lipids and fats

Question 1

lipids

Answer 1

• contains carbon, hydrogen and oxygen
• insoluble in water (hydrophobic property)
• soluble only in organic solvents (alcohol, propane etc.)
• in animals: animal fats (solid)
• in plants: plant oils (lipids)

Question 2

fats and oils

Answer 2

• formed by condensation reactions (removal of water) between fatty acids and glycerol
• 3 fatty acid molecules + 1 glycerol molecule –> triglyceride

Question 3

triglyceride

Answer 3

• hydrophobic properties make them clump together –> appears as a macromolecule
• saturated fatty acids: no double bonds
• unsaturated fatty acids: one or more double bonds present
• polyunsaturated: when several double bonds present

Question 4

role of fats and oils

Answer 4

• they release more than twice as much energy as carbohydrates –> forms a concentrated, insoluble energy source
• concentrated food reserves for long unfavourable seasons
• complete oxidation produces a large amount of metabolic water (helps animals to survive when there is little drinking water)
• buoyancy aid and heat insulation layer
• oils act as waterproofing for hair and feathers
• electrical insulation (around nerve cells)

Question 5

phospholipids

Answer 5

• similar to triglycerides except 1 of the fatty acids is replaced by phosphate group
• phosphate group is ionised and therefore hate-soluble (hydrophilic property)

Question 6

properties of water

Answer 6

• high specific heat capacity (allows for large/bulky organisms to have stable temperatures)
• high latent heat of vaporisation (allows for evaporation as a mechanism for cooling)
• water serves as the universal solvent in biological system
  (allows for chemical reactions to take place)
  (key component of tissues)
  (also helps transport dissolved substances)
• highly cohesive water molecules (allows water to be drawn up narrow columns such as xylem vessels)