1.3 - Lipids Flashcards
1) Describe the structure of a triglyceride
One molecule of glycerol and three molecules of fatty acid
1) 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.
1) Draw a triglyceride – circle the ester bond
Check notes
1) 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
1) Describe the structure of a phospholipid
It is made of 1 glycerol molecule, 1 phosphate group and 2 fatty acid chains
1) 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.
1) 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.
1) Draw a phospholipid and label the hydrophilic and hydrophobic parts
Check notes
1) Describe how Phospholipids can arrange themselves to form a cell membrane. Draw and label a diagram to show this.
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.
Properties and characteristics of unsaturated fatty acids
At least one double bond between carbon atoms in the fatty acid chain
Not saturated with hydrogen atoms
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
Low viscosity
Less dense
Low melting point and boiling point
Less intermolecular forces – so less energy required to overcome them
Usually liquid @ room temp
Properties and characteristics of saturated fatty acid chains
ONLY single bonds between carbon atoms in the fatty acid chain (no C=C bonds)
Yes saturated with hydrogen atoms
The chains are flexible
The chains are straight, so they can line
up closely next to each other
High viscosity
More dense
High melting point and boiling point
More of intermolecular forces – lots of energy needed to overcome them
Usually solid
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
