2 FAs and TGs Flashcards
what’s the characteristic that most predominantly determines a FAs role?
saturation
What kind of fatty acid is a monounsaturated FA?
omega-9
what are some sources of monounsaturated FAs?
olive oil, avocado, peanuts, almonds
what kind of fatty acids are polyunsaturated FAs?
omega 3 and omega 6
what are some sources of omega 3s?
fish/shellfish (eicosapentaenoic acid and docosahexaenoic acid)
- flax seed/soybean/walnut/rapeseed (alpha-linolenic acid
what is more reactive: a saturated or unsaturated FA?
unsaturated (double bond is a better source of electrons)
do FAs mostly have an even or odd number of carbons?
even
what odd number FAs are present in milk?
pentadecanoic and heptadecanoic (15 and 17)
what # carbon range is miscible with water?
C4-C8
what are the most common unsaturated FAs?
oleic, linoleic, linolenic
in the FA naming system, what do the ##s mean in ##:## (####)
No. carbons:degree of unsaturation (where the db is)
How would you name an 18-carbon FA with a cis double bond on the 9 position and a trans double bond on the 12 position? What’s its shorthand?
octadeca-cis-9-trans-12-dienoic acid; 18:2(9c,12t)
what conformation, cis or trans, are FAs most often found in nature?
cis
why do the presence of double bonds decrease a FA’s melting point?
creates kink in chain leads to a more unstably packed lattice
what is the name of the process that converts cis forms of FAs to trans?
hydrogenation
what happens as a result of hydrogenation?
oils become plastic; metabolized similarly to saturated FAs
when the double bond in oleic acid is converted to trans, what’s the name of this new FA?
elaidic
which is more commonly found in nature? Conjugated or unconjugated bonds? Why?
unconjugated. Conjugated are more likely to undergo autooxidation
what is reversion?
associated with soybean/fish oils. It’s when there’s an appearance of objectionable flavor from less oxidation than what’s normally required. Results from a mixed bonding system which leads to an active methylene group.
what is the crystal lattice stabilized by?
hydrophobic interaction along acyl residues
a fatty acid’s ability to ____________ determines its melting point
pack
when is the only situation in which a cis double bond will increase the melting point?
when it’s on the terminus of a carbon chain
what assumption does the omega naming system make?
all double bonds are cis; double bonds are unconjugated
consider C10:2 ω3. How many carbons? How many double bonds? Where are the double bonds?
10, 2, starting from the CH3 end, on positions 3 and 6.
how many conjugated bonds does natural linoleic acid have? Where are they?
2 on the 6 and 9 positions from the ω end
how many conjugated bonds does arachidonic acid have? Where are they?
4 on the 6, 9, 12, and 15 positions from the ω end
ω3 FAs are what type of FA?
linolenic
ω6 FAs are what type of FA?
linoleic
ω9 FAs are what type of FA?
oleic
give an example of a FA that belongs to the ω9 group
Erucic acid (mustard)
give an example of a FA that belongs to the ω6 group
arachidonic acid (meat, liver, lard, lipids of chicken and eggs)
give an example of a FA that belongs to the ω3 group
C20-22 FAs (fish lipids)
which ω types are considered essential fatty acids?
ω3 (linolenic) and ω6 (linoleic)
what’s so fancy about CONJUGATED linoLEIC acids (CLAs)?
they are attributed to having anti-carcinogenic effects
what’s the most common CLA?
cis-9-trans-11-octadecanoic acid (rumenic acid)
what are the names of the 2 PUFAs with trans double bonds that you have to know?
Elaidic, linoelaidic.
where are the trans bonds located in elaidic and linoelaidic acids?
tr9, tr9 and tr12
what isn’t commonly found in natural FAs?
branched hydrocarbons, hydroxy acids, cyclic FAs, and acetylenic FAs
give an example of a FA with branched hydrocarbons
malvalic acid. Also found in microorganisms
give an example of a FA containing a OH group on its chain
ricinoleic acid
what makes hydroxy acid FAs potentially useful?
their very reactive OH side chain
what are acetylenic FAs used for?
antifungals
name some examples of simple TGs
tristearin, triolene
name some examples of mixed glycerides
stearodilinolein, dipalmitolinolenin, palmitostearolinolein
what are the 4 steps to analyzing the composition of TGs?
1) extract fats
2) saponify using NaOH
3) methylate the FAs with methanol –> fatty acid methyl esters (FAMEs) which are volatile then proceed to use GC
4) identify/quantify against known FAME standards
what are common plant sources of fats?
seeds and fruits. Particularly soybean, rapeseed (canola), peanut, olive, coconut, palm, biproducts of corn and cottonseed. Nonedible: castor oil and linseed (flax) oil
what’s the edible version of linseed oil called?
linola
what are the non-edible oils often used for
what are the non-edible oils often used for
what are some common animal sources for fat?
by-products of meat production from cattle, hogs and sheep; milk of ruminants; fish (esp sardines, herring, menhaden)
what are the distinguishing features of the milkfat group?
- comes from milk of ruminants (cow, goat, sheep, yak, water buffalo)
- high levels of LONG chain SATURATED fatty acids.
- substantial amount of short chain fatty acids (C12 and C4) responsible for potentially desirable rancid flavors
- most unsaturated bits are in TRANS form due to bio-hydrogenation
• High to low: oleic, palmitic, stearic, butyric & other short chains
what are the distinguishing features of the lauric acid group?
- “tropical oils”
- high content of lauric acid (40-50%)
- mostly saturated
- oils at room temp due to high portion of C12
- resistant to oxidative rancidity due to low degree of unsaturation (aka mostly saturated) so long shelf life
- can be fractionally crystalized
what are the distinguishing features of the oleic/linoleic acid group?
- predominantly composed of 18:1 and 18:2
- sat fats make up <20%
- not much 18:3 therefore little reversion –> more shelf stable
- can be partially hydrogenated to become more plastic
what are the distinguishing features of the linolenic acid group?
predominantly composed of 18:3, usually in conjunction with oleic and linoleic groups; “drying oils” – they have the ability to polymerize into a hard film (like paint) when applied in a thin layer; ex) soybean, castor, linseed, hempseed, perilla oil
• Soybean was originally a drying oil but then got developed into an edible one
• Can undergo REVERSION – rapid transition of bland, tasteless oil shortly after processing
what are some distinguishing features of the animal fat depot group?
lard from pigs/tallow from sheep & cows; higher melting points due to fatty acid distribution; 50-60% oleic and linoleic acid; as a higher ratio of desaturated (gs2u) and trisaturated (gs3) glycerides than oleic/linoleic group30-40% palmitic and stearic acid.
what are distinguishing features of the marine oil group?
low sat fat, high long chain FAs; can be very unsaturated; very susceptible to autoxidation
what are distinguishing features of the erucic acid group?
rapeseed/mustard oil; high 22:1 content; rapeseed has 40-50% erucic acid; can be converted to canola
as chain length increases, melting point __________
increases
as chain length increases, volatility __________
decreases
as chain length increases, water solubility __________
decreases
as degree of unsaturation increases, melting point __________
decreases
