chapter 15: lipids and fatty acids

lipids consist of

fatty acids or steroid nucleus

lipids solubility

only soluble in organic solvents not in water

lipids important in

cell membrane, fat soluble vitamins, steroid hormones

steroid nucleus fused rings

lipids that are esters that can be hydrolyzed

waxes, fats, oils and phospholipids

• give fatty acids and other molecules

• long chains w/ carboxylic group attached

lipids that can not be hydrolyzed

steroids

• no fatty acids

• four fused carbon rings

fatty acid structures

long unbranched chains w/ carboxylic acid at the end

• 12-18 carbons long

• saturated or unsaturated

fatty acids solubility in water

insoluble due to long carbon chain

saturated fatty acids

single bonds only

lauric acid

found in coconut

myristic acid

nutmeg

palmitic acid

palm

steric acid

animal fat

monounsaturated

only one double bond

palmitoleic acid

butter

oleic acid

olives

polyunsaturated fatty acids

2 or more double bond

linoleic acid

soybean and sunflower

linolenic acid

corn

arachidonic acid

meat, eggs and fish

cis and trans unsaturated fatty acids

• can be drawn as cis and trans isomers

• almost all naturally occurring unsaturated fatty acids have one or more cis double bonds

essential fatty acids

• cannot be synthesized by humans due to amount of polysaturated fatty acids

• linoleic acid (omega 6)

• linolenic acid (omega 3)

• arachidonic acid

deficient in linoleate

mild skin scaling, hair loss and poor wound healing in rats

properties of saturated fatty acids

• fit close together in a regular pattern

• strong dispersion forces between carbon chains

• high melting points and solids at room temp

properties of unsaturated fatty acids

• cis double bond causes a kink = irregular shape

• few interactions between molecules

• low melting point

what is prostaglandins and function

• hormone-like substances produced in cells

• functions: lower or raise blood pressure, stimulate contractions and relax muscle of uterus

prostaglandins also known as

eicosanoids: formed from arachidonic acid

prostaglandins produce

inflammation and pain in a area where tissues are injured

what blocks prostaglandins

NSAIDs

waxes on plants

prevent loss of water and damage from plants

waxes on skin, fur and feathers

provide waterproof coating

waxes structures and parts

esters of saturated fatty acids and long chain alcohols

• 14-30 carbons

have 3 parts

• fatty acid, ester bond, long chain alcohol

beeswax

honeycomb

• used for candles

carnauba wax

Brazilian palm tree

• used for cars

jojoba wax

jojoba bush

• used for soaps, cosmetics

how are fatty acids stored in the body

triacylglycerol

what are triacylglycerols

esters of glycerol and fatty acids

• formed when 3 OH groups of glycerol react with carboxyl group of 3 fatty acids. water is removed

naming triacylglycerols

change glycerol to glyceryl

• name fatty acids as carboxylates (-oate)

major form of energy storage for animals

triacylglycerols

saturated fatty acid melting point

higher than unsaturated

• packed more tightly

melting point of fat and location

• solid at room temp

• comes from animal sources, meat, milk

melting point of oil and location

• liquid at room temp

• comes from plant sources

palm and coconut oil

they consist mostly of saturated acids making them solids at room temperature

vegetable oils have low melting points

high percentage of unsaturated fatty acids than animal fats

hydrogenation reaction

double bonds in unsaturated fatty acids react with H2 to make single bonds

• H2 is bubbled through heated oil in the presence of a catalyst

commercial hydrogenation

• addition of H is stopped before all double bonds are lost

• liquid to a soft semisolid fat

• more saturated = higher melting point

trans fatty acids through hydrogenation

small number of cis double bonds turn into trans double bonds which are more stable

• structure looks like saturated fatty acids

natural trans fatty acids

milk, eggs, beef

trans fatty acids in the body

behave like saturated fatty acids

• raise LDL cholesterol (bad)

• lowers HDL cholesterol (good)

• 2-4% of total calories

t/f: there are more unsaturated fats in vegetable oils

true

t/f: vegetable oils have higher melting points than fats

false

t/f: hydrogenation of oils converts some cis double bonds to trans double bonds

true

t/f: animal fats have more saturated fats

true

hydrolysis meaning

act of separating chemicals when water is added

• OH replaces the OR2 in the ester: leaves you with an acid and a alcohol

triacylglycerols undergoing hydrolysis

splits into glycerol and three fatty acids

• needs a strong acid or enzymes called lipases

types of phospholipids

1. glycerophospholipids

2. sphingomyelin

what is in a glycerophospholipid

glycerol

• 2 fatty acids

• phosphate attached to amino alcohol

glycerophospholipids bonds

• 2 fatty acids that form ester bond with the first and second OH groups of glycerol

• hydroxyl group that forms ester with phosphoric acid which forms another phosphoester bond with an amino alcohol

examples of glycerophospholipids and locations

cephalin: brain and nerve tissues

lecithin: egg yolk, soy and yeast

what is in a sphingomyelin

sphingosine (18 carbon amino alcohol) instead of glycerol

• fatty acid, phosphate and a amino alcohol

sphingomyelin bonds

• amine group of sphingosine forms amide bond to a fatty acid

• OH group forms ester bond with phosphate which bonds another phosphoester bond to choline or ethanolamine

where can sphingomyelin be found

abundant in white matter of myelin sheath

• coating surrounding nerve cells

• increases speed of nerve impulses and insulates and protects nerve cells

steroid nucleus

• 3 cyclohexane rings and 1 cyclopentane ring

• fused

steroid nucleus rings

numbered starting from A

• 2 methyl groups at 18 and 19

cholesterol

abundant steroid in the body

where cholesterol comes from

diet: meats, milk and eggs

synthesized: in the liver

what is cholesterol needed for

cell membrane, brain and nerve tissue, steroid hormones and vitamin D

• clog arteries when in high levels

elevated cholesterol

exceeds 200mg/dL

bile salts found in

synthesized in the liver from cholesterol and stored in gallbladder

• large amounts of cholesterol = gallstones in gallbladder

• help absorb cholesterol

bile salts characteristics

• polar and nonpolar regions - act like soaps to make fat soluble in water

lipoproteins

combined with glycerophospholipids and proteins to form water-soluble complexes

function of lipoproteins

transport nonpolar fats, cholesterol, and triglycerides

• surround nonpolar lipid with polar lipid and protein for transport to cells

• make them soluble in water

examples of lipoproteins

HDL and LDL aka “high/low density”

changing milk to butter process

transforming fat in water emulsion (milk) to a water in fat emulsion (butter)

whole milk

dilute emulsion of fat globules surrounded by lipoproteins membranes that keep fat separate from each other

steroid hormones

chemical messengers: produced from cholesterol that communicate for the body

male sex hormones

testosterone and androsterone

female sex hormones

estrogens and progesterone

adrenal corticosteroids

from adrenal glands

• mineralcorticoids

• glucocorticoids

diffusion

aka passive transport

• high concentration to a low one

facilitated transport

uses proteins channels that increase rate of diffusion

active transport

moves ions against a concentration gradient

• low to high

saponification

reaction of a fat with a strong base in the presence of heat

• forms soaps (salts of fatty acids)

saponification reaction

splits triacylglycerols into glycerol and sodium salts of fatty acids

NaOH with fat

solid soaps

KOH with fat

liquid soaps

cold process to make soap

mix fatty acids and lye (NaOH) together

• high lye: high pH can burn the skin

• not enough lye: greasy soap

• takes 6 weeks

hot process to make soap

no exact measurements

soaps vs detergents

soaps: natural but leave a film and need warm water to work

detergents: manmade and leave no residue and preform well in any temp

surfactants

surface active agents

• reduce surface tension and improve water ability to spread evenly

hard water and soap

forms scum

detergent vs soap structure

detergent: has a ionic group that is manmade

soap: carboxylic acid group