3.1.3 Lipids Flashcards
(Lipids) What are lipids made from?
A variety of different components but they all contain hydrocarbons.
(Lipids) What do the components the lipid is made from relate to?
The lipid’s role.
(Lipids) Name two types of lipid.
Triglycerides and phospholipids
(Lipids) What do triglycerides consist of?
One molecule of glycerol with three fatty acids attached to it.
(Lipids) State a feature of fatty acid molecules?
Long ‘tails’ made of hydrocarbons which are hydrophobic
(Lipids) What does hydrophobic mean?
The substance repels water molecules.
(Lipids) What do the fatty acid molecule ‘tails’ make lipids?
Insoluble in water
(Lipids) Describe saturated fatty acids.
Don’t have any double bonds between their carbon atoms. ‘Saturated’ with hydrogen.
(Lipids) Describe unsaturated fatty acids.
Have double bonds between carbon atoms, which cause the chain to kink.
(Lipids) What are triglycerides formed by?
Condensation
(Lipids) During a condensation reaction, what bond forms between glycerol and a fatty acid?
Ester bond.
(Lipids) Describe fatty acids (4)
- Long chain carboxylic acids
- Typically 12-18 carbon atoms in a hydrocarbon chain
- Immiscible in water (won’t mix)
- Some contain carbon double bonds and other don’t
(Lipids) Properties of saturated fatty acids (5).
- Strong attraction between fatty acid chains
- High melting point
- Solid at room temperature
- Only have C-C so form linear hydrocarbon chains
- Fit closely in a regular pattern
(Lipids) Properties of unsaturated fatty acids (5).
- Fewer (so weaker) interactions between fatty acid chains
- Low melting points
- Liquid at room temperature
- 1+ C=C which causes hydrocarbon chain to bend
- Push each other apart forming irregular patterns
(Lipids) Describe condensation in lipids. (4)
- Produces a triglyceride
- Formed from a glycerol + 3 fatty acids
- 3 water molecules are released
- Formation of an ester bond
(Lipids) Describe the food/emulsion test for lipids. (4)
If the sample is solid then grind it.
Add 2cm3 of ethanol / alcohol and shake.
THEN add 2cm3 of water and shake.
Colour change from clear to white / milky emulsion.
(Lipids) What is a phospholipid made up of?
A glycerol molecule, 2 fatty acids and a phosphate group.
(Lipids) What are the two parts that a phospholipid is made up of?
- A hydrophilic head
- A hydrophobic tail
(Lipids) Describe the properties of a hydrophilic head.
Is attracted to water and faces “outwards”.
(Lipids) Describe the properties of a hydrophobic tail.
Repels water, tails turn “inward”.
(Lipids) What do phospholipids do in aqueous environments?
Form a bilayer due to their bipolar nature, e.g. in cell membranes, which produces a hydrophobic barrier between the inside and outside of cells.
(Lipids) What do hydrophilic head in phospholipids help?
To hold cell membranes together.
(Lipids) What can phospholipids form?
Glycolipids.
(Lipids) What are triglycerides mainly used as?
Energy storage molecules.
