Lipids Flashcards
1
Q
What are the properties of lipids?
A
- contain carbon, hydrogen and oxygen
- not polymers
- insoluble in water
- soluble in organic solvents
2
Q
What are the two types of lipids?
A
triglycerides and phospholipids
3
Q
What are the roles of lipids?
A
- are in the cell membrane of organisms
- a source of energy
- waterproofing
- insulation
- protection
4
Q
What is the structure of a triglyceride?
A
- the fatty acids combined with a glycerol backbone
- each fatty acid is joined by an ester bond with the glycerol molecule through a condensation reaction
5
Q
What causes the difference in triglycerides?
A
- the glycerol molecules are the same so differences are caused by the r groups of fatty acids
- r groups can be saturated or unsaturated
6
Q
What is unsaturated?
A
the r group of a fatty acid contains a double carbon-to-carbon bond
7
Q
What is the structure of triglycerides related to their properties?
A
- high ratio of carbon to hydrogen bonds to carbon atoms, good stores of energy
- low mass so they are good energy stores
- large, non-polar and insoluble so they don’t affect the osmotic potential of cells
- high ratio of hydrogen to oxygen atoms so they release water when oxidised and are a source for desert animals
8
Q
What is the structure of phospholipids?
A
- two fatty acids and a phosphate molecule joined by ester bonds to a glycerol molecule
- hydrophilic head and a hydrophobic tail making phospholipids polar
9
Q
What is the structure of phospholipids related to their properties?
A
- due to the hydrophilic head and hydrophobic tail allowing phospholipids to form a bilayer within cell membranes
- the hydrophilic head helps hold at the surface of the cell membrane
- the phospholipid structure allows them to form glycolipids by combining with carbohydrates. These glycolipids are important for cell recognition
10
Q
What is the test for lipids?
A
- add your sample and ethanol and mix
- add an equal volume of water as ethanol and mix
- a positive test is a milky white emulsion
