipids are fatty acids?
derived lipids
what class of lipids are cholesterols?
simple (wax - FA esterified to a COMPLEX alcohol)
what class of lipid are glycolipids?
compound
what class of lipid are lipoproteins?
compound
what class of lipid are fatty alcohols?
derived
what class of lipid are vitamin A esters/retinol?
simple
what kind of REACTION connects a fatty acid to glycerol?
condensation
what kind of LINKAGE connects a fatty acid to glycerol?
ester linkage
where do you find TGs?
animals: fat cells. Plants: seeds
what differentiates fats from oils?
melting point, which is predominantly determined by their degree of unsaturation
what constitutes a simple acyl glycerol?
if all the FAs are the same length
what constitutes a complex acylglycerol?
if all the FAs are different lengths/saturation
what function do TGs serve?
long-term energy storage/slow delivery, light energy source
what happens to TGs in the intestine?
they get hydrolyzed to free fatty acids by lipases
what happens to TGs if they are hydrolyzed by a strong base?
you get fatty acid salts and glycerol. It’s soap time babeyyy
what’s the difference between acyl-glycerols and waxes?
waxes don’t contain glycerol
Which generally have higher melting points? TGs or waxes?
waxes
what kind of bond links the alcohol with the fatty acid?
ester
what kind of reaction links a fatty acid to an alcohol to make a wax?
condensation
what non-lipid moiety is present on a phospholipid?
phosphoric acid
In phospholipids, what kind of moiety is X?
nitrogenous base
nitrogenous base
phosphatidic acid
respectively, what degree of saturation do the FAs have on the sn1 and sn2 positions of a phospholipid?
saturated, unsaturated
what is phosphatidic acid’s charge at pH 7?
negative
what kind of linkage connects the head group to the glycerol?
phosphodiester linkage
What is X for phosphatidylethanolamine?
O-CH2CH2-NH2
What is X for phosphatidylcholine?
O-CH2CH2-N(CH2)3
what is the net charge of phosphatidylcholine?
0
What is X for phosphatidylserine?
O-CH2-CH(NH2)-COOH
what is X for phosphatidylinositol?
inositol lol. Gotta memorize what that looks like (hexagon with a bunch of OH)
phospholipids comprise of what percentage of the lipids found in food systems?
<5%
Are phospholipids soluble in polar or nonpolar solutions?
both. They’re amphiphilic.
what are lecithins?
emulsifiers; phosphatidylcholines
what are cephalins?
phsophatidylethanolamines
what is X for phosphatidyl glycerol? Where do you find this?
glycerol; green plants esp chloroplasts
what is cardiolipin?
found in beef heart, plant lipid, and bacterial mitochondrial membranes; diphosphatidyl glycerol
what’s plasmalogen?
looks like ethanolamine but with NH3+
what are the components of a sphingolipid?
sphingosine backbone, fatty acid residue, and head group
what degree of saturation is usually present on sphingolipids?
saturated
Specify what X is for each of the following sphingolipids: ceramide, sphingomyelin, glucosylcerebroside, ganglioside
ceramide=H
sphingomyelin=O-CH2CH2-N(CH3)3 aka phosphocholine
glucosylcerebroside=glucose
ganglioside=complex oligosaccharide
where are glyco and sphingolipids found?
membrane in plants and animals
what’s a lipoprotein?
lipid-protein complex
what’s the function of lipoproteins?
circulates in blood to carry lipids for metabolism and storage
expand the abbreviations HDL and LDL
HDL=high density lipoprotein; LDL=low density lipoprotein
HDL vs LDL: which of these is the “good” cholesterol and why?
HDL; carries cholesterol away from vessel walls
what’s the function of LDL?
distributes substances vital to body functions
describe the structure of fatty acid
short of long aliphatic chain with a carboxyl group at the end
what function do short chain FAs serve? (C4, C6, C8)
flavor compounds. Can be good or bad.
what function do long chain FAs serve?
in the presence of mineral salts, tastes soapy
what function do short chain alcohols serve?
flavor compounds
what function do more complex derived FAs serve?
biologically active in the body (ex: cholesterols)
what are terpenes?
derived lipid that makes certain oils fragrant.
which terpenes are most commonly found in essential oils?
mono, sesqui
how many isoprene units are there on monoterpenes? How many carbons?
2; 10
how many isoprene units are there on sesquiterpenes?
3; 15
how much energy is given by 1 g of lipid?
37 kJ or 9 cal
what types of lipids are we most interested in for food systems?
FATS (simple) and PHOSPHOLIPIDS (compound)
what roles does fat play in our diet?
- contributes fat soluble vitamins
- lubricant for food
- satiety/fullness
- heat transfer agent
- shortening in baking
- emulsifiers (mono/diglycerides, phospholipids)
what are emulsifiers? what happens when something’s emulsified?
- substances that stabilizes/reduces interfacial surface tension between hydrophobic/philic components
- increased viscosity, opaqueness; masked fatty sensation
