Lipids, triglycerides and emulsion test Flashcards
what do all lipids have
contain carbon hydrogen and oxygen
soluble in acetone and alcohol
what are the main groups of lipids
triglycerides and phospholipids
what are the roles of lipids
insulation protection cell membranes source of energy waterproofing
how do lipids provide a source of energy
when oxidised lipids provide more than twice the energy of the same carbohydrate and release valuable water
how do lipids provide waterproof
they are insoluble in water, therefore they are valuable in waterproofing
how do lipids provide insualtion
fats are slow conductors of heat and when stored beneath the surface of the body they help to retain heat
how do lipids contribute to cell membranes
phospholipids contribute to flexibility of cell membrane and transfer of lipid soluble substances across them
what are triglycerides made of
3 fatty acids and one glycerol molecule
how are triglycerides formed
fatty acids form esther bonds with glycerol to make triglycerides via a condensation reaction
what does hydrolysis of triglycerides produce
glycerol and three fatty acid molecules
what do all fatty acid chains contain
COOH group and OH attached
what is a saturated molecule
when there is no double carbon bond
what is the shape and state of a saturated fat at room temperature
straight chain and solid
what is an unsaturated molecule
double carbon bond present
what is the shape and state of unsaturated molecules
double bond causes kinks in structure. kinks mean fatty acids unable to closely pack together so it is liquid at room temp
how does the structure of triglycerides mean that it is a good source of water
high ratio of hydrogen to oxygen atoms means triglycerides release water when oxidised
how does the structure of triglycerides make it a good storage molecule
low mass to energy ratio means alot of energy can be stored in a small volume
how does the structure of triglycerides make it an excellent source of energy
high ratio of energy storing carbon-hydrogen bonds to carbon atoms
how are phospholipids different to triglycerides
one fatty acid is replaced with a phosphate molecule
what are phospholipids made of
hydrophobic head
hydrophillic tail
how does the hydrophobic head behave
attracted to water so interacts with it
how do the hydrophillic tails behave
repels water so orientates itself readily away from water but mixes with fat
how does the structure of phospholipids relate to its function
hydrophillic head helps to hold at the surface of the cell membrane
phospholipid structure allows them to form glycolipids by combining with carbohydrates at the cell surface membrane. Glycolipids are important in cell recogniition.
polar molecule of hydrophillic head and two fatty acid tails means when in an aqueous environment phospholipids form a bilayer within cell surface membrane and therefore hydrophobic barrier is formed inside and outside of cell
describe the emulsion test
- take a completely dry and grease free tube
- to 2cm^3 of sample being tested add 5cm^3 of ethanol
- shake the tube thoroughly to dissolve any lipid in sample
- add 5cm^3 of water and shake gently
- A milky white solution indicates the presence of a lipid
- as a control repeat the procedure with water instead of sample and the final solution should remain clear
why does solution turn cloudy when lipids are present
cloudy colour due to lipids being finely dispersed in solution to form an emulsion. light passing through this is refracted from water droplets to oil droplets making the solution appear cloudy
