Lipids AP Biology 2006-2007

Lipids

Lipids Lipids are composed of C, H, O Major Types of Lipids _______________________ (H-C) Major Types of Lipids ______ and ______ ______________ ___________ __________ Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

Functions of Lipids ________________ ______________ body organs Think ________ _______________ Think duck feathers Cell-to-cell communication Think _________ Formation of cell ________________

Basic Structure of Lipids Do _____ form “polymers” exactly Not big molecules made of smaller subunits not a “choo-choo train” of monomers Mostly long chains of carbon and hydrogen atoms stuck to a “hook”…. _______ = the hook

dehydration synthesis Fats and oils Structure: ____________ (3C alcohol) + _____________ fatty acid = ___________ _____ “tail” with carboxyl (COOH) group “head” enzyme Look at structure… What makes them hydrophobic? Note functional group = carboxyl H2O dehydration synthesis

Building Fats _________________ ____ fatty acids linked to glycerol ________ linkage = between OH & COOH hydroxyl carboxyl Yet Another type of ________ bond BIG FAT molecule!!

Dehydration synthesis H2O ___________ synthesis enzyme H2O Pulling the water out to free up the bond enzyme H2O enzyme H2O

Why do humans like fatty foods? very evenly – no polarity Fats store energy Long HC chain polar or non-polar? hydrophilic or hydrophobic? Function: energy ____________ concentrated all ______ Bonds ___x energy of carbohydrates C and H share electrons very evenly – no polarity results. What happens when you add oil to water Why is there a lot of energy stored in fats? • big molecule • lots of bonds of stored energy So why are we attracted to eating fat? Think about our ancestors on the Serengeti Plain & during the Ice Age. Was eating fat an advantage?

Why is Fat the preferred energy storage molecule of animals Why is Fat the preferred energy storage molecule of animals? (as opposed to starch) More ________ Bonds than in carbs…Remember the Glucose molecule:

C O C C C C 5' 4' 1' 3' 2' CH2OH 6' H OH H OH H H OH H OH Where’s the energy? CH2OH 6' C O In the C-H BONDS!! 5' H OH H C C 4' 1' OH H H OH C C 3' 2' H OH

In lipids there are even MORE C-H bonds than in carbs! Thus, ________ energy packed in a lipid per unit mass _______ as much as in a carbohydrate! ALL ________!!!

Saturated vs. Unsaturated Fats Remember that covalent bonds can be Single, double, or triple In Fatty acids, generally the covalent bonds between the carbons are _____________ However, sometimes a ____________ bond can exist between carbons A DOUBLE bond can cause __________ in the carbon chain.

Saturated fats This means that all the carbons are _______________ with __________________! This means each carbon is holding as many hydrogens as it possibly can (__ H’s per C) ___ C=C double bonds This results in long, ______________ chains These can pack ___________together ______at room temp. _____________ fats, typically Butter, lard Mostly animal fats

Unsaturated fats C=C double bonds in the fatty acids Called ___saturated because the carbons are ____ holding hands with as many hydrogens as possible C=C double bonds cause the fatty acid to ________ ______ at room temperature the kinks made by double bonded C ____________the molecules from packing tightly together plant & fish fats vegetable ________ Mostly plant lipids Think about “natural” peanut butter: Lots of unsaturated fats Oil separates out Companies want to make their product easier to use: Stop the oil from separating Keep oil solid at room temp. Hydrogenate it = chemically alter to saturate it Affect nutrition?

Saturated vs. unsaturated ___________ __________

It’s just like a penguin… ________ Phospholipids Often drawn Like this Structure: glycerol + ___ fatty acids + ______ PO4 = _________ group PO4 = ___________ charged __________ It’s just like a penguin… A head at one end & a tail at the other!

Phospholipids Hydrophobic or hydrophilic? fatty acid tails = PO4 head = split “personality” ___________ ___________ _________- __________ “attracted to water” Come here, No, go away! interaction with H2O is complex & very important! “repelled by water”

Phospholipids in water Hydrophilic heads “_________” to H2O Hydrophobic tails “_______” from H2O can ______-assemble into “bubbles” bubble = “micelle” can also form a ______________________ “bubbles” of phospholipids an early evolutionary step for cells? water bilayer water

Phospholipids & cells Phospholipids of cell membrane double layer = _____layer hydrophilic heads on _____________ in contact with aqueous solution outside of cell and inside of cell hydrophobic tails on ______________ form _______ Phospholipid bilayer Note other molecules in membrane…

Why is this important? Phospholipids create a __________ in water define outside vs. inside they make ______________________! Tell them about soap!

Steroids Structure: ____ fused C ___________ + ?? different steroids created by attaching different _________________________ to rings different _____________creates different _________________ examples: ___________________________ cholesterol

Cholesterol Important cell component animal cell ____________________ ____________ of ____ other steroids including vertebrate ______ hormones high levels in blood may contribute to cardiovascular disease

Cholesterol Important component of cell membrane helps keep cell membranes _________ yet ________

From Cholesterol  Sex Hormones What a big difference a few atoms can make! Same C skeleton, different functional groups

Any Questions? 2006-2007