Lipids Flashcards
Describe the test for lipids
The Emulsion Test:
1. Take 2cm3 of the test sample and add 5cm3 of ethanol.
2. Shake the test tube thoroughly to dissolve any liquid in the sample
3. Add 5 cm3 of water and shake gently
If present, a milky white emulsion will form as lipid droplets spread throughout the water (from the carbohydrates.)
Define Emulsion
A fine dispersion of minute droplets of one liquid in another, in which it is not soluble or miscible
Information on Lipids 5
-insoluble in water but soluble and can be dissolved using organic substances e.g., alcohols and acetones
- Good source of energy: provide x2 more the same mass as Carbohydrates as contains lots of carbon and hydrogen bonds.
- Waterproofing in plants and animals: waxy cuticle on leaves and sebaceous fluid on skin
-Good insulating material as poor conductor of heat
-protect soft organs
How do triglycerides form?
Condensation reaction between 3 fatty acids and 1 glycerol molecule forming ester bonds, and releasing 3 water molecules.
Properties of fatty acids
- glycerol same but different fatty acids in lipids: different properties from composition of fatty acids tail
- tails are hydrophobic, making them insoluble
- carbon atom links fatty acid to glycerol
- RCOOHH
Saturates fatty acid chains:
- every Carbon atom is indeed to as many hydrogen atoms. No more can be added
-found in animal fats
-straight carbon chains - pack together to form solids at room temperature
Unsaturated fatty acid chains
- double bonds: kinks in carbon chain
- found in vegetable oils, nuts and fish
- don’t pack together easily so liquids at room temperature
- more double bonds = more kinks
Saturated fats definition
Fats containing high proportion of fatty acid molecules without double bonds.
Unsaturated fats definition:
High proportion of fatty acids with at least one double bond.
Structure and function of triglycerides: 5
- high ratio of energy storing carbon hydrogen bonds (excellent energy source.)
- low mass to energy ratio: lots of energy stored in small mass. Beneficial to animals who need energy store without carrying extra weight.
- insoluble - don’t effect osmosis in cells.
- when oxidised, release water
-thermal insulation
Formation of phospholipids
- a glycerol backbone, a polar hydrophilic phosphate group and hydrophobic fatty acid chains (2)
- condensation reaction between them and forming ester bonds between glycerol and fatty acids
-tails splay outwards: waterproofing and inwards = phospholipid bilayer in membrane.
Similarities of phospholipids and triglycerides: 3
- both formed by condensation reaction with ester bonds.
- glycerol and fatty acid, C and H and O
- Possess hydrophobic properties
-may be attached to unsaturated or saturated fatty acid.
Differences between phospholipids and triglycerides: 4
- T = energy storage when oxidised P = membrane formation
- P = can form bilayer
- T= entirely hydrophobic P = part is hydrophobic and hydrophilic
- T = glycerol and 3 fatty acids. P = glycerol, phosphate group and 2 fatty acids
Are triglycerides and phospholipids polymers?
Macromolecules.
They are not made by a small repeating unit.