What characteristics do all lipids share?
- contain Carbon, hydrogen & oxygen
- non-polar molecules - due to large no. C’s and H’s so - insoluble in water
- soluble in other organic solvents e.g. alcohols
2 main groups of lipids and what are they a component of ?
Triglycerides (fats & oils) - component of our diet
Phospholipids - component of cell membranes
- both contain glycerol molecule & fatty acids
- tri: 3 fatty acids chain
- phospho: 2 chains instead of 3rd replaced by phosphate group
How are triglycerides formed?
- via the condensation between 1 molecule of glycerol & 3 molecules of fatty acid - 3 separate condensation reactions
- each of the chains go through condensation reactions w glycerol so - 3 water molecules produced & 3 ester bonds forming
What are fatty acids?
- long hydrocarbon chain w a carboxylic acid group at one end & methyl group on other
- some contain C double bonds, some don’t
- AKA R group because: no. of Cs & Hs can vary (R = variable group)
What are the 2 types of fatty acids?
Saturated: have only C-C (single bonds between carbons) so form linear hydrocarbon chains
Unsaturated: have 1 or more C=C (double bond between carbons) which causes the hydrocarbon chain to bend
What is the result of having the C-C & C=C?
- saturated fatty acids fit closely together in a regular pattern
- unsaturated fatty acids push e/o apart forming irregular patterns
Properties of saturated fatty acids?
- contain only C-C bonds - form linear hydrocarbon chains
- fatty acids can pack closely together
- strong attractions (intermolecular bonds) between fatty acid chains
- high mps
- solids at room temp
- e.g. fats
Properties of unsaturated fatty acids?
- contain 1 or more C=C - hydrocarbon chains bend
- these non-linear chains don’t allow fatty acid molecules to pack closely together
- weaker attractions (intermolecular bonds) between fatty acid chains
- lower mps
- liquid at room temp
- e.g. oils
Properties of triglycerides (due to structure)?
- Energy storage: due to large ratio of energy-storing carbon-hydrogen bonds compared to no. C atoms - lot
- Metabolic water source: due to high ratio of H atoms compared to O atoms aka can release water if oxidised (essential for animals in desert e.g. camels)
- Don’t affect water potentials & osmosis -large & hydrophobic so - insoluble in water
- Relatively low mass so - stored w/o increasing mass & preventing movement
Differences between the condensation & hydrolysis of triglycerides?
Condensation:
- produces a triglyceride
- formed from glycerol + 3 fatty acids
- 3 water molecules released
- 3 ester bonds formed
Hydrolysis:
- triglyceride split by addition of 3 water molecules
- 3 ester bonds broken
- glycerol + 3 fatty acids formed
Phospholipids?
- made of: glycerol molecule, 2 fatty acid chains + phosphate group (attached to glycerol)
- 2 fatty acids also bond to glycerol via 2 condensation reaction - 2 ester bonds
Properties of phospholipids?
- the hydrophilic (can attract + interact w water) head of a phospholipid can attract water - it’s charged
- due to phosphate being charged - repels other fats
- fatty acid chain isn’t charged aka hydrophobic tail - repels water but mixes w fats
Result of properties of phospholipids?
- hv 2 charged regions so -polar
- in water: positioned so heads are exposed to water (as close as poss) & tails are not (as far as poss)…
- forms a phospholipid bilayer membrane structure - makes up the plasma membrane around cells
