lipids

what are triglycerides and phospholipids examples of?

groups of lipid

how are triglycerides formed?

• by the condensation of 1 molecule of glycerol and 3 molecules of fatty acid

• joined by 3 ester bonds

• 3 water molecules produced

how is an ester bond formed?

by a condensation reaction between glycerol and a fatty acid (RCOOH)

glycerol

structure of phospholipids

1 glycerol, 2 fatty acids, 1 phosphate group

how the structure of triglycerides results in its properties

1. energy storage: due to the large ratio of energy-storing carbon-hydrogen bonds compared to the number of carbon atoms, a lot of energy is stored in the molecule.

2. metabolic water source: due to the high ratio of hydrogen to oxygen atoms. triglycerides can release water if they are oxidised. this is essential for animals in desserts, such as camels.

3. do not affect water potential and osmosis: because they are large and hydrophobic, making them insoluble in water.

4. lipids have a relatively low mass: therefore a lot can be stored without increasing the mass and preventing movement.

saturated fatty acids

the hydrocarbon chain has only single bonds between carbons

unsaturated fatty acids

the hydrocarbon chain consists of at least one double bond between carbons

how the structure of phospholipids results in its properties

• the hydrophilic head can attract water as it is charged

• the hydrophilic head is soluble but the hydrophobic tail is insoluble

• repels other fats because the phosphate is charged

• the fatty acid chain (hydrophobic tail) is not charged and it repels water, but will mix with fats

• phospholipids have two charged regions, so they are polar

• in water, they are position so that the heads are exposed to water and the tails are not

• this forms a phospholipid bilayer membrane structure which makes up the plasma membrane around cells

what is the outside layer of phospholipids in a phospholipid bilayer called?

extracellular

what is the inside layer of phospholipids in a phospholipid bilayer called?

intracellular

in phospholipids, what is one of the fatty acids of a triglyceride substituted by?

a phosphate-containing group

emulsion test for lipids

1. dissolve sample in ethanol

2. add oil then add ethanol and mix

3. then add distilled water and mix again

4. if a white emulsion appears a lipid is present