Lipids (3.1.3)

Question 1

Lipids are not formed from monomers, but are made from a variety of components including hydrocarbons. What are the 2 main types of lipids?

Answer 1

1) Triglycerides
2) Phospholipids

Question 2

Describe the structure of a triglyceride.

Answer 2

-Formed by the condensation of 1 glycerol molecule and 3 fatty acids, creating ester bonds between the molecules
-Fatty acid tails are hydrophobic and made of hydrocarbons

Question 3

There are 2 kinds of fatty acids, what are they and what varies between their structure?

Answer 3

Saturated fatty acids: Don’t have any carbon to carbon double bonds (saturated with hydrogen) in their variable ‘R’ group
Unsaturated fatty acids: Do have carbon to carbon double bonds in their variable ‘R’ group

Question 4

Describe the structure of a phospholipid.

Answer 4

-Formed by the condensation of 1 glycerol molecule, 2 fatty acids and a phosphate group, creating ester bonds between the molecules
-Phosphate group and glycerol is hydrophilic and fatty acid tails are hydrophobic

Question 5

What are the properties of a triglyceride?

Answer 5

-Used as energy storage molecules as their fatty acid tails contain lots of chemical energy, so lots of that energy is released when it’s hydrolysed
-Insoluble in water so doesn’t affect water potential of the cell, causing water to move in via osmosis
-In cells, the tails face inwards shielding themselves from water with their glycerol heads

Question 6

What are the properties of a phospholipid?

Answer 6

-They make up the bilayer of cell membranes (which control what enters/leaves the cell)
-Form a double layer with hydrophilic heads facing towards the water and as the centre of the bilayer is hydrophobic, soluble substances cannot easily pass through - membrane acts as a barrier

Question 7

Explain the emulsion test for lipids

Answer 7

1) Shake sample with ethanol (alcohol) for 1 minute
2) Add solution to some water
3) If solution forms a white, milky emulsion = lipids are present