Lipids

Question 1

Lipid properties

Answer 1

2 Types : Tryglycerides and Phospholipids
Fats (solids) / Oils (liquids)
Fatty acids and glycerol
Lipase enzymes
Long term energy store
Insulation
Waxy layer —> reduce water loss
Insoluble in water
Soluble in other solvents eg alcohol
Produce metabolic water when respiration occurs
Structural - Cell membrane

Question 2

Roles of Lipids

Answer 2

Contribute to the flexibility of cell membranes
Source of energy
Waterproofing
Insulation
Protection

Question 3

Triglycerides

Answer 3

3 Fatty Acids & 1 Glycerol (condensation reaction)
Glycerol + 3 Fatty acids = Triglyceride + 3H2O
An ester bond is formed between COOC

Question 4

Fatty Acids

Answer 4

COOH - R
COOH = Carboxylic acid group
R = Hydrocarbon Chain

    O
     II OH - C - R    = 1 Fatty Acid

Question 5

Glycerol

Answer 5

H
3 Carbons. I
H - C - OH
3 OH. H - C - OH
5 Hydrogens. H - C - OH
I
H

Question 6

Triglyceride Functions and Adaptation

Answer 6

Contains lots of carbon - hydrogen bonds which makes them an excellent source of energy

Question 7

Triglyceride functions and adaptation

Answer 7

Low mass to energy ratio which makes them good for storage as much energy can be stored in a small volume

Question 8

Triglyceride Function and Adaptation

Answer 8

Large, non-polar molecules which makes them insoluble so there storage does not affect osmosis
Won’t cause too much water to move into the cell so the cell won’t burst

Question 9

Triglyceride Function and Adaptation

Answer 9

High ratio of hydrogen to oxygen atoms
Triglycerides release water when oxidised so they provide an important source of water especially for organisms in dry deserts
they act as a metabolic water source

Question 10

Fatty Acids : Saturated

Answer 10

Saturated fatty acids have only single bonds between carbons in the hydrocarbon chain

Question 11

Fatty Acids : Unsaturated

Answer 11

Have at least one double bond between carbons in the hydrocarbon chain therefore not holding the maximum number of hydrogen atoms as possible as the bond forms between the carbons and 1 less hydrogen is there

Question 12

Phospholipids

Answer 12

1 Glycerol
2 Fatty Acids
1 Phosphate
Fatty Acids are hydrophobic (repel water)
Phosphate molecules are hydrophilic (attract water)
Charged (hydrophilic) head
Non Polar (hydrophobic) tails
⭕️〰️〰️

Question 13

Phospholipid Bonding

Answer 13

2 fatty acids bond to the glycerol via 2 condensation reactions resulting in 2 ester bonds
Ester bond is the oxygen between the carbons
glycerol + 2 fatty acids + phosphate —> phospholipid + 3H2O

Question 14

Phospholipid Hydrolysis

Answer 14

Phospholipid + 3H2O —> Glycerol + 2 fatty acids + phosphate

Question 15

Hydrophilic Head and Hydrophobic Tails

Answer 15

Hydrophilic ‘head’ of a phospholipid can attract with water as it has a negative charge
Due to the phosphate being charged, it repels other fats
The fatty acid chain is not charged it is known as the hydrophobic ‘tail’ and jt repels water but will mix with fats

Question 16

Why is water a polar molecule

Answer 16

Because oxygen and hydrogen have different electro negativity value
Oxygen has 2 lone electron pairs that repel each other and the electrons bonded to the hydrogen atoms
This gives water molecule a bent shape
Oxygen side has a partial negative charge
Hydrogen side has a partial positive charge

Question 17

Phospholipids + Water

Answer 17

Phospholipids in water create a phospholipid bilayer (2 layers)
Double layer of phospholipids where the tails face each other inwards because they’re repelled by water
Hydrophilic heads move on the outside because they can interact with water
Phospholipids are polar because they have 2 charged regions

Question 18

Lipid hydrolysis

Answer 18

Lipase enzyme
Acid/Alkali

Triglyceride + 3H2O —> Glycerol + 3 Fatty acids
Phospholipid + 3H2O —> Glycerol + 2 Fatty Acids + Phosphate

Question 19

Triglycerides + Phospholipids

Answer 19

Similarities:
- Both insoluble in water
- Both contain glycerol
- Both contain ester binds
- Both contain C H O

Differences :
- Triglycerides have 3 fatty acids
-Phospholipids have 2 fatty acids + phosphate group
-Triglycerides are hydrophobic/non-polar
- Phospholipids have hydrophobic and hydrophilic regions

Question 20

Test for lipids : Emulsion Test

Answer 20

1) Add a small amount of the sample into a test tube with ethanol
2) Shake the mixture so that the fat dissolves
3) Add this to water in another test tube and mix
4) A white emulsion of fat droplets indicated lipid is present