lipids

Question 1

lipids - functions

Answer 1

forms bilayer in plasma membranes; some are hormones; respiratory substrate

Question 2

two groups of lipids

Answer 2

triglycerides and phospholipids

Question 3

how are triglycerides formed?

Answer 3

formed by the condensation of one molecule of glycerol and three fatty acids

Question 4

what forms an ester bond?

Answer 4

a condensation reaction between glycerol and a fatty acid forms an ester bond

Question 5

triglycerides - properties

Answer 5

insoluble in water as they are non-polar

Question 6

triglycerides - properties related to structure

Answer 6

• energy storage molecules
• insoluble in water (no effect on water potential of cell_
• high ratio of C-H bonds to C atoms in hydrocarbon tail so release more energy
• insulation + protection

Question 7

phospholipids

Answer 7

in phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group

Question 8

phospholipids - properties

Answer 8

have a hydrophilic head and hydrophobic tails and form plasma membrane

Question 9

phospholipids - properties related to structure

Answer 9

• form bilayer in cell membrane, allowing diffusion of non-polar small molecules
• phosphate heads are polar/hydrophilic so are attracted to water to orient to aqueous environment
• fatty acid tails are non-polar/hydrophobic so are repelled by water -> orient to interior of membrane -> repels polar/ changed molecules

Question 10

saturated fatty acids

Answer 10

no C=C (double) in hydrocarbon chains; all carbons fully saturated with hydrogen

Question 11

unsaturated fatty acids

Answer 11

one or more C=C double bonds in hydrocarbon chain

Question 12

what is the biochemical test for lipids?

Answer 12

emulsion test

Question 13

emulsion test for lipids

Answer 13

1. add ethanol and shake (dissolves lipids)
2. then add water
3. positive: milky/ cloudy white emulsion