Lipids Flashcards
Lipid properties
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
Roles of Lipids
Contribute to the flexibility of cell membranes
Source of energy
Waterproofing
Insulation
Protection
Triglycerides
3 Fatty Acids & 1 Glycerol (condensation reaction)
Glycerol + 3 Fatty acids = Triglyceride + 3H2O
An ester bond is formed between COOC
Fatty Acids
COOH - R
COOH = Carboxylic acid group
R = Hydrocarbon Chain
O
II OH - C - R = 1 Fatty Acid
Glycerol
H
3 Carbons. I
H - C - OH
3 OH. H - C - OH
5 Hydrogens. H - C - OH
I
H
Triglyceride Functions and Adaptation
Contains lots of carbon - hydrogen bonds which makes them an excellent source of energy
Triglyceride functions and adaptation
Low mass to energy ratio which makes them good for storage as much energy can be stored in a small volume
Triglyceride Function and Adaptation
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
Triglyceride Function and Adaptation
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
Fatty Acids : Saturated
Saturated fatty acids have only single bonds between carbons in the hydrocarbon chain
Fatty Acids : Unsaturated
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
Phospholipids
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
⭕️〰️〰️
Phospholipid Bonding
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
Phospholipid Hydrolysis
Phospholipid + 3H2O —> Glycerol + 2 fatty acids + phosphate
Hydrophilic Head and Hydrophobic Tails
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
Why is water a polar molecule
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
Phospholipids + Water
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
Lipid hydrolysis
Lipase enzyme
Acid/Alkali
Triglyceride + 3H2O —> Glycerol + 3 Fatty acids
Phospholipid + 3H2O —> Glycerol + 2 Fatty Acids + Phosphate
Similarities/Differences
Triglycerides + Phospholipids
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
Test for lipids : Emulsion Test
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
