1.3 Lipids

Question 1

What are lipids used for?

Answer 1

Insulation
Energy store
Protection of organs
Make up cell membranes 
Waxy cuticle layer (waterproofing)

Question 2

What is a common lipid called?

Answer 2

Triglyceride

Question 3

Is a triglyceride a polymer? Why?

Answer 3

No

I has no repeated sub-units

Question 4

What elements is a triglyceride made from?

Answer 4

Carbon
Hydrogen
Oxygen

Far more carbon and hydrogen than oxygen

Question 5

How is a triglyceride built?

Answer 5

4 molecules

1 glycerol molecule
3 fatty acid chains attached

Question 6

What is the main property of triglycerides?

Answer 6

It is insoluble in water as no OH groups

Therefore hydrophobic

(The glycerol and fatty acid chains are separately soluble)

Question 7

What are lipids soluble in?

Answer 7

Organic solvents

Alcohols and acetone

Question 8

What is the general formula of a fatty acid?

Answer 8

RCOOH

O
|| R-C-O-H

Question 9

What are the two types of fatty acids?

Answer 9

Saturated

Unsaturated

Question 10

What are the properties of saturated fatty acids?

Answer 10

All single carbon carbon bonds
Straight chains
Denser
Solid at room temperature - eg animal fat

Question 11

What are the properties of unsaturated fatty acids?

Answer 11

One or more carbon carbon double bonds
Bent chains
Less dense
Liquids at room temperature - eg plant oils

Question 12

What are the different names for unsaturated chains?

Answer 12

Monosaturated (1 c=c)

Polyunsaturated (+1 c=c)

Question 13

What is the structure of glycerol?

Answer 13

H   H   H
      |     |     | 
H- C - C - C - H
      |     |     |
    OH  OH  OH

Question 14

What reaction forms a triglyceride?

Answer 14

Condensation reaction

Question 15

What bond is formed in condensation of glycerol and fatty acid chains? How many?

Answer 15

Ester bond

3 bonds

Question 16

What are the products are formed in a condensation reaction?

Answer 16

1 triglyceride molecule

3 waters

Question 17

What are the uses of triglycerides?

Answer 17

Energy rich - high ratio of C-H bonds

Good storage - large non-polar molecules, don’t affect osmosis and low mass to energy ratio

Source of water - release water when oxidised as high ratio of H-O (good for camels)

Question 18

What is the test for lipids?

Answer 18

Add 5cm3 of alcohol(ethanol) to 2cm3 of the sample
Crush up first if solid sample (seeds)
Possible filtration if solid present
Shake the solution to dissolve the lipid
Add 5cm3 of water and shake
A cloudy white emulsion indicates presence of a lipid
Repeat with water as the sample to compare as a control group

Question 19

Why is a cloudy white emulsion formed in the lipids test?

Answer 19

You are putting two immiscible liquids together forming an emulsion

Question 20

What is another type of lipid?

Answer 20

Phospholipid

Question 21

How is the structure of a phospholipids different?

Answer 21

It has only 2 fatty acid chains attached to the glycerol and 1 phosphate group attached instead

Question 22

What are the properties of the glycerol/phosphate group head?

Answer 22

Hydrophilic

As the phosphate is charged so can be dissolved in water (PO4 ^-)

Question 23

What are the properties of the 2 fatty acid tails?

Answer 23

Hydrophobic

They are non-polar regions

Question 24

What are uses for phospholipids?

Answer 24

Cell membranes - phospholipid bilayer

Question 25

What is formed when water is added to a phospholipid?

Answer 25

Micelle

Looks like a ring with the hydrophilic head on the outside and very inside
Leaving the hydrophobic tails on the inner forming an area of fatty acid tails with no water