Chapter 3 - Biological molecules - lipids Flashcards
what are the two main types of lipids
fats and oils
what elements do lipids contain
hydrogen carbon oxygen
why do oil and water not mix
lipids are non polar meaning they cannot form hydrogen bonds with water
what is a triglyceride
one glycerol molecule and three fatty acids
what is the structure of a fatty acid
carboxyl group (COOH) and a hydrocarbon chain
how do the glycerol and fatty acids interact
they both have hydroxyl groups which interact to form ester bonds (esterification)
what is the difference between saturated and unsaturated fatty acids
when there are no double bonds between any of the carbon atoms in the chain it is saturated. if there is just one double bond it is monounsaturated and if there is more than one double bond it is polyunsaturated
is fat or oil unsaturated
oil
what are phospholipids
modified triglycerides which also contain phosphorus
how does the structure of a phospholipid differ from a triglyceride
one of the fatty acids is replaced by a phosphate
how does a phospholipid interact with water
it has a hydrophobic tail and a hydrophilic head so the heads stay in the water and the tail stick out - they are surfactants. they form the basis of the cell membrane
what are sterols
steroid alcohols - another type of lipid that isn’t fat or oil - they are complex alcohol molecules that have dual hydrophilic/hydrophobic properties - the hydroxyl group is polar and hydrophilic and the rest of the molecule is hydrophobic
what is the role of cholesterol
it is a sterol that adds stability to cell membranes by regulating fluidity
what is the test for lipids
the emulsion test - the sample is mixed with ethanol and then mixed with water and shaken. If a white emulsion forms a layer on top of the solution this indicates the presence of a lipid
