lipids Flashcards
what do all lipids contain
hydrocarbons
what are the two types of lipids
triglycerides and phospholipids
what does a triglyceride contain
one molecule of glycerol, three fatty acid molecules made of hydrocarbons
describe the ‘tails’ in triglycerides
they are hydrophobic, they repel water molecules
why are lipids insoluble in water
due to their hydrophobic tails
what are the two types of fatty acids
saturated and unsaturated
what’s the difference between saturated fatty acids and unsaturated fatty acids
saturated fatty acids don’t have any double bonds whereas unsaturated fatty acids do have double bonds
what causes the unsaturated fatty acid chain to kink
the double bonds
how are triglycerides formed
by a condensation reaction
what bonds are between fatty acids and glycerol
ester bonds
what does a phospholipid contain
one phosphate group, one glycerol molecule and two fatty acids
what are triglycerides mainly used as and why
energy storage molecules, because the long hydrocarbon tail contains lots of chemical energy and a lot of energy is released when they are broken down
what are a bundle of triglycerides called
droplets
what is the structure of a triglyceride droplet
the tails face inside shielding themselves from the water with the glycerol head
what do phospholipids make
the bilayer of cell membranes
what does a cell membrane do
controls what enters and leaves a cell
do the heads (in a lipid) like water or not? what is the name
they like water so are hydrophilic
describe the structure of a phospholipid bilayer
a double layer with heads facing out towards the water on each side. the centre is hydrophobic
the centre of a phospholipid bilayer is hydrophobic, what does this mean
water soluble substances can’t easily pass through it
what is the test for lipids
the emulsion test
explain what happens in the emulsion test
shake the test substance with ethanol for about a minute, then pour the solution into water. any lipid will show up as a milky emulsion
if there is lipid present in the emulsion test what will it look like
a milky white emulsion on the top of the water
give two reasons why triglycerides are used as an energy storage
they’re insoluble in water and contain lots f chemical energy
