lipids

Question 1

what 4 main characteristics do lipids share?

Answer 1

• they all contain carbon, oxygen and hydrogen
  *the proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
  *they are insoluble in water
  *they are soluble in organic solvents such as alcohols and acetone

Question 2

what is the role of phospholipids in the cell membrane?

Answer 2

they form a bilayer that contributes to flexibility and protects the cell.

Question 3

what are 4 other roles of lipids?

Answer 3

1. source of energy
2. waterproofing (insoluble in water)
3. insulation (fats are slow conductors of heat)
4. protection (fat is often stored around delicate organs)

Question 4

what type of bond forms between each fatty acid and glycerol in a condensation reaction?

Answer 4

ester bond

Question 5

if the hydrocarbon chain has no carbon-carbon double bonds is it saturated or unsaturated?

Answer 5

saturated

Question 6

what is it called if there is one single double carbon bond in the hydrocarbon chain?

Answer 6

mono-unsaturated

Question 7

do unsaturated fatty acids have a higher or lower melting point?

Answer 7

lower melting point (liquid at room temp.

Question 8

how does the structure of triglycerides relate to their functions?

Answer 8

1. high ratio of carbon-hydrogen bonds that are good for energy storing
2. low mass to energy ratio so they are good for storage as energy is stored in small volumes
3. large, non-polar so they are insoluble in water (don’t affect water potential)
4. high ration of hydrogen to oxygen atoms, so they become a good water source

Question 9

how does the structure of phospholipids differ to that of triglycerides?

Answer 9

one of the fatty acid molecules is replaced by a phosphate

Question 10

what two parts make up a phospholipid?

Answer 10

1. hydrophilic head
2. hydrophobic tail

Question 11

how does the structure of phospholipids relate to their functions?

Answer 11

1. polar – form a phospholipid bilayer in aqueous environments (hydrophobic barrier is formed between the inside and outside of the cell)
2. can form glycolipids by combining with carbohydrates in the cell surface membrane

Question 12

what is the test for lipids?

Answer 12

emulsion test

Question 13

describe the emulsion test for lipids

Answer 13

1. dissolve solid samples in ethanol
2. shake to dissolve any lipid
3. add water and gently shake
4. positive result shows a milky white emulsion

Question 14

how does the main function of phospholipids and triglycerides differ?

Answer 14

phospholipids are mainly used in membrane formation where as triglycerides primary use is as a storage molecule