Lipids

Question 1

What are lipids used for?

Answer 1

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

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 is the general formula of a fatty acid?

Answer 7

RCOOH

O
||
R-C-O-H

Question 8

What are the two types of fatty acids?

Answer 8

Saturated

Unsaturated

Question 9

What are the properties of saturated fatty acids?

Answer 9

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

Question 10

What are the properties of unsaturated fatty acids?

Answer 10

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

Question 11

What are the different names for unsaturated chains?

Answer 11

Monosaturated (1 c=c)

Polyunsaturated (+1 c=c)

Question 12

What is the structure of glycerol?

Answer 12

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

Question 13

What reaction forms a triglyceride?

Answer 13

Condensation reaction

Question 14

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

Answer 14

Ester bond

3 bonds

Question 15

What are the products are formed in a condensation reaction?

Answer 15

1 triglyceride molecule

3 waters

Question 16

What are the uses of triglycerides?

Answer 16

Energy rich - high ratio of C-H bonds

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

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

Question 17

What is the test for lipids?

Answer 17

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 18

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

Answer 18

You are putting two immiscible liquids together forming an emulsion

Question 19

What is another type of lipid?

Answer 19

Phospholipid

Question 20

How is the structure of a phospholipids different?

Answer 20

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

Question 21

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

Answer 21

Hydrophilic

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

Question 22

What are the properties of the 2 fatty acid tails?

Answer 22

Hydrophobic

They are non-polar regions

Question 23

What are uses for phospholipids?

Answer 23

Cell membranes - phospholipid bilayer

Question 24

What is formed when water is added to a phospholipid?

Answer 24

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

Question 25

Why are unsaturated fats liquids not solids at room temperature?

Answer 25

Because they have double carbon carbon bonds making it bend so it’s less dense because less chains are packed together

Question 26

What is the difference between a monounsaturated fat and a polyunsaturated fat?

Answer 26

The number of carbon carbon double bonds

Question 27

Why are fats suitable as an energy store?

Answer 27

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