Lipids - triglycerides Flashcards
what are lipids
commonly known as fats and oils. these contain the elements hydrogen, oxygen and carbon
what is the difference between fats and oils
lipids that are solid at room temperature are fats
lipids that are liquid at room temperature are oils
are lipids soluble or insoluble in water
insoluble
why are lipids insoluble
they are non polar molecules as the electrons in the outer orbitals that form the bonds are more evenly distributed than in polar molecules. this means there are no positive or negative areas within the molecules so do not attract water molecules
what substance does lipid dissolve in
alcohol
are lipids polymers
no. they are large, complex molecules called macromolecules
why don’t lipids form polymers
lipids aren’t built from repeating units or monomers
what is a triglyceride
made by combining one glycerol molecule with three fatty acids.
what group of chemicals does glycerol belong to
alcohols.
what group of acids do fatty acids belong to
carboxylic acids
what do fatty acids consist of
a carboxyl group (COOH) with a hydrocarbon chain attached.
describe glycerol
has 3 carbon atoms. it is an alcohol so has free -OH groups. it has 3 -OH groups which are important to the structure of triglycerides
describe a fatty acid
have a carboxyl on one end, attached to a hydrocarbon tail, made of only carbon and hydrogen atoms.
how many carbons can fatty acids have
anything from 2 to 20 carbons long
why is the fatty acid an acid
the carboxyl group ionises into H+ and -COO group. this structure is therefore an acid because it produces free H+ ions
what are saturated fatty acids
fatty acid chains that have no double bonds present between the carbon atoms. they are saturated because all the carbon atoms form the maximum number of bonds with hydrogen atoms
what are unsaturated fatty acids
a fatty acid with double bonds between some of the carbon atoms
if there is one double bond present it means..
it is a monounsaturated fatty acid
if there is two or more double bonds it means..
it is a polyunsaturated fatty acid
what does the presence of the double bond in the fatty acid do
causes the molecule to kink or bend and they therefore cannot pack closely together. this makes them liquid at room temperature
why are plants more healthier
they contain unsaturated triglycerides which normally occur as oils and tend to be more healthy than the triglycerides in fats (solids).
what can excess saturated fats cause
coronary heart disease. an excess of any type of fat can lead to obesity
what does a triglyceride consist of
one glycerol molecule bonded to three fatty acids
what do both fatty acids and glycerol molecules have
hydroxyl groups
how do triglycerides form
both fatty acids and a glycerol molecule have hydroxyl group. when these groups react it leads to the formation of three water molecules and bonds between the fatty acids and glycerol molecules
what bond form when glycerol and fatty acids react
ester bonds
what type of bond is an ester bond
covalent
what type of reaction occurs when a triglyceride is formed
esterification/condensation
what needs to be supplied to break down triglycerides
three water molecules
what type of reaction occurs when triglycerides are broken down
hydrolysis
what are the functions of triglycerides
- energy source
- energy store
- insulation
- buoyancy
- protection
- steroid hormones
- cell structure
how are triglycerides used as a source of energy
triglycerides can be broken in respiration to release energy and generate ATP. the ester bonds are hydrolysed and then the glycerol and fatty acids can be broken down completely to carbon dioxide and water. respiration of a lipid produces more water than respiration of sugar
how are triglycerides used as an energy store
insoluble in water so can be stored without affecting the water potential of cells. one g of fat releases twice as much energy as 1g of glucose. this is because lipids have a higher proportion of hydrogen atoms than carbohydrates and almost no oxygen atoms.
how are triglycerides used as a form of insulation
adipose tissue is a storage location for lipids in whales acting as a heat insulator. lipids in nerve cells act as electrical insulators
how are triglycerides used to provide buoyancy
fat is less dense than water so is used by aquatic animals to help them stay afloat
how do triglycerides provide protection
humans have fat around delicate organs as the kidneys
