1.3 Lipids Flashcards
name two groups of lipid
-triglycerides
-phospholipids
describe the structure of a fatty acid (RCOOH)
-variable R-group - hydrocarbon chain (this may be saturated or unsaturated)
- -COOH = carboxyl group
describe saturated fatty acids
- no C=C double bonds in hydrocarbon chain → all carbons fully saturated with hydrogen
describe unsaturated fatty acids
-unsaturated - one or more C=C double bond in hydrocarbon chain (creating a bend / kink)
describe how triglycerides form
-1 glycerol molecule and 3 fatty acids
-3 condensation reactions
-removing 3 water molecules
-forming 3 ester bonds
explain how the properties of triglycerides are related to their structure
function: energy storage
● high ratio of C-H bonds to carbon atoms in hydrocarbon chain
○ so used in respiration to release more energy than the same mass of carbohydrates
● hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards)
○ so no effect on water potential of cell (or can be used for waterproofing)
describe the difference between the structure
of triglycerides and phospholipids
-one of the fatty acids of a triglyceride is substituted by a phosphate-containing group
describe how the properties of
phospholipids relate to their structure
● phosphate heads are hydrophilic
○ attracted to water so point to water (aqueous environment) either side of membrane
● fatty acid tails are hydrophobic
○ repelled by water so point away from water / to interior of membrane
function of triglycerides
-energy storage
function of phospholipids
-form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances
describe the test for lipids
- add ethanol, shake (to dissolve lipids), then add water
- positive result = milky white emulsion
