section 2: biological molecules - topic 4: lipids Flashcards
what are lipids?
macromolecules.
what do all lipids contain?
carbon.
hydrogen.
oxygen.
what are the 3 types of lipids?
triglycerides.
phospholipids.
cholesterol.
what is the structure of a triglyceride?
they have 1 molecule of glycerol with 3 fatty acids attached to it.
how are triglycerides formed?
they’re synthesised by the formation of an ester bond between each fatty acid and the glycerol molecule.
how many ester bonds does 1 triglyceride molecule have?
3.
how is each ester bond formed?
by a condensation reaction.
what is the process called in which triglycerides are synthesised?
esterification.
how is an ester bond broken?
in a hydrolysis reaction.
what is the structure of fatty acids?
they have long ‘tails’ made of hydrocarbons.
the ‘tails’ are hydrophobic.
the tails make lipids insoluble in water.
all fatty acids have the same basic structure, but the hydrocarbon tail varies.
what are the 2 kinds of fatty acids?
saturated.
unsaturated.
the difference is in their hydrocarbon tails.
what is the stricture of saturated fatty acids?
they don’t have any double bonds between their carbon atoms in their hydrocarbon tails.
what is the structure of unsaturated fatty acids?
they have at least 1 double bond between carbon atoms - causes the chain to kink.
what is the difference between phospholipids and triglycerides?
they are pretty similar, except the 1 of the fatty acid molecules is replaced by a phosphate group.
phosphate group = hydrophilic.
fatty acid tails = hydrophobic.
what is the structure of cholesterol?
has a hydrocarbon ring structure attached to a hydrocarbon tail.
the ring structure has a poly hydroxyl (OH) group attached to it.
what do animals and plants use triglycerides for?
mainly used as energy storage molecules.
what do some bacteria use triglycerides for?
to store both energy and carbon.
why are triglycerides good for storage?
because the long hydrocarbon tails of the fatty acids contain lots of chemical energy.
^ a load of energy is released when they’re broken down.
how are triglycerides insoluble?
they bundle together as insoluble droplets in cells because the fatty acid tails are hydrophobic.
^ the tails face inwards - shielding themselves from water with their glycerol heads.
why is triglycerides being insoluble useful?
because they don’t cause water to enter the cells by osmosis - which would make them swell.
where are phospholipids found?
in the cell membranes of all eukaryotes and prokaryotes.
they make up the phospholipid bilayer.
describe the phospholipid heads & tails.
heads = hydrophilic.
tails = hydrophobic.
what is the function of cholesterol in eukaryotes?
help strengthen the cell membrane by interacting with the phospholipid bilayer.
what is the structure of cholesterol?
has a small size and flattened shape.
^ allows cholesterol to fit in-between the phospholipid molecules in the membrane.
how does cholesterol act upon the membrane?
bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together.
^ this helps to make the membrane less fluid and more rigid.
