3.1.3 Lipids

Question 1

What are lipids ?

Answer 1

Lipids are a mixed group of hydrophobic compounds composed of the elements carbon,
hydrogen and oxygen.

Question 2

Define hydrophobic

Answer 2

water fearing, non-polar molecules, lipid soluble

Question 3

Define hydrophillic

Answer 3

water loving, polar molecules, water soluble (not soluble in lipids)

Question 4

What are examples of complex lipids ?

Answer 4

Triglycerides , Phospholipids and waxes

Question 5

What are examples of simple lipids ?

Answer 5

Steroids and terpenes

Question 6

Describe the emulsion test for lipids and how it could be improved ?

Answer 6

1. Add ethanol to the test substance and shake thoroughly for about a minute so
   that it dissolves
2. Add water to the solution
3. Any lipid will show as a milky emulsion and the more lipid there is, the more
   noticeable the milky colour will be
4. The test can be improved further by adding the dye Sudan III, which will stain the
   lipids red

Question 7

What are triglycerides made of ?

Answer 7

One molecule glycerol and three fatty acids

Question 8

What are properties of triglycerides ?

Answer 8

‒ Triglycerides are insoluble in water.
‒ They are used for storage, insulation and protection in fatty tissue (or adipose
tissue) found under the skin (subcutaneous) or surrounding organs.
‒ They yield more energy per unit mass than other compounds so are good for
energy storage.

Question 9

What makes fatty acids saturated ?

Answer 9

May have no C=C (double) bonds in the chain, making them saturated and straight
chains

Question 10

What makes fatty acids unsaturated ?

Answer 10

May have one (mono) or several (poly) C=C bonds, making them unsaturated. This
causes kinks, bends in the chains. This lowers the melting point

Question 11

What type of fats are solid at room temperature and what type of fats are liquids at room temperature ?

Answer 11

‒ Plant and fish fats are liquids at room temperature (oils) as they have a high
degree of unsaturation.
‒ Animal fats are solids at room temperature as they are saturated fats.

Question 12

What property does the fatty acids have that repel water ?

Answer 12

hydrophobic-makes lipid insoluble

Question 13

What is the structure of phospholipids ?

Answer 13

‒ Similar to triglycerides, but a phosphate group in place of one fatty acid chain.
‒ The phosphate head is hydrophilic and polar (water soluble)
‒ Two non-polar hydrophobic “tails” (the fatty acid chains).

Question 14

What are the main components of cell/plasma membranes ?

Answer 14

Phospholipids

Question 15

What happens when phospholipids are mixed with water ?

Answer 15

Phospholipids form droplet spheres with the hydrophilic
heads facing the water and the hydrophobic tails facing each other. This is called
a micelle.