lipids

Question 1

Describe the test for lipids

Answer 1

1) dissolve solid samples in ethanol
2) add equal volume of distilled water and shake
3) positive result= milky white emulsion

Question 2

how do triglycerides form?

Answer 2

• condensation reaction
• between 1 glycerol and 3 fatty acids
• forms ester bonds
• one water molecule released per ester bond

Question 3

what can the fatty acid chains on triglycerides also be known as

Answer 3

r group
- because number of carbon and hydrogens can vary

Question 4

what is the difference between saturated and UNsaturated

Answer 4

saturated= the hydrocarbon chain only has SINGLE bonds between carbons
unsaturated= hydrocarbon cahin consists of at least one double bond between carbons

MUST PUT ‘BETWEEN CARBONS’ TO GET MARK!!!

Question 5

list 4 ways in which triglyceride structure results in its properties

Answer 5

1) long hydrocarbon chains so a lot of energy is stored in molecule
2) high ratio of hydrogen to oxygen atoms, so triglcerides act as metabolic water source (can release water if oxidised) good for animals in deserts e.g. camels
3) fatty acid tails are hydrophobic, so triglycerides ae insoluable in water, so triglycerides do not affect water potential and osmosis
4) relativly low mass, so alot can be stored without increasing mass + preventing movement

Question 6

how do phospholipids form?

Answer 6

• glycerol molecule, 2 fatty acid chains, phosphate group (attatched to glycerol)
• condensation reaction bonds fatty acids and glycerol
• forms ester bonds

Question 7

list the properties of phospholipids

Answer 7

• hydrophillic head can attract water (because it is charged)
• hydrophobic tail repels water (because it is uncharged)
• forms phospholipid bilayer membrane structure (akes up plasma membrane around cells)

Question 8

do hydrophillic heads point out or in

Answer 8

• outwards
• can interact with water

Question 9

do hydrophobic tails point out or in

Answer 9

• inwards
• so water soluable substances cannot easily pass through membrane

Question 10

what would happen if triglycerides didnt repel water?

Answer 10

• water would enter cell through osmosis
• cells would swell up + possibly burst

Question 11

why are unsaturated fatty acids liquid at room temperature?

Answer 11

• double bonds ‘kink’ the carbon chain
• so unsaturated fats cannot pack together tightly