Lipids Flashcards
What are some characteristics of lipids?
- They all contain carbon, hydrogen and a small amount of oxygen.
- They are non-polar (due to the large percentage of carbons and hydrogens) and so are insoluble in water (they are hydrophobic).
- They are soluble in organic solvents e.g. acetone, alcohols…
What are the two main groups of lipids?
Triglycerides and phospholipids
What is the function of triglycerides?
Energy storage in fat (adipose) cells.
What is the function of phospholipids?
Main component of cell membranes.
What is the difference between saturated fatty acids and unsaturated fatty acids?
- Saturated fatty acids have only C-C bonds so form linear chains.
- Unsaturated fatty acids have one or more C=C bonds which causes the hydrocarbon to bend.
How are triglycerides formed?
They are formed by the condensation of one molecule of glycerol and three molecules of fatty acid (3 water molecules are released).
How does an ester bond form?
A condensation reaction between glycerol and a fatty acid (RCOOH) forms an ester bond.
How are phospholipids formed?
They are formed by the condensation of one molecule of glycerol to two fatty acids and one phosphate group.
How is the phospholipid bilayer created?
- The phosphate and glycerol form a hydrophilic head and the fatty acids form hydrophobic tails. -
- When the phospholipids are placed in water, they position themselves so that the hydrophilic heads are close to the water and the hydrophobic tails are as far away from the water as possible.
What is the name of the biochemical test for lipids?
The emulsion test
Describe the biochemical test for lipids.
- Mix the sample being tested with 5cm^3 of alcohol in a test tube.
- Shake the tube thoroughly.
- Add 5cm^3 of cold water and shake gently.
- If a milky white colour is formed then this indicates the presence of a lipid.
- As a control, repeat the procedure with just water, the solution should remain clear.
What is the structure of triglycerides?
- They are formed from one glycerol molecule attached to three fatty acids by ester bonds.
- They contain the elements carbon, hydrogen and oxygen.
- They have ester bonds.
- They can contain both saturated and unsaturated fatty acids.
What are the properties of triglycerides?
- They are hydrophobic.
- They are insoluble in water.
What is the structure of phospholipids?
- They are formed from one glycerol molecule attached to two fatty acids and one phosphate group.
- They contain the elements carbon, hydrogen, oxygen and phosphorous.
- They contain a phosphate group.
- They have ester bonds.
- They can contain both saturated and unsaturated fatty acids.
What are the properties of phospholipids?
- They are both hydrophobic and hydrophilic.
- They form bilayers in water.
