3.1.3 Lipids

Question 1

Solubility of lipids?

Answer 1

-insoluble in water
-soluble in organic solvents

Question 2

General structure of triglycerides

Answer 2

1 glycerol, 3 fatty acids

Question 3

Triglycerides have a low oxygen content meaning…

Answer 3

-high energy content due to lots of bonds to oxidise
-good respiratory substrate

Question 4

Triglycerides are hydrophobic because…

Answer 4

-fatty acids are non-polar
-useful for waterproofing

Question 5

Why are triglycerides good insulators?

Answer 5

-non-polar
-cannot become charged to lose electrons

Question 6

Triglycerides Structure: Why are they an excellent source of energy?

Answer 6

many C-H bonds, high ratio of energy

Question 7

Triglycerides Structure: Why can lots of energy be stored in a small volume?

Answer 7

low mass : energy ratio

Question 8

Triglycerides Structure: Why do they have no osmotic effect?

Answer 8

-insoluble in water
-as they are non-polar and large molecules

Question 9

Triglycerides Structure: Why are they a good source of water when oxidised?

Answer 9

high ratio of H:O atoms

Question 10

Phospholipids general structure

Answer 10

-phosphate group (hydrophilic head)
-2 fatty acids (hydrophobic)

Question 11

What does amphipathic mean?

Answer 11

containing both a hydrophilic and hydrophobic part (hydrophilic head and hydrophobic tail)

Question 12

Functions of phospholipids

Answer 12

-forms bilayer within cell (surface membranes)
-hydrophobic barrier

Question 13

5 main functions of lipids

Answer 13

1. flexibility of cell membranes
   2.energy source (when oxidised)
2. waterproofing (insoluble in water)
3. insulation
4. protection (e.g. kidney)

Question 14

Emulsion Test

Answer 14

-add ethanol to sample
-shake
-add water
-cloudy white emulsion = positive