Lipids energy storage AP Biology 2006 2007 LIPIDS

Lipids energy storage AP Biology 2006 -2007

LIPIDS Elements § Carbon § Hydrogen § Oxygen § (no ratio) Fatty acids are hydrophobic: hydrophobic they repel water. (can be amphipathic) AP Biology Subunit § 1 glycerol § 3 fatty acids

1 2 3 4 5 AP Biology Know These functional groups!

LIPIDS examples § Fats, oils, waxes § Myelin sheath § Cell membrane § Steroid hormones AP Biology

Lipids § Lipids are composed of C, H, O u long hydrocarbon chain § Diverse group fats u phospholipids u steroids u § Do not form polymers big molecules made of smaller subunits u not a continuing chain u AP Biology

Remember: HO HO HO, we’re GLad Santa is coming! AP Biology

Fat subunits § Structure: u glycerol (3 C alcohol) + fatty acid § fatty acid = long HC “tail” with COOH group at “head” enzyme dehydration synthesis AP Biology

Building Fats § Triacylglycerol 3 fatty acids linked to glycerol u ester linkage = between OH & COOH u AP Biology

Dehydration synthesis dehydration synthesis enzyme AP Biology enzyme

Fats store energy § Long HC chain Why do humans like fatty foods? polar or non-polar? u hydrophilic or hydrophobic? u § Function: u energy storage § very rich § 2 x carbohydrates cushion organs u insulates body u § think whale blubber! AP Biology

Fat Saturation (ewww. . . gross!) Saturation means “full”, so what could they be full of? H Full of atoms! And wherever there is a chemical bond, there is stored energy. AP Biology

Saturated fats § All C bonded to H § No C=C double bonds long, straight chain u most animal fats u solid at room temp. u § contributes to cardiovascular disease (atherosclerosis) = plaque deposits AP Biology

Unsaturated fats § C=C double bonds in the fatty acids plant & fish fats u vegetable oils u liquid at room temperature u § the kinks made by double bonded C prevent the molecules from packing tightly together AP Biology mono-unsaturated? poly-unsaturated?

Saturated vs. unsaturated AP Biology

So limit your intake of FAT, eat polyunsaturated fat (why? ) and avoid transfat. Basically, trans fat is made when manufacturers add hydrogen to vegetable oil-a process called hydrogenation. Hydrogenation increases the shelf life and flavor stability of foods containing these fats. And raises your LDL cholesterol level putting you at greater risk for heart disease!

Ester linkage Triacyl glycerols =triglycerides, they remove the hydrophillic portion of carboxyl (-COOH) AP Biology

Major Function of Fats § Energy storage: in adipose § tissue for humans and other mammals 2 X’s as much energy as carbs. § OTHER FUNCTIONS: -cushions vital organs (ex. kidney) -buoyancy -insulates body (ex. polar bear) -waxes AP Biology (waterproof protection)

Human adipose cells swollen with fat!!!!! Humans can grow more fat cells, but can never get rid of them!! As we gain and lose weight, they just swell and shrink. …Makes you think twice about those French fries!!!

Advantage of Carbohydrates for Energy Storage § Carbohydrates are more easily § digested than lipids- so stored energy can be released more RAPIDLY Carbohydrates are soluble in water, so they are easier to transport to and from storage sites AP Biology

Advantage of Lipids for Energy Storage § Lipids contain MORE § ENERGY per gram than carbs, so stores of lipids are lighter Lipids are insoluble in water, they do not cause problems with osmosis in the cell AP Biology

Advantage of Carbohydrates for Energy Storage § Carbohydrates are more easily § digested than lipids- so stored energy can be released more RAPIDLY Carbohydrates are soluble in water, so they are easier to transport to and from storage sites AP Biology

Phospholipids § Structure: u glycerol + 2 fatty acids + PO 4 § PO 4 negatively charged It’s just like a penguin… A head at one end & a tail at the other! AP Biology

Phospholipids § Hydrophobic or hydrophilic? fatty acid tails = hydrophobic u PO 4 = hydrophilic head u dual “personality” u It likes water & also pushes it away! interaction with H 2 O is complex & very important! AP Biology

Phospholipids in water § Hydrophilic heads attracted to H 2 O § Hydrophobic tails “hide” from H 2 O u can self-assemble into “bubbles” § bubble = “micelle” § can also form bilayer § early evolutionary stage of cell? bilayer AP Biology

Why is this important? § Phospholipids create a barrier in water define outside vs. inside u cell membranes u AP Biology

Phospholipids & cells § Phospholipids of cell membrane u u double layer = bilayer hydrophilic heads on outside § in contact with aqueous solution outside of cell and inside of cell u hydrophobic tails on inside § form core u forms barrier between cell & external environment Tell them about soap! AP Biology

Steroids § ex: cholesterol, sex hormones § 4 fused C rings u different steroids created by attaching different functional groups to rings cholesterol Steroid abuse link AP Biology

Cholesterol § Important cell component animal cell membranes u precursor of all other steroids u § including vertebrate sex hormones u AP Biology high levels in blood may contribute to cardiovascular disease

Cholesterol Important component of cell membrane helps keep cell membranes fluid & flexible AP Biology

From Cholesterol Sex Hormones § What a big difference a few atoms can make! AP Biology