Lesson 8/9 - Lipids - Triglycerides/phospholipids Flashcards
Lipids all share these characteristics:
● All contain the elements Carbon, Hydrogen and Oxygen
● They are non-polar molecules due to the large number of C’s & H’s and so are insoluble in water
● They are soluble in other organic solvents (eg. alcohols)
What are the 2 main groups of lipids?
● Triglycerides (the fats and oils) - a component of our diet
● Phospholipids - a component of cell membranes
How are triglycerides formed?
By the condensation of 1 molecule of glycerol and 3 molecules of fatty acid.
Which bond is created when glycerol bonds to a fatty acid (RCOOH) ?
Ester bond
Which group of a fatty acid can be saturated or unsaturated?
R group
What’s the difference between a triglyceride and a phospholipid?
In a phospholipid, 1 of the fatty acid’s of a triglyceride is substituted with a phosphate containing group.
What’s a fatty acid?
● Long hydrocarbon chain with a carboxylic acid group at one
end
● Some fatty acids contain carbon double bonds and some don’t
What’s the emulsion test for lipids?
- Mix the sample being tested with alcohol (eg. ethanol) in a test tube
- Shake the tube thoroughly
- Add cold water and shake gently
- If a milky-white emulsion is formed, this indicates the presence of a lipid
Whats the Difference between saturated and unsaturated fatty acids?
● Saturated fatty acids have only C-C so form linear hydrocarbon chains.
● Unsaturated fatty acids have one or more C=C which causes the hydrocarbon chain to bend.
Saturated definition
No double bonds between carbon atoms.
Mono-unsaturated definition
Contains 1 double bond between carbon atoms.
Polyunsaturated definition
More than 1 double bond between carbon atoms.
Patterns/formation of saturated and unsaturated fatty acids
● Saturated fatty acids fit closely together in a regular pattern.
● Unsaturated fatty acids push each other apart forming irregular patterns.
Properties of saturated fatty acids
● Contain only C-C bonds (and therefore form linear hydrocarbon chains)
● Fatty acids can pack closely together
● Strong attractions (intermolecular bonds) between fatty acid chains
● High melting points
● Solids at room temperature
Properties of unsaturated fatty acids
● Contain one or more C=C (causing the hydrocarbon chains to bend)
● The nonlinear chains do not allow the fatty acid molecules to pack closely together
● Weaker attractions (intermolecular bonds) between fatty acid chains
● Lower melting points
● Liquids at room temperature
Why are fats generally solid at room temperature?
Fats are generally made of saturated fatty acids hence why they are solid at room temperature.
Why are oils generally liquid at room temperature?
Oils are generally made of unsaturated fatty acids hence why they are liquid at room temperature.
Which term describes triglycerides being large, insoluble molecules?
Hydrophobic
What happens during condensation? (triglyceride)
● Produces a triglyceride
● Formed from a glycerol and 3 fatty acids
● 3 water molecules are released
● 3 ester bonds formed
What happens during hydrolysis? (triglyceride)
● Triglyceride is split by the addition of 3 water molecules
● 3 ester bonds broken
● Glycerol and 3 fatty acids are formed
Which intermolecular bonds in saturated and unsaturated fatty acids are stronger?
The intermolecular bonds between the saturated fatty acids are stronger than the ones between the unsaturated bonds, as they closer together.
Which part of a phospholipid is hydrophobic (repels water) and which is hydrophilic (attracts water) ?
hydrophobic (repels water) - fatty acid
hydrophilic (attracts water) - phosphate molecule
Which fatty acids does a phospholipid contain?
A saturated and an unsaturated fatty acid
How do phospholipids position themselves when placed in water?
So that the heads are as close to water as possible and the tails are as far from water as possible.
What are some roles of lipids?
● Lipids are a source of energy - provide more than double the energy as the same amount of carbohydrate
● Waterproofing (as they are hydrophobic) - waxy, lipid cuticles are found in both plants and insects to conserve water (reduce water loss)
● Insulation - fats are slow conductors of heat, so, a layer of fat stored under the skin helps to retain body heat (prevent it being lost)
● Protection - fat is often stored round delicate organs eg. the kidney, to protect from damage
● Buoyancy - slightly less dense than water
● Electrical insulator - surrounds nerves to increase the speed of electrical impulses
