lipids

Question 1

what is a triglyceride?

Answer 1

● a lipid

● one molecule of glycerol with 3 fatty acids attached to it

Question 2

why do fatty acid molecules have long tails made of hydrocarbons?

Answer 2

●tails are hydrophobic (repel water molecules)

●tails make lipids insoluble in water

●fatty acids have same base structure but hydrocarbon tail varies

Question 3

what reaction are triglycerides formed by?

Answer 3

● condensation reaction

● when ester bond formed between fatty acid and glycerol a molecule of water is released

Question 4

what are the 2 kinds of fatty acids?

Answer 4

saturated

● unsaturated

● difference is in their hydrocarbon tails (R group)

Question 5

saturated fatty acids don’t have any

Answer 5

double bonds between their carbon atoms
the fatty acid is saturated with hydrogen

Question 6

unsaturated fatty acids have at least

Answer 6

one double bond between carbon atoms, which causes the chain to kink

Question 7

what is a phospholipid?

Answer 7

● lipids found in cell membranes

● make up the bilayer of cell membranes

● similar to triglycerides except one of the fatty acid molecules is replaced by a phosphate group

● phosphate group is hydrophilic (attracts water)

● fatty acid tails are hydrophobic (repel water)

Question 8

how does the structure of triglycerides relate to their function?

Answer 8

● long hydrocarbon tails of fatty acids contain lots of chemical energy

● insoluble - doesn’t affect water potential of cell and cause water to enter cell by osmosis

● triglycerides clump together as insoluble droplets in cells as fatty acid tails are hydrophobic tails face inwards, shielding themselves from water with glycerol heads

Question 9

how does the structure of phospholipids relate to their function?

Answer 9

● heads are hydrophilic and tails are hydrophobic

● so they form double layer with heads facing out on each side

● centre of bilayer is hydrophobic so water soluble substances can’t easily pass through it

● membrane acts as barrier

Question 10

how do you test for lipids?

Answer 10

emulsion test

Question 11

what is the emulsion test?

Answer 11

● shake test substance with ethanol for a minute until it dissolves

● pour into water

● any lipid will show up as a milky emulsion

● more lipid there is the more noticeable milky colour will be