• Composed of C, H and O (fewer polar OH bonds than carbohydrates)
• Can be used at energy storage, components of cell membranes, chemical signals & thermal insulation
  • Are a more efficient energy source then carbohydrates
• 4 families à fats (triglycerides), phospholipids, steroids & waxes

Triglycerides

Triglycerides - An ester of 3 fatty acids + a glycerol molecule
Glycerol - a 3 carbon alcohol with 3 hydroxyl groups
Fatty Acid - a long-chain carboxylic acid

• Fatty acids can be saturated of unsaturated and usually even numbered (16 or 18)
  • Saturated -> In animals                                                                                                                                                 Long straight chains and can rotate freely on the glycerol backbone

                      Can be packed tightly together à solids

               o  Unsaturated ->in plants

                        Cannot rotate freely and have kinks in their chain (due to 'cis' & 'trans' shapes from the double bond)

                        Cannot be packed closer together à liquids

Phospholipids

• Glycerol + 2 fatty acids
• Has hydrophobic tails and a hydrophilic head

Steroids

• Hydrophobic molecules with 4 fused hydrocarbon rings (e.g. cholesterol, vitamin D, bile salts)

Waxes

• Lipids containing long chain fatty acids linked to alcohols or carbon rings
• Hydrophobic