lipids

Question 1

what 3 characteristics do lipids share?

Answer 1

• all contain the elements carbon, Hydrogen, Oxygen
• they are non-polar molecules do to large number of carbons and hydrogens
• so are insoluble of water
• soluble in other organic solvents e.g. alchohol

Question 2

what are the 2 main groups of lipids

Answer 2

• triglycerides
• phospholipids

Question 3

Triglyceride

Answer 3

(fats & oils)
* a component of our diet
* made of glycerol and 3 hydrocarbon chains (fatty acids)

Question 4

Phospholipids

Answer 4

a component of cell membranes

Question 5

what is a fatty acid

Answer 5

• a long hydrocarbon chain with a carboxylic acid group at one end
• some fatty acids contain carbon double bonds and some dont

Question 6

what is a saturated fatty acid

Answer 6

only have a C-C so form linear hydrocarbons chains
- fatty acids saturated fit closely together in a regular pattern

Question 7

unsaturated fatty acid

Answer 7

have 1 or more c=c bond which causes the hydrocarbon chain to bend.
* therefore unsaturated fatty acids push eachother apart forming irregular patterns

Question 8

properties of saturated fatty acids

Answer 8

• fatty acids are closed can pack closely together
• high melting point
• solids at room temp
• strong attractions (intermolecular bonds) between fatty acid chains

Question 9

properties of unsaturated fatty acids

Answer 9

• weaker attractions (intermollecular bonds) between fatty acid chains
• lower melting point
• non-linear chains dont allow molecules to be tightly packed together.

Question 10

what are features of a triglyceride

Answer 10

• 3 fatty acids combined with a glycerol
• large insoluble molecules (hydrophobic)
• they form an ester bond = condensation reaction between glycerol & fatty acids

Question 11

condensation reaction

Answer 11

• produces a triglyceride
• formed from a glycerol and 3 fatty acids
• 3 ester bonds are formed

Question 12

hydrolisis reaction

Answer 12

• trigliceride is split by the addition of 3 water molecules
• 3 ester bonds broken
• glycerol and fatty acids formed

Question 13

describe the food test: emulsion test

Answer 13

1. mix sample being tested withe alchohol (e.g. ethanol) in a test tube
2. shake the tube thoroughly
3. add cold water and shake gently
4. if a milky, white emulsion is formed then it indicates the presence of a LIPID