lipids Flashcards
what is a triglyceride?
● a lipid
● one molecule of glycerol with 3 fatty acids attached to it
why do fatty acid molecules have long tails made of hydrocarbons?
●tails are hydrophobic (repel water molecules)
●tails make lipids insoluble in water
●fatty acids have same base structure but hydrocarbon tail varies
what reaction are triglycerides formed by?
● condensation reaction
● when ester bond formed between fatty acid and glycerol a molecule of water is released
what are the 2 kinds of fatty acids?
● saturated
● unsaturated
saturated fatty acids don’t have any
double bonds between their carbon atoms
the fatty acid is saturated with hydrogen
unsaturated fatty acids have at least
one double bond between carbon atoms, which causes the chain to kink
what is a phospholipid?
● lipids found in cell membranes
● make up the bilayer of cell membranes
● similar to triglycerides except one of the fatty acid molecules is replaced by a phosphate group
● phosphate group is hydrophilic (attracts water)
● fatty acid tails are hydrophobic (repel water)
how does the structure of triglycerides relate to their function?
● long hydrocarbon tails of fatty acids contain lots of chemical energy
● insoluble - doesn’t affect water potential of cell and cause water to enter cell by osmosis
● triglycerides clump together as insoluble droplets in cells as fatty acid tails are hydrophobic tails face inwards, shielding themselves from water with glycerol heads
how does the structure of phospholipids relate to their function?
● heads are hydrophilic and tails are hydrophobic
● so they form double layer with heads facing out on each side
● centre of bilayer is hydrophobic so water soluble substances can’t easily pass through it
● membrane acts as barrier
how do you test for lipids?
emulsion test
what is the emulsion test?
● crush sample
● add ethanol
● pour into water
● any lipid will show up as milky emulsion
● more lipid there is the more noticeable milky colour will be
what does monounsaturated mean?
1 double bond
what does polyunsaturated mean?
multiple double bonds
