lipids

Question 1

elemental composition

Answer 1

carbon, hydrogen, oxygen

Question 2

three classes of fatty acids

Answer 2

saturated, unsaturated and polyunsaturated

Question 3

essential fatty acid

Answer 3

cannot be made in the body therefore we must get them from food eg linoleic, linolenic, arachidonic fatty acids.

Question 4

functions of fatty acids

Answer 4

• formation of cell membranes for growth

- hardening effect of cholesterol thereby reduces the risk of coronary heart disease

Question 5

significance of trans fatty acids

Answer 5

• help reduce cholesterol
• oil changes the cis fatty acids to trans fatty acids due to high heat
• reduce high density of lipoproteins

Question 6

classification of lipids (animal)

Answer 6

• meat
• butter
• milk
• cheese

Question 7

classification of lipids (plant)

Answer 7

• nuts
• avocado
• vegetable oils
• margarine

Question 8

classification of lipids (marine)

Answer 8

• salmon
• mackerel
• tune
• cod liver oil

Question 9

properties of lipids

Answer 9

• solubility: insoluble in water but soluble in solvents eg petrol
  -heat: solid fata melt at 30-40 degrees
• plasticity: relates where a lipid is solid, liquid or spreadable. eg unsaturated fatty acids present the more solid eg margarine
• rancidity (oxidative) : results in unpleasant smell
  : aided by light
• rancidity (hydrolytic): when enzyme/bacteria hydrolise lipids changes to fatty acids and glycerol
  : can occur in freezer due to enzymes
  -hydrogenation: hydrogen (nickel catalyst) is added in unsaturated fatty acids converting oil into fats eg production of margarine
  -emulsification: when two liquids (water and oil) dont mix together

Question 10

effects of heat in lipids

Answer 10

• solid fat melts 30-40 degrees
• lipids boil at high temp 175-195 degrees
• smoke point: fats and oils start to decompose when heated. 200 degrees (fats) 250 degrees (oils)
• flash point: extreme overheating 310(fats) 325(oils)

Question 11

biological functions of lipids

Answer 11

• source of energy
• excess lipid is stored as adipose tissue
• protects the organs
• some unsaturated fats reduce cholesterol

Question 12

energe value

Answer 12

-9 kcal per gram

Question 13

digestion of lipids

Answer 13

• mouth: food is chewed
• stomach: fats melt
• small intestine: lipase from the pancreas digests lipids into fatty acids and glycerol
• bile: produced by the liver and secreted into the duodenum emulsifies lipids aiding their digestion

Question 14

absorption and utilisation of lipids

Answer 14

fatty and acids and glycerol are absorbed in the villi of the small intestine. the lymph system then carries the digested lipids and deposits into the blood stream at the subclavian vein.