3.5 Lipids
First review @September 14, 2023
Practise Q's Done
Second review @September 18, 2023
lipids (fats and oils) contain carbon, hydrogen and oxygen
fats are lipids that are solid at room temperature and oils are lipids that are liquids at
room temperature
lipids are not polar molecules because the shared electrons are more evenly distributed
compared to polar molecules such as water
this means that there are no positive or negative regions in lipid molecules meaning
that lipids are insoluble in water— hydrogen bonds unable to form between lipids
and water molecules
lipids have large complex structures and are known as macromolecules, these are built
from repeating units
e.g. triglycerides, phospholipids and sterols
Triglycerides
made by combining a glycerol molecule with three fatty acids
because glycerol is an alcohol and fatty acids are carboxylic acids, they are joined by
condensation polymerisation and form an ester link/ bond — this reaction can also
be called esterification
3.5 Lipids 1
, in order to break triglycerides down, three water molecules need to be supplied to each
triglyceride, since three water molecules are lost during their formation— this is called
hydrolysis
Saturated and Unsaturated
lipids that have no double bonds between carbon atoms are saturated
this means that they can’t react since all the carbon atoms have 4 single bonds
(except the COOH functional group)
lipids that contain a double bond between two carbon atoms are unsaturated
this means that the lipids can still react since there are double bonds ready to be
broken between carbon atoms and react
there are two types of unsaturated lipids
monounsaturated— just one double bond present between two carbon atoms
polyunsaturated— more than one double bond present between pairs of carbon
atoms
the double bonds present in mono and polyunsaturated lipids causes them to have a slight
bend, this means they cannot pack together so closely and are liquids at room
temperature
for this reason, unsaturated lipids are described as oils not fats
unsaturated triglycerides tend to be healthier than saturated triglycerides
3.5 Lipids 2
First review @September 14, 2023
Practise Q's Done
Second review @September 18, 2023
lipids (fats and oils) contain carbon, hydrogen and oxygen
fats are lipids that are solid at room temperature and oils are lipids that are liquids at
room temperature
lipids are not polar molecules because the shared electrons are more evenly distributed
compared to polar molecules such as water
this means that there are no positive or negative regions in lipid molecules meaning
that lipids are insoluble in water— hydrogen bonds unable to form between lipids
and water molecules
lipids have large complex structures and are known as macromolecules, these are built
from repeating units
e.g. triglycerides, phospholipids and sterols
Triglycerides
made by combining a glycerol molecule with three fatty acids
because glycerol is an alcohol and fatty acids are carboxylic acids, they are joined by
condensation polymerisation and form an ester link/ bond — this reaction can also
be called esterification
3.5 Lipids 1
, in order to break triglycerides down, three water molecules need to be supplied to each
triglyceride, since three water molecules are lost during their formation— this is called
hydrolysis
Saturated and Unsaturated
lipids that have no double bonds between carbon atoms are saturated
this means that they can’t react since all the carbon atoms have 4 single bonds
(except the COOH functional group)
lipids that contain a double bond between two carbon atoms are unsaturated
this means that the lipids can still react since there are double bonds ready to be
broken between carbon atoms and react
there are two types of unsaturated lipids
monounsaturated— just one double bond present between two carbon atoms
polyunsaturated— more than one double bond present between pairs of carbon
atoms
the double bonds present in mono and polyunsaturated lipids causes them to have a slight
bend, this means they cannot pack together so closely and are liquids at room
temperature
for this reason, unsaturated lipids are described as oils not fats
unsaturated triglycerides tend to be healthier than saturated triglycerides
3.5 Lipids 2
