Chapter 10: Lipids Flashcards
what is a fatty acid?
a type of lipid composed of a polar carboxylic acid head (deprotanated at physiological pH) and a long, very hydrophobic hydrocarbon tail
chain/tail which may be straight or branched, saturated or unsaturated
does a fatty acid tail have an even number of carbons or an odd number?
even
this count includes the carbon in the COO- head
which fatty acids have at least one carbon-carbon double bond in the tail: saturated or unsaturated?
unsaturated
which carbon-carbon double bonds are more common in fatty acids: cis or trans?
cis
how do carbon-carbon double bonds impact the shape of fatty acid tails?
it kinks them (because pi bonds aren’t able to engage in constant free motion/freely rotate and thus impart a rigidity in the regions of the tail where they are located)
barring exceptions and/or metabolic intermediates, what are 3 main properties of fatty acids?
- even number of carbons
- cis pi bonds (when applicable)
- no conjugation/delocalization in polysaturated fatty acids
why do we care that double bonds in polyunsaturated fats are always separated by at least one tetrahedral carbon and are never close enough together to be conjugated/delocalized (according to Dr. Shimko)?
because conjugation/delocalization would make the double bonds on the fatty acids too stable and thus too difficult to break down/metabolize
what is Eicosanoic acid the systematic name for?
Arachidic acid
How many carbons does the ‘Eicosa’ prefix in Eicosanoic represent?
20
how many carbons are in the saturated fatty acid ‘Lauric acid’?
12
how many carbons are in the saturated fatty acid ‘Myristic acid’?
14
how many carbons are in the saturated fatty acid ‘Palmitic acid’?
16
how many carbons are in the saturated fatty acid ‘Stearic acid’?
18
how many carbons are in the saturated fatty ‘Arachidic acid’?
20
how many carbons are in the UNsaturated fatty acid ‘Palmitoleic acid’?
16
how many carbons are in the UNsaturated fatty acid ‘Oleic acid’?
18
how many carbons are in the UNsaturated fatty acid ‘Linoleic acid’?
18
which UNsaturated fatty acid behaves more like a saturated fat: cis or trans?
trans
the shape of the kink it causes is more consistent with the extended conformation found in a saturated fat than a cis
what are two ways that cis unsaturated fats are different in form and function from saturated fats?
- the cis kink formed creates a shape inconsistent with the extended conformation shape that saturated fat has
- the cis kink formed prevents tight packing of the fat
where do trans fats come from?
scientists. And bacteria and fungi.
why did we invent trans fats come?
to improve shelf life and texture of foods
why are trans fats bad for you?
body cannot break them down because that rigid, trans carbon-carbon double bond they have helps them pack tightly together into ‘plaques’ in places like arteries
what are the dominant forces between adjacent fatty acid TAILS that give them order as they transition from liquid to solid at lower temps?
Van der Waal forces
Dispersion forces
Induced dipole forces
(other than kinks/tail properties) what 3 factors impact how closely fatty acids pack together?
pH, protonation status, and charge-charge repulsion between the negative head groups
why are saturated fats better able to achieve a stable interface/stay stable as solid longer (especially at low temps) than UNsaturated fats?
saturated fats’ extended conformation maximizes the tails’ non-polar surface area, thereby excluding water/generating a fully enveloped binding area and maximizing the number of favorable intermolecular interactions that can be made between adjacent tails (via Van der Waal forces, Dispersion forces, and Induced dipole forces)
This is especially true when lower temperatures reduce the tails’ “flipping and flopping” and causes them the settle into their extended conformation
pictures of fatty acids usually show the structure in the extended conformation. Is this an accurate representation?
No. The single bonds are all in constant motion/free to rotate freely so in real life, the structure’s shape is generally more like a squiggly spaghetti… EXCEPT at temperatures low enough to slow the structure’s movement such that it holds still in its extended conformation shape
what is the consequence of a fat being able to achieve a stable interface/stay stable as solid longer ?
higher melting point
more heat needed to force the fat from solid phase to liquid phase
which fats have higher melting points/need more heat to be forced from solid phase to liquid phase?
saturated fats
why can’t unsaturated fatty acids achieve a stable interface/stay stable as solid long like how saturated fats can?
the kinks from the carbon-carbon double bonds reduce the fat’s ability to adopt extended conformation, which reduces non-polar surface area on the tails, which reduces opportunities for the favorable interactions needed to create the stable interfaces between tails needed to maintain an ordered/solid state
this is especially true when you have saturated fats and UNsaturated fats mixed together.
true or false: more carbons in the fatty acid chain, more q needed to melt
true
in addition to limited ability to achieve max surface area for favorable interactions, what other factor impacts the mp point of UNsaturated fats?
the number of carbon-carbon double bond
and
location of the carbon-carbon double bond
True or false: the more saturated a fat is, the more likely it is to be solid at room temp and physiological temp
true
True or false: the more UNsaturated and polyunsaturated fat is, the more likely it is to be liquid/oil at room temp and physiological temp
true
in the omega nomenclature convention for fatty acids, where you do start counting from?
the very last carbon in the fatty acid
where do the numbers come from in the omega nomenclature convention for fatty acids?
it’s the number for the first carbon to have a carbon-carbon double bond you encounter after counting from the terminal (omega) carbon
what is so special about omega 3 and omega 6 fatty acids?
omega 3s are needed to make the fatty acid ‘Arachidonic acid’
omega 6s are some of the regulators in the production of the fatty acid ‘Arachidonic acid’
we need Arachidonic acid for giving flexibility to cell membranes
are omega 3 and omega 6 fatty acids polyunsaturated fats?
almost always
are omega 3 and omega 6 fatty acids usually cis fats?
yes
because of this, they are less likely to clump into plaques, which makes them less precarious than trans fasts
all other things (like size) being equal, which kind of fat would allow you to make more ATP: saturated, monosatured, or poly saturated fat?
you get the most ATP by breaking down saturated > monosatured > poly saturated fat
the the difference between the 3 is small
What is glycerol
Glycerol is a naturally occurring 3-carbon alcohol in the human body. It is the structural backbone of triacylglycerol molecules, and can also be converted to a glycolytic substrate for subsequent metabolism
what is the ‘acyl’ in triacyleglycerol?
An acyl group is a functional group with formula RCO- where R is bound to the carbon atom with a single bond.
Acyl groups are formed when one or more hydroxyl groups are removed from an oxyacid (acid with form X-OH).
What 3 functions are fats used for?
energy storage
signaling
cell membrane structure
what is ‘lipid’ and umbrella term for?
lipid is an umbrella term for a large and diverse group of naturally occurring organic compounds that are related by their solubility in nonpolar organic solvents and general insolubility in water.
Are fats, waxes, oils, and phospholipids types of lipids?
Yes
what is an ester
Esters are a functional group commonly encountered in organic chemistry. They are characterized by a carbon bound to three other atoms: a single bond to a carbon, a double bond to an oxygen, and a single bond to an oxygen
GENERALLY SPEAKING, what is the difference between ‘fat’ lipids and ‘oil’ lipids?
‘fat’ lipids are generally saturated, solid at room temp, and have high melting point (hot like the frying pan)
‘oil’ lipids are generally UNsaturated, liquid at room temp, and have low melting point
