Lipids

• Triglycerides have a glycerol and three fatty acids
• fatty acids can be saturated and unsaturated (double bonds)
• Phospholipids have a phosphate, glycerol, two fatty acids. The "head" is hydrophilic and "tail" hydrophobic
• In triglycerides the tail has a long hydrocarbon chain, that contains a lot of chemical energy and a lot of energy is released when they are broken.
• Triglycerides are insoluble, so they don't affect the water potential, so water enters cells through osmosis. They creates insoluble droplets as the tails are hydrophobic and heads are hydrophilic.
• Phospholipids create the bilayer of cell membrane, the centre is hydrophobic so water soluble substances cannot easily pass through, so act as a barrier.
• The emulsion test for lipids, shake the test substance with ethanol and after that add water, a milky emulsion forms if lipids are present. The more lipids present the more milky.