2 - ICH - Lipids

Question 1

Define a lipid

Answer 1

Organic compounds that are insoluble in water

Question 2

Elements that make up a lipid?

Answer 2

Carbon, hydrogen, oxygen (same as carbohydrate)

Much less oxygen present than in carbohydrates

Question 3

Formula for glycerol

Answer 3

C₃H₈O₃

Question 4

General formula for fatty acid

Answer 4

CH₃(CH₂)_nCOOH

Question 5

Examples of:

Saturated lipid (2)

Unsaturated lipid (1)

Answer 5

Saturated: stearic acid and palmitic acid

Unsaturated: oleic acid

Question 6

Difference between Fats and Oils?

Answer 6

Fats = Solid at RTP

Oils = Liquid at RTP

Question 7

What is a triglyceride made of?

Answer 7

Glycerol + (3x)Fatty acid → Triglyceride

Question 8

Name 2 types of essential fatty acids

Answer 8

Omega - 3 fatty acid

Omega - 6 fatty acid

Question 9

Oils/fats which are unsaturated/saturated?

Answer 9

Oils = Unsaturated lipids

Fats = Saturated lipids

Question 10

Which type of lipid have kinks? Benefit?

Answer 10

Kink = in unsaturated lipids i.e. oils

Having kinks in the hydrocarbon chain means that they are loosely packed together, hence oils are liquid at RPT

Question 11

Why are:

Oils liquid at RPT and fats are solid at RPT?

Answer 11

Oils = Have “kinks” which means that the molecules are loosely packed together

Fats = Don’t have kinks, are tightly packed together

Question 12

Describe the structure of a phospholipid

Answer 12

Question 13

Why are phospholipids amphipathic

Answer 13

Amphipathic = when a part of a molecule will dissolve and another part won’t

It’s a polar molecule.

The hydrophilic head will dissolve and the hydrophobic tail won’t

Question 14

What are phospholipids made of?

Use?

Answer 14

Similar to triglycerides but one of the fatty acids are replaced by a phosphate group.

Major component of cell membranes.

(Arranged in a bilayer with proteins)

Question 15

What is a glycolipid?

Uses?

Answer 15

Lipid + Carbohydrate → Glycolipid

Cell membranes

Question 16

Uses of wax?

Answer 16

Wax is another type of lipid.

Needed on the leaves of plants. Waterproofing.

Question 17

What is special about Steroids and terpenes?

Answer 17

They’re classed as lipids but don’t contain any fatty acids

Question 18

Structure of steroids?

Answer 18

Each steroid differs from the side group that’s attached to the nucleus.

Question 19

Examples of steroids? (5)

Answer 19

Important in animals:

-Cholesterol

Some hormones are steroids e.g:

• Testosterone
• Progesterone
• Oestrogen
• Cortisone

Question 20

Example of terpenes?

Answer 20

Important to plants.

• Gibberellins (plant hormones)
• Carotenoids (pigments used in photosynthesis)

Question 21

What does the Emulsion test do?

Answer 21

Test for lipids based on the fact that lipids are soluble in organic solvents

Question 22

Describe the Emulsion Test

Answer 22

1 - Place small amount of the sample into a test tube. If it’s solid e.g. peanut, cheese… grind it up to increase surface area.

2 - Add 2cm³ of an organic solvent e.g. alcohol or propanone and shake. Any lipid present will dissolve into the solvent.

3 - Add an excess of water.

4 - Lipid will come out of solution produce a cloudy emulsion (tiny lipid droplets suspended in the water).

Cloudy emulsion = Lipid present

Question 23

How to make the emulsion test:

1 - Semi quantitative

2 - Fully quantitative

Answer 23

1 - Use a comparisson chart

2 - Use a colourimeter.