Zusammenfassung der Ressource
Lipids
- Test for Lipids
- Emulsion Test
- Add ethanol to sample in a test tube
- Shake test tube
- Add to water and any lipid shows as a milky emulsion
- More lipid equals more noticeable milky colour
- Intro
- Main groups are triglycerides and phospholipids
- Insoluble in water
- Soluble in alcohols and acetone
- Triglycerides
- Structure
- Triglycerides are molecule of glycerol and three fatty acids
- Fatty acid "tail" of triglyceride are hydrophobic - repel water molecules
- This makes lipids insoluble in water
- Formation
- Glycerol and fatty acids combine by condensation reactions
- Forms an ester bond
- Hydrolysis therefore produces glycerol and three fatty acids
- Fatty acid chains can be saturated / unsaturated
- Saturated, no double C-C bonds
- Mono-unsaturated, one double bond
- Polyunsaturated, more than one double bond
- Unsaturated causes chain to bend
- Bend in the chain means they can not pack closely together
- Causes them to be liquid at room temp e.g. they are oils
- Function
- Mainly used for energy storage
- Long tails contain many bonds that release chemical energy when broken down
- Contain more energy than carbohydrates
- Phospholipids
- Structure
- Phospholipids similar to triglycerides as one fatty acid is replaced by a phoshate group
- Polar molecule, phosphate end attacts water and fatty acids repel water
- Function
- Forms a bilayer for cell membranes forming a hydrophobic barrier between outside and inside a cell
- Water soluble substances cant pass through
- Helps form glycolipids by combining phosphate group on membrane with carbs
- Important for cell recognition