2005-2006

Lipids

5. lipids:1. have little or no affinity for water2. contain C, H, O sometimes P 3. H:O never 2:14. types – fats, oils, phospholipids, steroids,

and waxes

neutral lipids (a.k.a. triglycerides, fats, or oils) =

3 fatty acids + 1 glycerol molecule

2005-2006

LIPIDS Lipids are composed of C, H, O (same elements

as carbs but very diff structure/proportions & therefore very different biological properties)long hydrocarbon chain

Diverse groupfatsphospholipidssteroids

Do not form polymersbig molecules made of

subunit smaller moleculesnot a continuing chain

FATS Structure: what makes them

hydrophobic?: carboxyl groupglycerol (3C alcohol) + fatty acid

dehydration synthesis

fatty acid = long HC “tail” with COOH group at “head”

FAT Triacylglycerol (big fat molecule!!)

3 fatty acids linked to glycerol ester linkage = between OH & COOH

DEHYDRATION SYNTHESIS (PULLING THE WATER OUT TO FREE UP THE BOND)

FATS (Q: WHAT HAPPENS WHEN YOU ADD OIL TO WATER?)

Long HC chainpolar or non-polar?hydrophilic or hydrophobic?

Function:energy storage

very rich 2x carbohydrates

cushion organs insulates body

think whale blubber!

“Let’s go to the video tape!”(play movie here)

SATURATED FATS AND UNSATURATED FATSSaturated no double bonds found

between carbon atoms on the fatty acid chains

solid at room temperature at room temp., the

molecules are packed closely together

high melting point i.e. butter

Unsaturated one or more double bonds

present between carbon atoms on the fatty acid chains

liquid at room temperature at room temp., the

molecules cannot pack together closely enough to solidify because of the kinks caused by the double bonds

low melting point i.e. olive oil

SATURATED OR UNSATURATED?

a)b)

c)

d)

SATURATED FATS All C bonded to H No C=C double bonds

long, straight chainmost animal fats solid at room temp.(mostly animal fats)

contributes to cardiovascular disease (atherosclerosis) = plaque deposits

UNSATURATED FATS C=C double bonds in the fatty acids

plant & fish fats vegetable oilsliquid at room

temperaturethe kinks made by double bonded C prevent the molecules from packing tightlytogether

HYDROGENATED FATS (TRANS FATS)

i.e. peanut butter, margarine

unsaturated fats have been synthetically converted to saturated fats by adding hydrogen

prevent lipids from separating out in liquid (oil) form

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STRUCTURE OF PHOSPHOLIPIDS glycerol + 2 fatty acids + PO4

PO4 negatively charged

other small molecules may also be attachedadenine (ATP)

THE ARRANGEMENT OF PHOSPHOLIPIDS IN CELL MEMBRANES

this arrangement occurs spontaneously when added to water

hydrophobic fatty acids meet “tail-to-tail”

hydrophilic head groups interact water

major components of all cell membranes

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PHOSPHOLIPIDS Hydrophobic or hydrophilic?

fatty acid tails = hydrophobicPO4 = hydrophilic headdual “personality”

interaction with H2O is complex& very important!

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PHOSPHOLIPIDS IN WATER Hydrophilic heads attracted to H2O Hydrophobic tails “hide” from H2O

self-assemble into aggregates micelleliposomeearly evolutionary stage of cell?

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WHY IS THIS IMPORTANT? Phospholipids define outside vs. inside Where do we find phospholipids in cells?

cell membranes

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PHOSPHOLIPIDS & CELLS Phospholipids of cell membrane

double layer = bilayerhydrophilic heads on outside

in contact with aqueous solutionhydrophobic tails on inside

form coreforms barrier between cell &

external environment

CHOLESTEROL, A STEROID a molecule from

which other steroids, including the sex hormones are synthesized

contains four fused (interlocking) rings

a common component of animal cell membranes

high levels of it in the blood may contribute to atherosclerosis

2005-2006

DIVERSITY IN STEROIDS

STEROIDS ex: cholesterol, sex hormones 4 fused C rings

different steroids created by attaching different functional groups to rings

cholesterol

FROM CHOLESTEROL SEX HORMONES What a big difference a little atom can make!

CHOLESTEROL Important cell component

animal cell membranes precursor of all other steroids

including vertebrate sex hormones high levels in blood may contribute to

cardiovascular disease

CHOLESTEROLhelps keep cell membranes fluid & flexible

Let’s build some Lipids!