1.3 Lipids

Question 1

How are triglycerides formed?

Answer 1

By the condensation of 1 molecule of glycerol and 3 fatty acids

Question 2

What does a condensation reaction between glycerol and fatty acid forms?

Answer 2

Ester bond

Question 3

Properties related to triglycerides structure:

Answer 3

Energy storage molecule
- High ratio of C-H bonds to C atoms in hydrocarbon tail so release more energy than the same mass of carbohydrates
- Insoluble in water so no effect on water potential of cell

Question 4

What is the fatty acid in a phospholipid replaced with?

Answer 4

Phosphate-containing group

Question 5

Properties related to a phospholipid’s structure:

Answer 5

Form bilayer in cell membrane, allowing diffusion of non-polar/small molecules
- Phosphate heads are polar/hydrophillic so are attracted to water -> orient to aqueous environment either side of membrane
- Fatty acids tails are non-polar/hydrophobic so are repelled by water -> orient to interior of membrane -> repels polar charged molecules

Question 6

What are saturated fatty acids?

Answer 6

No C=C double bonds in hydrocarbon chain; all carbons fully saturated with hydrocarbon

Question 7

What are unsaturated fatty acids?

Answer 7

One or more C=C double bonds

Question 8

What is the emulsion test for lipids?

Answer 8

1. Add ethanol and shake
2. Then add water
3. POSITIVE: milky/cloudy emulsion