LIPIDS

Question 1

Lipid examples

Answer 1

triglycerides
phospholipids
glycolipids
cholestrol

Question 2

what are molecular proportions in lipids

Answer 2

lots of carbons and hydrogen atoms
little oxygen atoms

Question 3

macromolecules

Answer 3

a very large organic molecule

Question 4

triglyceride structure

Answer 4

one glycerol molecule C3H5(OH)3
three fatty acid chains

Question 5

glycerol

Answer 5

has 3 -C
has 3 -OH
has 5 -H
they are alcohols

Question 6

fatty acids

Answer 6

have carboxyl group (-COOH)
acidic as carboxyl ionises to form H+

Question 7

saturated

Answer 7

only carbon-carbon single bonds present
exist as solid as high bp

Question 8

what bonds form between glycerol and fatty acid in triglycerides

Answer 8

ester bonds (-cooc)

Question 8

unsaturated

Answer 8

c–c double bond present
so lower boiling point as double bond causes bend/kink in structure so weaker intermolecular forces between fatty acid chains
exist as liquid (e.g oil)

Question 9

fuctions of triglycerides

Answer 9

• energy source as it can be broken down in resp to release enery and generate ATP
  (produces more energy than sugar/carbs)
• energy store as it is insoluble in water it can be stored in adipose cells under skin
• insulation as adipose tissue under skin trap heat in
• insulation of nerves as forms myelin sheath for faster electrical impulse transmittion
• bouyancy as lipids are less dense than water (oil floats on water)
• protects plants (waxy cover of plants)

Question 10

phospholipids structure

Answer 10

1 glycerol
2 fatty acids
1 phosphate group

Question 11

phospholipids in water

Answer 11

phosphate group has a negative charge so phospholipids are polar (attracted to water)
but the fatty acid tails are non polar (water repelant)
so phospholipids have a hydrophillic head but hydrophobic tail (amphipathic)

Question 12

micelles

Answer 12

tiny balls with hydrophillic head outwards and hydrophobic tails inwards

Question 13

why are phospholipids good membranes

Answer 13

phospholipids may be free to move around in their layer but they wont ever expose their tails to water so they have stability
selectively permeable so only small, non-polar substances can pass through

Question 14

cholestrol structure

Answer 14

sterol (steroid alcohol)

Question 15

where is cholestrol made

Answer 15

liver in animal

Question 16

stigmasterol

Answer 16

cholesterol derivative in plants

Question 17

steroid hormones (made from cholesterol)

Answer 17

• vit D
• oestrogen
• testosterone
  are all hydrophobic and small so can pass through phospholipid bilayers

Question 18

test for presence of lipids

Answer 18

mix sample and ethanol in one test tube
pour another test tube w only water
pour solution into test tube w water
cloudy white emulsion forms (+ result)
stays colourless (- result)