lipids/fatty acids

what are lipids

a broad group of organic compounds that are poorly soluble

what are the components of lipids

a hydrophillic charged head group

a poorly soluble (hydrophobic) tail

can some lipids be amphipathic

yes

what term is used interchangeably with lipids

fats (they are a subgroup of lipids)

what is the function of lipids

its primary function is cell membrane structure but it also plays a role in energy storage

what are some other functions of lipids

insulation (heat)

protection

transportation

signaling molecules (steroids)

hormone synthesis

what do lipid tails have

massive hydrocarbon fatty acid tails that are usually even numbers (4 to 36 carbons long)

can be branched or linear

what is the usual length of hydrocarbon tails on lipids

16-18 carbons long

what are fatty acids

fats and oils that are used as stored forms of energy

what kind of reaction is used with fatty acids

oxidation

is fatty acid oxidation exergonic or endogonic

exergonic (releases energy)

what is the structure of saturated fatty acids

it is linear and contains NO double bonds

it is solid at room temperature

can saturated fatty acids stack on one another

yes

what is an example of a saturated fatty acid

butter

what is the structure of unsaturated fatty acids

it contains one OR more double bonds at the cis (same side) isomer

it is liquid at room temperature

can unsaturated fatty acids stack on one another

not really, the kink in the structure at the double bond makes it more difficult to stack

what is an example of an unsaturated fatty acid

cooking oil

what are trans fatty acids

it is the isomer of unsaturated fatty acid where the double bond is in a trans orientation

it mostly found in processed foods

what is the orientation of trans fatty acids

it contains one or more double bonds in the TRANS (opposite sides) orientation

how are trans fatty acids formed

it is formed from the hydrogenation (addition of H+) of unsaturated fatty acids which linearizes the molecule

what are the similarities of trans fatty acids to saturated and unsaturated fatty acids

it is linear like saturated fatty acids and therefore solid at room temperature (can stack), BUT it still has a double bond like unsaturated fatty acids

what is an example of a trans fatty acid

margarine

how to do lipid nomenclature

describe and write down its systemic name

what does n mean in lipid nomenclature

n = linear molecule

how do you name

what is the carbon skeleton structure

it is a presented ratio where the first number is the number of carbons and the second number is the number of double bonds

Dodecanoic acid has 12 carbons in its chain and it is linear. If this is true what is the carbon skeleton ratio?

12:0

Write the systemic name for 12:0 dodecanoic acid

n-dodecanoic acid

what does delta (Δ) mean in the carbon skeleton

the positions of the double bonds in the hydrocarbon chain

how to do fatty acid nomenclature

bond orientation

bond carbon number

double bonds and orientations

what does no n designation mean

it is a branched hydrocarbon NOT linear

if it is an unsaturated fatty acid what do you need to do

specify the orientation of the double bonds in the SEQUENTIAL order to where they appear in the hydrocarbon chain

cis/trans go first then numbers and name the acid

what do the most commonly occurring fatty acids have for the number of carbons in a linear chain

they have 12 to 24 carbons

where do most double chains often occur

carbon 9, carbon 12, and carbon 15

what usually separates double bonds in fatty acid chains

there is usually methylene (CH2) group separating the double bonds

what is the order of bonds in a fatty acid chain

each double bond is separated by 3 carbons

ie: double single single double

what is the more naturally occurring carbon skeleton chain

18:1 Δ12

how is the fatty acid structure determined

it is determined by the length and degree of unsaturation of the hydrocarbon chain

are hydrocarbons soluble or insoluble in water

hydrocarbons are unpolar and poorly soluble in water

what is more soluble a shorter or longer fatty acid chain

a shorter chain is more soluble

are melting points variable with fatty acid structure

yes

why are melting points variable

the degree of packing can change the melting point bc saturated can pack tightly together minimizing steric hindrance from neighboring atoms while unsaturated fatty acids have too many kinks in its structure to pack properly

what are fatty acids bound to proteins called

lipoproteins

what kinds of interactions do lipoproteins have

noncovalent transient interactions because of the carboxylic acid being negatively charged

the higher the protein to lipid concentration the more the protein is charged

what do most lipoproteins exist as

poorly soluble esters or amides that lack charge and are transported via lipoprotein particles

what are triacylglycerols

the simplest lipids that can be synthesized from fatty acids

three fatty acid chains

what do simple triacylglycerols mean

the fatty acid chains are all identical (usually named after the fatty acid they contain)

how do you name mixed triacylglycerols

name the fatty acids separately and designate a number to each fatty acid chain (the number represents the glycerol carbon the fatty acid is attached to)

are triacylglycerols soluble

no they are poorly soluble

what is the function of triacylglycerols

provide stored energy and insulation

adipocytes

store fatty acids as oil droplets in the cell

white fat cells are used for what

energy storage

brown fat cells (aka baby fat) are used for what

to generate heat

what breaks down triacylglycerols

the enzyme lipase in adipocytes

why are triacylglycerols better than polysaccharides as stored fuels

carbon atoms of fatty acids are more reduced so oxidation of triacylglycerol results in TWICE as much energy

do triacylglycerols or polysaccharides retain water

polysaccharides retain water and triacylglycerols don’t because they are hydrophobic

are triacylglyercols better for aerobic or anaerobic metabolism

they are better for aerobic metabolism (+O-)

vertebrates can store enough fats to sustain energy needs for months

what are phospholipids

lipids that contain a hydrophilic head group and two hydrophobic tails

help with protein activation

what are glycolipids

lipids that contain a carbohydrate group via a glycosidic bond

helps to guide proteins to binding spot strengthening interactions

what are sterols

lipids characterized by a multi ring hydrocarbon structure

lock unsaturated fatty acids into place making the cell membrane more rigid

what are phospholipids

2 fatty acid tails, essential components of neuronal membranes that play a role in maintaining brain structure and function

key component of cell membranes and are amphiphilic/amphipathic

what is the structure of phospholipids

it has a head group w/a contained modified phosphate group (negatively charged)

has a glycerol backbone that has TWO fatty acids connected to it (typically called glycerophospholipids)

what is considered to be the precursor for all glycerophospholipids

phosphatidic acid (highly charged)

most phospholipids are phosphatidic acid w/an additional functional group where the alcohol was

what is the effect of the R group on each phospholipid?

each r group changes the electrostatics of phospholipids which results in unique characteristics/charges