1. LIPIDS

2. Lipids Lipids have 3 main functions - Energy storage
- Structural component of membranes
- Specific biological functions (chemical signals)
Contain Carbon, Hydrogen & Oxygen (same as carbohydrates but with less oxygen)
Insoluble in water (soluble in non-polar solvents)
Lipids are NON-POLAR

3. Saturated and Unsaturated Fat
SATURATED FATTY ACIDS – No double bonds between carbons
Can be packaged close together
Melt at HIGHER temperatures
More dense
Eg. Butter (solid at room temp.)
UNSATURATED FATTY ACIDS – contain double bonds between carbons
Double bonds produce ‘BENDS’ in the
molecule (see above)
Less dense
Cannot be packed as closely together
Melt at lower temperatures
Eg. Corn oil (liquid at room temp.)
VIDEO: Saturated & Unsaturated Fatty Acids

4. Triglycerides Eg. The fats and oils of plants and animals
FATTY ACIDS: long hydrocarbon chain with a carboxyl group
GLYCEROL: 3 Carbons + 3 Hydroxyl groups (alcohol)
GLYCEROL FATTY ACIDS
Condensation reactions occur between the hydroxyl groups on the glycerol and the carboxyl group on each of the 3 fatty acids
Releases water, requires and stores energy in the bond
These bonds are known as
ESTER BONDS
(red in the above diagram)

5. Phospholipids Eg. Cell Membranes
Similar structure to a triglyceride but contain a phosphate group in place of the 3rd fatty acid (SEE DIAGRAM ON RIGHT)
Spontaneously form a bilayer in a watery environment
Polar and Non-Polar ends
Polar molecules don’t mix with non-polar molecules (oil + water)
Polar and polar do mix (salt + water)
SEE PHOSPHOLIPID BILAYER AND THE FLUID MOSAIC MODEL
HYDROPHILIC
HYDROPHOBIC

6. Steroids Eg. Testosterone, Oestrogen, Aldosterone
Structure very different to other lipids
Have a backbone of 4 Carbon rings
(3 rings with 6 carbons/ 1 ring with 5)
CHOLESTEROL: is the pre-cursor of several steroids, including hormones. It is also an important component of cell membranes. Cholesterol is NOT a steroid itself. (SEE DIAGRAM ON THE RIGHT)
WAXES Eg. Plant covering on leaves, animal ears
Waxes also contain ester linkages but each molecule contains only one fatty acid sub-unit
This is linked to a molecule of a long chain alcohol instead of glycerol