What are lipids?
a mixed group of hydrophobic compounds composed of the elements carbon, hydrogen and oxygen
How are triglycerides formed?
the condensation of one molecule of glycerol and 3 molecules of fatty acid
What kind of bond is formed by rection between glycerol and fatty acid?
ester bond
What is a saturated fatty acid?
the hydrocarbon chain has only single bonds between carbons
What is a unsaturated fatty acid?
hydrocarbon chain has at least one double bond between carbons
What are the properties of triglycerides?
How does structure relate to function?
- energy storage molecule, insulation, protection in fatty tissue under skin or surrounding organs
- the long hydrocarbon tails of the fatty acids contain lots of chemical energy so lots of energy is released when they’re broken down and due to large energy storing carbon-hydrogen bonds compared to number of carbon atoms
- insoluble in water so they don’t affect the water potential so the cell cant swell by osmosis
- triglycerides bundle together as insoluble droplets - hydrophobic fatty acid tails inwards
- containing saturated fatty acids = high melting points - warm blooded animals - solid at room temp
- containing unsaturated fatty acids = low melting points = cold blooded animals - liquid at room temp
- lipids have a low mass = can be stored without increasing the mass and preventing movement
- act as a metabolic water source = can release water if oxidised
How do triglycerides differ to phospholipids?
same structure but phospholipids have a phosphate group in place of a fatty acid chain
What are the properties of phospholipids?
- phosphate group is hydrophilic
- fatty acid tails hydrophobic
- when mixed with water phospholipids form droplet spheres with hydrophilic heads facing water and hydrophobic tails facing eachother (a micelle)
- form cell membrane bilayer = controls what enters and leaves - hydrophilic heads facing water hydrophobic tails facing inwards so water soluble substances cant easily pass through (membrane acts as a barrier)
- more unsaturated fatty acid tails = fluid membrane
What is the test for lipids?
- emulsion test
- add sample and ethanol to test tube and shake for about one minute to dissolve
- add water and shake gently
- any lipid will show up as a milky emulsion
- more lipid = more noticeable milky colour
