lipids (structure, nomenclature, properties)

lipids are ___ compounds

organic

lipids and water

mostly hydrophobic (nonpolar)

lipids are good for

storage

why are lipids good storage molecules

Stored without a lot of water (not heavy)--> good source of rapid energy when needed by the body

some lipids are _____

amphiphilic

amphiphilic lipids are commonly found in

cell and organelle membranes

define amphiphilic

 both hydrophobic and hydrophilic parts

how does one classify amphiphilic lipids

has not really been determined

lipids are not made up of

monomer units

what are the functions of lipids (7)

• energy storage

• membrane structure

• lubrication and conditioning for body surfaces

• detergents

• signaling molecules

• pigments

• antioxidants

• cofactor for enzymes

lipids ____ compounds

reduced (highly reduced due to high C-H content)

lipids provide ___ kcals/g

9kcals/g

lipid detergent function?

Plays role in digestion of lipids due to emulsification requirements

for signaling, lipids can serve as what

hormones

what are the 2 main categories of hormones they serve as

paracrine and steroid

define paracrine hormones

act locally near cells that secreted them

what does autocrine mean

secreted and utilized within that same cell

steroid hormones act where?

body wide

what vitamins are hormone precursors?

vit A and D

what antioxidants are lipid based? (3)

vit E, beta-carotene, lycopene

how do lipids serve as cofactors for enzymes? (2 examples)

• Vit K: blood clot formation

• Coenzyme Q: electron transport chain

what is the lipid intake in U.S and how does it compare to AMDR?

• intake: 35-40%

• AMDR: 25-35%

based on diet, what is the % intake from different types of lipids?

• 95% TG

• 5% from cholesterol, phospholipids, Fatty acids, and phytosterols

lipids are stored in the body as

fat (adipose)

lipids overall sources in diet?

animal products (majority)

plant sources:

• seeds (sunflower, tree nuts, sesame)

• legumes (peanuts, coconut, soybeans)

• plant tissues (olives, palm)

how are lipids stored in the body

• TAGs in adipose tissue

• skeletal tissue in smaller amounts as smaller droplets

cholesterol and dietary intake**

cholesterol is no longer a component of the dietary guidelines because dietary cholesterol has little impact on disease risk or diseases

raised cholesterol levels are due to the type and amount of saturated fat

FATTY ACIDS

what are FA’s

Made from hydrocarbon chain (hydrophobic) and COOH functional group (hydrophillic)

“-R-COOH”

chemical structure of FA’s

a carboxyl group linked to a hydrocarbon chain

what is a fatty acyl group?

FA in esterified form

what does it mean for an FA to esterified?

when the OH group of the carboxyl end is substituted by another group (aka attached to another molecule)

what is a free fatty acid (FFA)/nonesterified fatty acid (NEFA)?

"free" meaning they are not linked to any other component

maintains the OH group on carboxyl group

what must occur to free fatty acids transported, metabolized, or utilized in aqueous solution

they must be bound to something to have a hydrophilic component

free FA’s are bound to what in the blood

albumin

what enzymes liberate fatty acids from the molecule they are bound to?

lipases

when FFA’s are liberated by lipases, what happens to them

 they must be transported into the cell by a specific protein or transporter

how does one number a fatty acid

start with the carbon on the carboxylic group and work to the other side

how are FA’s classified? (3)

• length

• saturation

• position of = bonds

FA length (# of carbons)

• usually length

• SCFA

• MCFA

• LCFA

• usually length: 2-40C (most 12-24C)

• SCFA: 6 or less

• MCFA: 8-14C

• LCFA: >14

how does chain length affect solubility?

longer chains = less soluble

because longer chain means more hydrophobic area

what does saturated mean

contains the maximum number of atoms bonded to each carbon atom (so no double bonds)

what does unsatured mean?

has at least one double bond

saturation and melting point?

• saturated (no double bonds) has higher melting point than unsaturated (at least one = bond)

• MUFA has higher melting point than PUFA

what is MUFA

FA contains only one double bond

what is PUFA

FA contains more than 1 = bond

Cis and Trans configuration depends on

position of the double bond

what is cis

double bond is on “same side”

aka, the H’s are on same side and causes a kink

what is trans configuration

double bond has hydrogens on opposite sides (creates linear structure)

how does trans configuration impact melting point compared to cis FA

trans FA have higher MP than cis

are able to stack together like saturated FA’s

at room temp, what is the state of saturated and unsaturated FA’s

saturated: solid at room temperature (butter, lard)

unsaturated: liquid at room temperature (olive oil, veg oil)

trans FA’s and health

harmful to us and  no longer generally recognized as safe (GRAS)

promote inflammation, increase risk for diabetes and cardiovascular

trans FA’s and our food supply

no longer allowed due to health effects (were used because very stable)

where are trans fats naturally found?

Ruminants (cows, goats) produce milk --> some of the milk will contain some trans FA in it

Comes from the ruminant (the bacteria used to make the milk in their stomach will produce them). BUT are in really small amounts and do not contribute to CVD or inflammatory risk--> metabolized slightly differently than those found in partly hydrogenated oils

which trans FA is found in milk?

vaccenic acid

humans cannot insert double bond past what C

carbon 9

why cant we insert double bond past carbon 9?

we lack the enzyme delta-9-desaturase

because we cannot make double bonds past C9, which FA’s are essential?

linoleic (18:2n-6) and alpha-linolenic acid (18:3n-3)

FA’s in our diets and most we learn about are in what configuration (cis or trans)?

cis

what is a conjugated double bond

those that occur every 2 Carbons (=-=)

where are conjugated double bonds seen? function?

• in carotenoids (lycopene, b-carotene)

• provide pigment

how do we synthesize long chain FA’s? (basic steps)

desaturation —> elongation —> desaturation (and repeat)

desaturation does what?

adds a double bond (BEFORE C9)

what does elongation do?

adds 2 carbons

alpha linolenic acid leads to the synthesis of what 2 FA’s

eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)

how does ALA become EPA and DHA?

1. ALA (18:3n-3) is desaturated into stearidonic acid (18:4n-3)

2. stearidonic acid (18:4n-3) is elongated into a middle molecule that is 20:4

3. that is then desaturated into EPA (20:5n-3)

4. EPA (20:5n-3) then undergoes one desaturation and one elongation to become DHA (22:6n-3)

what is n-minus nomenclature

ex: 18:3n-3

18 = number of carbons

3 = number of double bonds

n-3 = the first double bond is 18-3 carbons (so at the 15th C)

elongation and desaturation effect on the “n-#”?

does not affect it because we cannot change double bonds past C9

how were the 2 essential FA’s discovered?

1982

• 6 year old female who developed neurological symptoms under PN treatment (an emulsion containing 76% linoleic acid 18:2n-6 and only .66% alpha-linolenic acid 18:2n-3)

• Added alpha-linolenic acid to her emulsion and increased it to 6.9%

• Her serum phospholipids increased drastically and her neurological symptoms were alleviated

• Found out those 2 are essential to receive from diet

what are the saturated FA’s (5)

myristic acid, palmitic acid, stearic acid, arachidic acid, and lignoceric acid

myristic acid (nomenclature)

14:0

palmitic acid (nomenclature)

16:0

stearic acid (nomenclature)

18:0

arachidic acid (nomenclature)

20:0

ligniceric acid (nomenclature)

24:0

what are our unsaturated FA’s (7)

palmitoleic acid, oleic acid, linoleic acid, alpha-linolenic acid, arichidonic acid, eicosapentaenoic acid, docosahexaenoic acid

palmitoleic acid (nomenclature)

16:1n-9

oleic acid (nomenclature)

16:1n-9

linoleic acid (nomenclature)

18:2n-6

sources of linoleic acid

Sources: corn, soybean, safflower, cottonseed, sunflower seed, and peanut oils

linoleic acid is precursor to

arachidonic acid (20:4n-6)

alpha-linolenic acid (nomenclature)

18:3n-3

alpha linolenic sources

soybean and other seed oils

alpha linolenic is precursor for

EPA and DHA

arachidonic acid (nomenclature)

20:4n-6

arachidonic acid sources

small amounts in animal fats

arachidonic acid is made from

desaturation and elongation of linoleic acid (n-6)

eicosapentaenoic acid (nomenclature)

20:5n-3

EPA is found in

marine algae and fish that consume algae

**fatty fish

Docosahexaenoic acid (nomenclature)

22:6n-3

DHA sources

• animal fats as phospholipid component

• marine algae and dish that consume algae (**fatty fish)

• breastmilk and infant formula (needed for formation of NS and memory)

physical properties of FA’s depend of what 3 things

• C-chain length

• degree of unsaturation

• geometry of double bonds

define melting point MP

 the temperature at which the lipid starts to melt

order of melting point for types of FA’s (high to low)

saturated —> MUFA —> PUFA

MP and chain length

MP increases with longer C chain

ex: SFA with 18 C have lower MP than SFA with 24C

fatty acids are how soluble

insoluble (due to hydrophobic chain being > than hydrophilic carboxyl group)

solubility and chain length

solubility decreases as chain length increases

PHOSPHOLIPIDS

What are phospholipids?

Hydrophilic polar head + 2 hydrophobic FA tails

phospholipids will form what in solution

lipid bilayer