Lipids

Question 1

What are lipids?

Answer 1

Lipids are a diverse group of compounds that are insoluble
in water but soluble in organic solvents such as ethanol.

Question 2

What type of reaction do fatty acids and glycerol undergo to become triglycerides?

Answer 2

Condensation

Question 2

What is the most common Type of lipid?

Answer 2

The most common types
of lipid are triglycerides
(sometimes known as true
fats or neutral fats)

Question 2

What are some examples of lipids

Answer 2

other important lipids
include waxes, steroids
and cholesterol

Question 2

What are the triglycerides made from?

Answer 2

Triglycerides are organic molecules made up
of three fatty acids and one glycerol
molecule

Question 3

What are the bonds formed between the fatty acids and glycerol?

Answer 3

Ester

Question 4

What are Saturated Fats? structural properties of them.

Answer 4

Saturated fatty acids contain only single carbon-carbon covalent
bonds

In saturated fatty acids, the hydrocarbon chain is long and
straight.

The saturated chains can pack closely together.

There are many intermolecular forces between triglycerides and so
saturated fats are solids are room temperature.

 C – C single bond
 No kinks within chains
 Solid at room temperature
 High melting point
 E.g. animal fat/lard

Question 5

What are Unsaturated Fats? structural properties of them.

Answer 5

 Unsaturated fatty acids contain at least one
carbon-carbon double bond.

 A monounsaturated fatty acid has one carbon
carbon double bond.

 A polyunsaturated fatty acid has more than one
C-C double bond.

unsaturated fatty acids
 C = C double bonds
 Kinks within chains
 Liquids at room temperature
 Low melting point
 E.g. olive oil

Question 6

What is the major role of lipids and why?

Answer 6

The major biological role of lipids is as an energy source.
Lipids provide more than twice the amount of energy as
carbohydrates – about 38 kJ/g.

Question 7

What are the major roles of lipids? (7)

Answer 7

More uses of lipids
 Energy storage – twice as much as carbohydrates. Lipids are
insoluble, compact and minimise mass.
 Protection – form protective layer around organs.
 Waterproofing – skin, fur, feather all contain lipids that are
hydrophobic to repel water.
 Insulator – heat insulation to prevent heat loss.
 Buoyancy – lipids are less dense than muscle and water and
allow organisms to float.
 Membrane fluidity – tied with the fluid mosaic model and
membrane fluidity due to cholesterol.
 Cell membranes – phospholipids

Question 8

What test do we do for lipids?

Answer 8

Emulsion test, emulsion with ethanol

Question 9

How to carry out the test for lipids?

Answer 9

Dissolve in ethanol as they are both non-polar, then the dissolved lipid is added to pure water,which is insoluble which forming a cloudy emulsion