3.1.3 LIPIDS

Question 1

What do lipids contain?

Answer 1

Carbon
Hydrogen
Oxygen

Question 2

Are lipids soluble or insoluble in water?

Answer 2

Insoluble
Non- polar and hydrophobic

Question 3

Two groups of lipids:

Answer 3

1. Triglyceride (main component of fats + oils)
2. Phospholipids

Question 4

Monomers of triglycerides;

Answer 4

Glycerol and three fatty acids

Question 5

What are lipids?

Answer 5

NOT polymers

Question 6

What are fats soluble in?

Answer 6

Organic solvents such as alcohols- why the lipid emulsion test works

Question 7

How are triglycerides formed?

Answer 7

• condensation reaction
• ester bond (a covalent bond) forming between glycerol + fatty acids
• hydrolysis forms glycerol + fatty acids
• 3 molecules of water produced

Question 8

Roles of triglycerides:

Answer 8

• protection of organs
• cell membranes
• insulation
• buoyancy
• energy store

Question 9

Structure VS function of a triglyceride:

Answer 9

Structure: more CH bonds
Function: energy store

Question 10

Fats are components of cell membranes….

Answer 10

They add flexibility and allow soluble substances to cross them

Question 11

Fats are a source of energy….

Answer 11

When oxidised they provide twice the energy for the same mass if carbs aswell as releasing more water in the process

Question 12

Fats can be used for waterproofing…

Answer 12

They are insoluble in water which is why plants and insects have waxy lipid cuticles and animals such as penguins secrete oils

Question 13

Saturated fatty acids do not contain…

Answer 13

A carbon- carbon double bond
Therefore, the hydrogen is saturated

Question 14

Saturated fatty acids don’t contain…

Answer 14

A carbon- carbon double bond
Therefore, the hydrogen is saturated

Question 15

Unsaturated fatty acids do contain…

Answer 15

Carbon=carbon double bonds
They cause the hydrocarbon chain to bend/kink

Question 16

What do fatty acids contain?

Answer 16

• a methyl group at one end of a hydrocarbon chain known as the “R” group
• at the other end is a carboxyl group

Question 17

The shorthand chemical formula for a fatty acid is…

Answer 17

RCOOH

Question 18

How do fatty acids vary?

Answer 18

• length of hydrocarbon chain (R group)
• fatty acid chain (R group) may be saturated or unsaturated

Question 19

How do unsaturated fatty acids vary?

Answer 19

Can by mono or poly-unsaturated

Question 20

How many fatty acids are bonded to a glycerol molecule in a phospholipid?

Answer 20

Two fatty acids joined to a glycerol molecule because one has been replaced by a phosphate ion

Question 21

Is the phosphate ion in a phospholipid soluble in water?

Answer 21

Yes, as it is polar
It is hydrophilic

Question 22

Are the fatty acids tails in a phospholipid soluble in water?

Answer 22

• No, they are non- polar
• They are Hydrophobic

Question 23

Phospholipids are ……….. (they have both hydrophobic and hydrophilic parts)

Answer 23

Amphipathic
- as a result of having both parts, phospholipid molecules form monolayers or bilayers in water

Question 24

Role of phospholipids:

Answer 24

Main component of cell membranes

Question 25

What is created due to the presence of hydrophobic fatty acid tails when a phospholipid bilayer forms?

Answer 25

• hydrophobic core
• acts as a barrier to water- soluble molecules