Topic 1.3 - Lipids Flashcards
Two types of lipids
Triglycerides
Phospholipids
R group
Can be saturated or unsaturated
Describe the structure of a triglyceride
One molecule of glycerol and three molecules of fatty acid
2) How is a triglyceride formed?
A condensation reaction between glycerol and 3 fatty acids (RCOOH), with the elimination of 3
molecules of water and the formation of 3 ester bonds
Describe the structure and how it relates to the properties of a triglyceride
Non-polar structure (cannot form hydrogen bonds with water molecules) → Not water soluble (so doesn’t
affect water potential) and waterproof.
High proportion of C-H bonds → Good store of energy
5)Describe the structure of a phospholipid
It is made of 1 glycerol molecule, 1 phosphate group and 2 fatty acid chains
6) Is a triglyceride a polymer? Is a phospholipid a polymer?
Polymers are molecules made from a large number of monomers joined together with chemical bonds, so
neither molecules are polymers.
In terms of structure, explain the difference between a phospholipid and a triglyceride
*
Triglycerides have 3 fatty acids, whereas phospholipids have 2 fatty acids.
* Triglycerides have 3 ester bonds, whereas phospholipids have 2 ester bonds.
* Phospholipids have 1 phosphate group, whereas triglycerides do not have a phosphate group
Describe how Phospholipids can arrange themselves to form a cell membrane..
- The plasma membrane is a phospholipid bilayer.
- With hydrophilic
phosphate heads on the outside of the bilayer and hydrophobic fatty
acid tails on the inside of the bilayer. - Hydrophilic/ phosphate group
attracts water to either side of the bilayer
Unsaturated R group
At least one double bond between
carbon atoms in the fatty acid chain
Saturated in R group
ONLY single bonds between carbon
atoms in the fatty acid chain (no C=C
bonds)
Describe the test for lipids
-Crush/grind the food
● Add ethanol
● Then add water and shake/mix
● If it forms a WHITE EMULSION this means that lipids are present
Structure of unsaturated chains
The chains are rigid
The chains have bends (kinks) in
them (where the double bonds
occur). This means that they can’t
line up so closely next to each other
Structure of saturated chains
The chains are flexible
The chains are straight, so they can
line up closely next to each other
Unsaturated viscosity and density, mp/bp and state at room temp
Low
Less dense
Less IMF so low mp/bp
Liquid
