Lipids

Question 1

How do triglycerides form?

Answer 1

Condensation reaction between 1 glycerol molecule & 3 fatty acids.

Forms 3 ESTER bonds and 3 WATER molecules.

Question 2

Draw the structure of a glycerol and fatty acids.

Answer 2

Glycerol:
- 3 central carbons
- each bonded to OH
- bonded to hydrogen on other sides

Fatty acids: (contains a carboxylic group)
- central carbon
- C bonded to OH
- C=O bond
- C bonded to R group

Question 3

Uses of fats/lipids?

Answer 3

Energy sources
Insulator - contains layers - retains heat
To protect organs.
To produce cell membranes (phospholipids)

Question 4

What is the condensation reaction to produce triglycerides?

Answer 4

Glycerol + 3 fatty acids —> Triglyceride + 3 water molecules

It forms 3 ester bonds (-COO groups)

Question 5

Draw the structure of triglycerides.

Answer 5

Triglycerides:

(Draw a glycerol molecule)
Remove the H+ ion from OH and connect the O with the central carbon from fatty acids.

The ESTER bond is the whole -COO group produced.

Question 6

What are the features of saturated fatty acids?

Answer 6

~ Contains ONLY single carbon-carbon bonds. (C-C)
~ Straight-chain molecules.
~ More viscous

~ Higher melting point = solid at room temp.
~ Found in animal fats.

Question 7

What are the features of unsaturated fatty acids?

Answer 7

~ Contains DOUBLE bonds between carbon (C=C)
~ ‘Kinked’ molecules.
~ Less viscous

~ Lower melting point = liquid at room temperature.
~ Found in plant oils.

Question 8

Give some examples of saturated and unsaturated fats.

Answer 8

SATURATED =
Milk & butter

UNSATURATED =
Olive oil

Question 9

Relate the structure of triglycerides to their functions.

Answer 9

Non-polar molecule = hydrophobic = insoluble
no affect on water potential (used for waterproofing)

Releases a lot of ENERGY =
High number of C & H atoms - good storage and source of water via respiration.

LARGE = makes it good storage molecule.- can’t leave cell

Slow conductor of heat = (thermal insulation)

Less dense than water = (buoyancy of aquatic animals)

Question 10

Relate the structure of phospholipids to their functions.

Answer 10

Amphipathic molecule =
Glycerol backbone attached to 2 HYDROPHOBIC fatty acid tails & 1 HYDROPHILIC phosphate head.

Amphipathic = forms phospholipid bilayer in water =
makes up cell membranes

Tails can splay outwards =
waterproofing

Question 11

Draw the structure of a phospholipid molecule.

Answer 11

Same thing as a triglyceride… EXCEPT

First carbon bonded with a phosphate group.
Phosphate group has a central phosphorus and 4 oxygen atoms (one double bond)
The top and bottom oxygen atoms are negatively charged.

2nd & 3rd carbon attached to 2 fatty acid chains.

Question 12

How are phospholipids formed?

Answer 12

Condensation reaction between glycerol molecule, 2 fatty acid chains AND 1 phosphate group.

Forms 2 ester bonds AND 2 water molecules.

Question 13

What does a hydrophilic head do?

Answer 13

Will be attracted to and interacts with water because they have a charge.

Repels fats & oils.

Question 14

What does a hydrophobic tail do?

Answer 14

Repels water because they do not have a charge.

Interacts with fats & oils.

Question 15

What does a monounsaturated fatty acid mean?

Answer 15

There is only 1 C=C bond.

Question 16

What does a polyunsaturated fatty acid mean?

Answer 16

2 or more C=C bond is formed.

Question 17

What is the common abbreviation for fatty acids?

Answer 17

RCOOH

Question 18

What are lipids?

Answer 18

Macromolecules made from small, different sized molecules joined together.

It is NOT a polymer.

Question 19

Why are saturated fatty acids solid at room temperature?

Answer 19

Straight, parallel hydrocarbon chain don’t take up a lot of space and can be packed tightly together - forms solid at room temp.

Compact.

Question 20

Why are unsaturated fatty acids liquid at room temperature?

Answer 20

Have bends/kinks in hydrocarbon chains, so it takes lots of space and can’t be packed tightly together, forming a liquid at cool temperatures.

Not compact.

Question 21

Why does oil not mix with water?

Answer 21

Polar molecules do NOT mix with non-polar molecules.

Water is polar and triglycerides in oil is non-polar (insoluble - hydrophobic)

Question 22

Where are the polar and non-polar regions of a triglyceride?

Answer 22

Carboxyl group is polar (partially positive & partially negative)

Hydrocarbon chain of fatty acids is non-polar.

Question 23

What does amphipathic mean?

Answer 23

(of a molecule, especially a protein) having both hydrophilic and hydrophobic parts.

Question 24

Describe the emulsion lipid test.

Answer 24

1~ Dissolve solid sample in ethanol and mix.
2~ Add an equal amount of water and shake gently.

Positive result: white, milky emulsion formed.

Question 25

Are triglycerides and phospholipids polymers?

Answer 25

NO - they are macromolecules

They aren’t made from a repeating unit.

Question 26

What is the name of the process where an ester bond is produced?

Answer 26

Esterification

Question 27

What are the hydrophobic and hydrophilic parts of a phospholipid?

Answer 27

We have…

Polar hydrophilic head

Non-polar hydrophobic tails

As the head goes outwards and the tails go inwards, it forms a phospholipid BILAYER.