1.5 Lipids

Question 1

What are characteristics of lipids?

Answer 1

Contain:
-carbon, hydrogen and oxygen
- proportion of oxygen to carbon and hydrogen is smaller in carbs.
- insoluble in water
- soluble in organic solvents such as alcohol

Question 2

What are the 2 main groups for lipids?

Answer 2

Triglycerides (fats and oils)
Phospolipids

Question 3

What is the role of lipids in the cell membrane?

Answer 3

they contribute to flexibility of membranes and the transfer of lipid-soluble substances across them

Question 4

What are the roles of lipids?

Answer 4

• source of energy
• waterproofing (insoluble in water)
• insulation
• protection

Question 5

What are Triglycerides made up of? What bond is formed between them?

Answer 5

3 fatty acids and glycerol
An ESTER bond is formed

Question 6

What is the difference between saturated, mono-unsaturated and polysaturated lipids?

Answer 6

Saturated - no double bonds between carbon atoms
Mono-unsaturated - one double bond between the carbon atoms
Polysaturated - more than one double bond between carbon atoms

Question 7

How does the structure of Triglycerides relate to its properties?

Answer 7

• High ratio of energy-storing carbon-hydrogen bonds to carbon atoms
• Low mass to energy ratio, good storage molecules as lots of energy can be stored in small volumes
• Large and non-polar, insoluble in water so doesn’t affect osmosis of water in cell

Question 8

How is a phospholipid formed?

Answer 8

The fatty acid tails are replaced with phosphate molecules

Question 9

Which part of the phospholipid is hydrophobic and which is hydrophillic?

Answer 9

Hydrophobic ‘tail’, repels water
Hydrophilic head’’, attracts water

Question 10

What is the test for lipids?

Answer 10

1) Add 2cm^3 of sample being tested and then add 5cm^3 of ethanol
2) Shake tube thoroughly to dissolve any lipid in the sample
3) Add 5cm^3 of water and shake gently
4) A milky-white emulsion indicates the presence of a lipid