Lipids

Question 1

Describe the test for lipids

Answer 1

The Emulsion Test:
1. Take 2cm3 of the test sample and add 5cm3 of ethanol.
2. Shake the test tube thoroughly to dissolve any liquid in the sample
3. Add 5 cm3 of water and shake gently
If present, a milky white emulsion will form as lipid droplets spread throughout the water (from the carbohydrates.)

Question 2

Define Emulsion

Answer 2

A fine dispersion of minute droplets of one liquid in another, in which it is not soluble or miscible

Question 3

Information on Lipids 5

Answer 3

-insoluble in water but soluble and can be dissolved using organic substances e.g., alcohols and acetones
- Good source of energy: provide x2 more the same mass as Carbohydrates as contains lots of carbon and hydrogen bonds.
- Waterproofing in plants and animals: waxy cuticle on leaves and sebaceous fluid on skin
-Good insulating material as poor conductor of heat
-protect soft organs

Question 4

How do triglycerides form?

Answer 4

Condensation reaction between 3 fatty acids and 1 glycerol molecule forming ester bonds, and releasing 3 water molecules.

Question 5

Properties of fatty acids

Answer 5

• glycerol same but different fatty acids in lipids: different properties from composition of fatty acids tail
• tails are hydrophobic, making them insoluble
• carbon atom links fatty acid to glycerol
• RCOOHH

Question 6

Saturates fatty acid chains:

Answer 6

• every Carbon atom is indeed to as many hydrogen atoms. No more can be added
  -found in animal fats
  -straight carbon chains
• pack together to form solids at room temperature

Question 7

Unsaturated fatty acid chains

Answer 7

• double bonds: kinks in carbon chain
• found in vegetable oils, nuts and fish
• don’t pack together easily so liquids at room temperature
• more double bonds = more kinks

Question 8

Saturated fats definition

Answer 8

Fats containing high proportion of fatty acid molecules without double bonds.

Question 9

Unsaturated fats definition:

Answer 9

High proportion of fatty acids with at least one double bond.

Question 10

Structure and function of triglycerides: 5

Answer 10

• high ratio of energy storing carbon hydrogen bonds (excellent energy source.)
• low mass to energy ratio: lots of energy stored in small mass. Beneficial to animals who need energy store without carrying extra weight.
• insoluble - don’t effect osmosis in cells.
• when oxidised, release water
  -thermal insulation

Question 11

Formation of phospholipids

Answer 11

• a glycerol backbone, a polar hydrophilic phosphate group and hydrophobic fatty acid chains (2)
• condensation reaction between them and forming ester bonds between glycerol and fatty acids
  -tails splay outwards: waterproofing and inwards = phospholipid bilayer in membrane.

Question 12

Similarities of phospholipids and triglycerides: 3

Answer 12

• both formed by condensation reaction with ester bonds.
• glycerol and fatty acid, C and H and O
• Possess hydrophobic properties
  -may be attached to unsaturated or saturated fatty acid.

Question 13

Differences between phospholipids and triglycerides: 4

Answer 13

• T = energy storage when oxidised P = membrane formation
• P = can form bilayer
• T= entirely hydrophobic P = part is hydrophobic and hydrophilic
• T = glycerol and 3 fatty acids. P = glycerol, phosphate group and 2 fatty acids

Question 14

Are triglycerides and phospholipids polymers?

Answer 14

Macromolecules.
They are not made by a small repeating unit.