lipids

why are lipids non polar

because elections are evenly distributed

what is the biological roles of lipids

• controlling fluidity of the cell membrane

• electrical insulation

• hormone production

• waterproofing

what are triglycerides made off

one glycerol and 3 fatty acids

what is the general formula of triglycerides

CnH(2n+1)COOH

what’s the function of triglycerides

• energy storage

• thermal insulation (buoyancy, and around vital organs cushioning)

• the long fatty acids chains release lots of energy when broken down.

what is glycerols

a small 3 carbon molecule with three alcohol groups (C3H8O3)

why are triglycerides good for energy store

they yield more energy per unit mass than other compounds so are good for energy storage

properties of fatty acids

1. fatty acids have a carboxyl group and a hydrocarbon chain

2. the chain can be from 14-22 carbon long

3. fatty acids have the same basic structure but the hydrocarbon tail varies

4. the tails are hydrophobic (they repel water molecules) therefore lipids are insoluble

what are saturated fats

• they have no C=C bonds in the chain

• this makes them saturated and straight chains

what are mono saturated fats

• they have one C=C bond in the chain

• this causes a kink and bends in the chain

• bending in the chains means they cannot pack closely together

• this makes them liquid at room temp

what are poly saturated fats

• they have several C=C bonds

• this makes them unsaturated

• this causes kinks and bends in the chain

• the bends lower the melting point

how are triglycerides formed

1. triglycerides are made of one glycerol and 3 fatty acids joined together

2. each hydroxyl group interacts to form an ester bond between the glycerol and each fatty acid

3. during the ester bond formation three water molecules are released

4. this reaction is called esterification

5. when triglycerides are broken down, 3 water molecules are needed to be supplied to reverse the reaction

structure of triglycerides

what are phospholipids

lipids with a phosphate group rather than a fatty acid chain.

what’s the property of the phosphate group in phospholipids?

it’s hydrophilic

what’s micelle

1. when mixed with water, phospholipids form droplet spheres

2. the hydrophilic head gave the water

3. the hydrophobic tails gave each other

4. this is called micelle

what’s a phospholipid bilayer

• Made of phospholipids (hydrophilic heads + hydrophobic tails)

• In water, tails hide from water, heads face water

• Two layers form: tails inside, heads outside → bilayer

• Basis of cell membranes; creates a semi-permeable barrier

what are sterols also known as

steroid alcohols

what are sterols

complex alcohol molecules based on a 4 carbon ring structure with a hydroxyl group at the end of

the hydroxyl group is polar and therefore hydrophilic

the rest of the molecules is hydrophobic

where is cholesterol made

it’s manufactured in the liver and intensifies.

what’s the function of cholesterol

it positions itself between the phospholipids in the membrane,

it adds stability to the membrane (fluid at low temp and not too fluid at high temp)

vitamins D, steroid, hormones and bile at

produced using cholesterol

what’s the steps for the emulsion test for lipids?

lipids do not dissolve in water but they do in ethanol to find out if there is fats in a sample, you do an emulsion test.

1. add ethanol to a test substance and shake throughly for about a minute so it dissolves

2. add water to the solution

3. if lipid is present, it will show as a milky emulsion. The more lipids, the more noticeable the milky colours will be.

4. (the rest can be improved by adding dye Sudan III, which will stain the lipids red)