Lipids: Fats & Oils & Wax & Steroid

Lipids Lipids are composed of C, H, O 4 groups: Do not form polymers fats oils waxes steroids Do not form polymers big molecules made of smaller subunits not a continuing chain Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

Lipids Six functions of lipids: 1. Long term energy storage 2. Protection against heat loss (insulation) 3. Protection against physical shock 4. Protection against water loss 5. Chemical messengers (hormones) 6. Major component of membranes (phospholipids) Made of same elements as carbohydrates but very different structure/ proportions & therefore very different biological properties

Why do humans like fatty foods? Fats store energy Function: energy storage 2x energy of carbohydrates cushion organs insulates body think whale blubber! 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?

dehydration synthesis Fat subunits Structure: glycerol (3C alcohol) + fatty acid fatty acid = long “tail” with COOH group at “head” Look at structure… What makes them hydrophobic? Note functional group = carboxyl dehydration synthesis

Fatty Acid Structure Carboxyl group (COOH) forms the acid. “R” group is a hydrocarbon chain (chain of hydrogens and carbons).

A Representative Fatty Acid Carboxyl Group Hydrocarbon Group

Synthesis of a Fat

A Phospholipid

Hydrophilic vs hydrophobic Hydrophilic – Water loving – soluble in water Hydrophobic – water hating – is NOT soluble in water Triglyceride =1 glycerol, 3 fatty acids Hydrophilic Phospholipids = 1 glycerol, 2 fatty acids 1 phosphate group tails are hydrophobic the heads are hydrophilic. make up cell membranes

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

Unsaturated Fatty Acid Saturated Fatty Acid

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

Saturated vs. unsaturated 

If fatty acids are unsaturated, their shape is altered from a saturated molecule so the molecules in the Lipid push apart, thus making it more fluid and oily. Animals tend to have more saturated, and consequently solid at room temperature lipids whereas plants tend to have more unsaturated and so fluid at room temperature lipids

Waxes Ear wax – protection from foreign materials/ invaders (such as insects) Wax coating on leaves – forms a barrier to keep water in leaves

Steroids Cholesterol Hormones (chemical messengers) Found in cell membranes – keeps them flexible Hormones (chemical messengers)

Quiz What are the four types of lipids ? Name as many functions of lipids as possible (6). What is the difference in saturated & unsaturated ? How could you tell the difference in saturated & unsaturated by looking at an item ? What is healthier, saturated or unsaturated fats ? Lipids contain more energy than carbs, so why are carbs are primary energy source ? What is the monomer & polymer of lipids ? Structurally, how do you tell the difference in carbs & lipids ?

Answers Fats, oils, waxes, & steroids Energy storage, insulation, protection from water loss, protection against physical shocks, chemical messengers, component of cell membranes C=C double bonds are in unsaturated Saturated are solid at room temp., unsaturated are liquid at room temp. unsaturated Lipids are harder to break down, because they are insoluble in water Technically, there are not monomers & polymers Both contain C,H, & O, but in carbs they are in a 1:2:1 ratio