Lipid Nomenclaure Flashcards
what are the 5 functions of lipids?
- components of cell membranes
- concentrated energy stores
- vitamins
- hormones
- intracellular messengers
- lipids are energy source when glucose stores aren’t available
- vitamin D is a lipid derived from cholesterol
- steroid hormones are lipids derived from cholesterol
- can act as inflammatory response: many anti-inflammatory drugs target lipid metabolism
what are the chemical properties of lipids? hydrophobic or philic?
generally non-polar and aren’t miscible with water and have low solubility in water
the exception is amphipathic lipids which are polar (ex. phospholipids in cell membranes)
what’s the structure of amphipathic lipids?
- glycerol backbone
- polar group: phosphate attached to alcohol
- two fatty acid chains
what shape does a group of triglycerides take?
fat reserves in the form of neutral triglycerides can form as droplets in the adipose cells
these hydrophobic droplets are ideal for energy storage and are used in times of metabolic demand when glucose and glycogen stores are depleted
triglycerides have 3 FA chains
what are liposomes?
when a phospholipid bilayer forms a circle
useful for extended release drug delivery because you can put polar drugs in the middle and non polar stuff in the bilayer and then the liposome merges with the cell membrane of a cell and releases the drugs
what shape do amphipathic lipids with single hydrocarbon FA chains prefer?
micelles
what are the common characteristics of fatty acid structure?
- carboxyl group at one end (COO-)
- methyl group at the other end (CH3)
- hydrocarbon chain in the middle that can be saturated or not (n=0-24)
CH3(CH2)nCOO-
when does the carboxyl group of a FA ionize?
pH=7 (pK = 5)
COO- at physiological pH
what are the two ways to name FA?
- systemic names
2. common names (on food labels)
what are systematic names of FA?
based on the number of carbons in the chain length
use Greek prefixes
ex. n-dodecAnoate = 12 carbons
ex. n-tetradecAnoate = 14 carbons
ex. n-hexadecAnoate = 16 carbons
ex. n-octadecAnoate = 18 carbons
the capitalized A in -anoate indicates a saturated FA without double bonds
what nomenclature indicates a saturated FA?
the a in -anoate
ex. dodecanoate
what’s the common name for n-octadecanoate?
stearate
what’s the common name for n-tetradecanoate?
myristate
what’s the common name for n-hexadecanoate?
palmitate
what are unsaturated FA? what are they called?
unsatured FA has at least 1 double bond in the hydrocarbon chain so the chain is no longer saturated with hydrogen bonds
unsaturated FA are called mono (1 double bond) or poly (2-6 double bonds) unsaturated fats
what is the nomenclature for unsaturated FA?
-enoate
a prefix before the -enoate indicates the number of double bonds (di, tri, etc.)
ex. hexadecenoate = 16 carbon with 1 double bond
ex. hexadecadienoate = 16 carbon with 2 double bonds
what is C1 in a FA?
carboxyl carbon (COO-) is C1
what are C2 and C3 in FA?
the carbon next to C1 moving towards the methyl CH3 carbon is C2 = alpha carbon
C3 is the next carbon over and is called the beta carbon
what is the methyl carbon in FA called?
omega carbon
for FA that have an omega in the name, the carbon counting starts from the methyl (omega) carbon instead of the carboxyl carbon
how do you express the positions of double bonds?
OLD WAY:
Δx where x indicates the first carbon of the double bond counting from C1 (carboxyl end
ωx where x indicates the first carbon of the double bond counting from the omega end
CURRENT WAY:
A:B(x,y,z) where A is the chain length, B is the number of double bonds and x,y,z is the positions of double bonds from carboxyl end
A:B(ω,w,z,y) where ω,w,z,y is the positions of double bonds from methyl end
what are the various nomenclatures for octadecadienoate? (aka linoleate)
cis-Δ9,12-octadecadienoate
cis-ω6,9-octadecadienoate
18: 2(9,12)
18: 2(ω6,9)
which FA are common in the diet and in FA metabolism in mammals?
myristate 14:0
palmitate 16:0
pamitoleate 16:1(9) or ω7
stearate 18:0
oleate 18:1(9) or (ω9)
linoleate 18:2(9,12) or (ω6,9)
linolenate 18:3(9,12,15) or (ω3,6,9)
arachidonate 20:4(5,8,11,14) or (ω6,9,12,15)
do saturated or unsaturated FA have higher melting temperatures?
saturated FA have higher Tm because they pack better than FA with double bonds that cause kinks in the packing
which numbers of FA are solid at room temperature and body temperature?
FA with 14-18 carbons are solid at room temperature and body temperature
once you add double bonds the melting points decrease a ton!
food manufacturers have trouble making fats like margarine or butter spreads from polyunsaturated FAs such that they saty as solids at room temperature
what is partial hydrogenation?
saturating double bonds in unsaturated FA
that makes them more solid but changes these fats into very unhealthy food ingredients
what’s the usual conformation of double bonds in unsaturated FA? what does this cause? how can you switch between the cis and trans forms?
cis
cis conformation causes hydrocarbon chains to become kinked and shortened so they behave in a more fluid manner = lower melting points
trans conformations have a much higher melting point and their properties are more like saturated FA
the change from cis to trans can happen during hydrogenation
what is hydrogenation?
heat + catalyst + unsaturated FA can cause changes in the nature of the double bond and reconfigure it to a trans bond increasing the Tm and conferring properties of a saturated FA
what’s the problem with trans FA?
they negatively affect serum lipid levels, FA metabolism and endothelial function
trans FA increase mortality, coronary heart disease mortality and cardiovascular disease incidence
which FA are actually though to be cardioprotective?
omega-3 FAs
EPA and DHA are two FA in omega-3 fish oil supplements that are very long chain FA with lots of double bonds and they’re not harmful with respect to heart disease! people actually think they help
- decrease blood triglycerides
- decrease platelet adhesion = less strokes
- increase nitric oxide = blood vessel dilation
- decrease ischemic myocardial damage/inflammation
- decrease restenosis after angioplasty (high doses)
