Chapter 10: Lipids

Question 1

what is a fatty acid?

Answer 1

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

Question 2

does a fatty acid tail have an even number of carbons or an odd number?

Answer 2

even

this count includes the carbon in the COO- head

Question 3

which fatty acids have at least one carbon-carbon double bond in the tail: saturated or unsaturated?

Answer 3

unsaturated

Question 4

which carbon-carbon double bonds are more common in fatty acids: cis or trans?

Answer 4

cis

Question 5

how do carbon-carbon double bonds impact the shape of fatty acid tails?

Answer 5

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)

Question 6

barring exceptions and/or metabolic intermediates, what are 3 main properties of fatty acids?

Answer 6

1. even number of carbons
2. cis pi bonds (when applicable)
3. no conjugation/delocalization in polysaturated fatty acids

Question 7

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)?

Answer 7

because conjugation/delocalization would make the double bonds on the fatty acids too stable and thus too difficult to break down/metabolize

Question 8

what is Eicosanoic acid the systematic name for?

Answer 8

Arachidic acid

Question 9

How many carbons does the ‘Eicosa’ prefix in Eicosanoic represent?

Answer 9

20

Question 10

how many carbons are in the saturated fatty acid ‘Lauric acid’?

Answer 10

12

Question 11

how many carbons are in the saturated fatty acid ‘Myristic acid’?

Answer 11

14

Question 12

how many carbons are in the saturated fatty acid ‘Palmitic acid’?

Answer 12

16

Question 13

how many carbons are in the saturated fatty acid ‘Stearic acid’?

Answer 13

18

Question 14

how many carbons are in the saturated fatty ‘Arachidic acid’?

Answer 14

20

Question 15

how many carbons are in the UNsaturated fatty acid ‘Palmitoleic acid’?

Answer 15

16

Question 16

how many carbons are in the UNsaturated fatty acid ‘Oleic acid’?

Answer 16

18

Question 17

how many carbons are in the UNsaturated fatty acid ‘Linoleic acid’?

Answer 17

18

Question 18

which UNsaturated fatty acid behaves more like a saturated fat: cis or trans?

Answer 18

trans

the shape of the kink it causes is more consistent with the extended conformation found in a saturated fat than a cis

Question 19

what are two ways that cis unsaturated fats are different in form and function from saturated fats?

Answer 19

1. the cis kink formed creates a shape inconsistent with the extended conformation shape that saturated fat has
2. the cis kink formed prevents tight packing of the fat

Question 20

where do trans fats come from?

Answer 20

scientists. And bacteria and fungi.

Question 21

why did we invent trans fats come?

Answer 21

to improve shelf life and texture of foods

Question 22

why are trans fats bad for you?

Answer 22

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

Question 23

what are the dominant forces between adjacent fatty acid TAILS that give them order as they transition from liquid to solid at lower temps?

Answer 23

Van der Waal forces
Dispersion forces
Induced dipole forces

Question 24

(other than kinks/tail properties) what 3 factors impact how closely fatty acids pack together?

Answer 24

pH, protonation status, and charge-charge repulsion between the negative head groups

Question 25

why are saturated fats better able to achieve a stable interface/stay stable as solid longer (especially at low temps) than UNsaturated fats?

Answer 25

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

Question 26

pictures of fatty acids usually show the structure in the extended conformation. Is this an accurate representation?

Answer 26

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

Question 27

what is the consequence of a fat being able to achieve a stable interface/stay stable as solid longer ?

Answer 27

higher melting point more heat needed to force the fat from solid phase to liquid phase

Question 28

which fats have higher melting points/need more heat to be forced from solid phase to liquid phase?

Answer 28

saturated fats

Question 29

why can't unsaturated fatty acids achieve a stable interface/stay stable as solid long like how saturated fats can?

Answer 29

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.

Question 30

true or false: more carbons in the fatty acid chain, more q needed to melt

Answer 30

true

Question 31

in addition to limited ability to achieve max surface area for favorable interactions, what other factor impacts the mp point of UNsaturated fats?

Answer 31

the number of carbon-carbon double bond and location of the carbon-carbon double bond

Question 32

True or false: the more saturated a fat is, the more likely it is to be solid at room temp and physiological temp

Answer 32

true

Question 33

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

Answer 33

true

Question 34

in the omega nomenclature convention for fatty acids, where you do start counting from?

Answer 34

the very last carbon in the fatty acid

Question 35

where do the numbers come from in the omega nomenclature convention for fatty acids?

Answer 35

it's the number for the first carbon to have a carbon-carbon double bond you encounter after counting from the terminal (omega) carbon

Question 36

what is so special about omega 3 and omega 6 fatty acids?

Answer 36

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

Question 37

are omega 3 and omega 6 fatty acids polyunsaturated fats?

Answer 37

almost always

Question 38

are omega 3 and omega 6 fatty acids usually cis fats?

Answer 38

yes because of this, they are less likely to clump into plaques, which makes them less precarious than trans fasts

Question 39

all other things (like size) being equal, which kind of fat would allow you to make more ATP: saturated, monosatured, or poly saturated fat?

Answer 39

you get the most ATP by breaking down saturated > monosatured > poly saturated fat the the difference between the 3 is small

Question 40

What is glycerol

Answer 40

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

Question 41

what is the 'acyl' in triacyleglycerol?

Answer 41

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).

Question 42

What 3 functions are fats used for?

Answer 42

energy storage signaling cell membrane structure

Question 43

what is 'lipid' and umbrella term for?

Answer 43

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.

Question 44

Are fats, waxes, oils, and phospholipids types of lipids?

Answer 44

Yes

Question 45

what is an ester

Answer 45

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

Question 46

GENERALLY SPEAKING, what is the difference between 'fat' lipids and 'oil' lipids?

Answer 46

'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