biological molecules - lipids and proteins

Question 1

what are the roles of lipids ?

Answer 1

• source of energy - when [o] they provide 2x the amount of energy of the same mass of carb
  -waterproofing - insoluble in water therefore makes it good for waterproofing
• insulation - fats -slow conductors therefore when stored - therefore helps retain body heat. Also act as electric insulators for myelin sheath around nerve cell.
  protection - fat usually stored around delicate organs e.g. kidneys.

Question 2

what is the bond between glycerol and fatty acid molecules called

Answer 2

ester bonds

Question 3

how does the structure of triglycerides relate to their properties

Answer 3

• have a high ratio of energy storing H-C bonds meaning they are an excellent source of energy.
• have a low mass to energy ratio meaning they can store a lot of energy in a small volume.
• non-polar meaning they are insoluble in water, water potential is not affected
• have a high ratio of H-O atoms , when oxidised they release water - good source of water.

Question 4

structure of phospholipids

Answer 4

• made of 2 fatty acid, 1 glycerol and one phospholipid
• hydrophilic heads
• hydrophobic tails
• is polar

Question 5

outline the emulsion test for lipids

Answer 5

• to 2cm3 of the sample that is being tested, add about 5cm3 of ethanol (because lipids are insoluble in h2o, they need to be dissolved in an organic solvent first.)
• shake thoroughly to make sure that they completely dissolve.
• add 5 cm3 of h2o to the sample and gently shake
• if lipid is present a cloudy white emulsion should form

Question 6

what is the name where many constituent amino acid monomers join together

Answer 6

this process is known as polymerisation . the resulting chain of many amino acids is known as a polypeptide.