LiroxtronIV (LiroxtronIV)-
Describe the test for fats.
Emulsion test
1. Add 2cm3 of sample into test tube containing 2cm3 of ethanol.
2. Shake the mixture well.
3. Allow mixture to settle for 2 minutes.
4. Empty any clear liquid into a test tube containing 2cm3 of water.
(lipids soluble in ethanol, dissolve to make up clear liquid. when mixed with water lipid molecules clump together to form white emulsion)
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Describe difference between saturated & unsaturated fatty acids.
saturated - in H atoms, unsaturated - lacking H atoms
unsaturated - presence of C=C double bonds results in presence of kinks in fatty acid tails -> molecules pack less closely together, weaker hydrophobic interactions between fatty acid tails and require less heat to be disrupted.(compared to saturated)
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Describe formation of ester bond.
An ester bond is formed between one -OH group of glycerol and the -COOH group of a fatty acid, in a condensation/esterification reaction with the removal of a water molecule, catalysed by enzymes.
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Describe breakage of ester bond.
An ester bond is broken between one -OH group of glycerol and the -COOH group of a fatty acid by the addition of an acid/base, in a hydrolytic reaction(saponification) with the addition of a water molecule, catalysed by enzymes.
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Relate structure to function; triglycerides.
higher proportion of H and almost insignificant proportion of O compared to carbs; higher ratio of energy storing C-H bonds to carbon atoms than carbs
-> when given mass of triglycerides oxidised during respiration, >2x amount of energy is released in the form of ATP than same mass of carbs
-> good energy source
contain more energy/g than carbs and proteins, provides the most weight-efficient means for plant/animal to store energy.
-> good energy storage molecule
large molecules, non-polar; insoluble in water.
->won't diffuse out of cell nor change water potential in cell, can be stored in large amounts in cell
-> good energy storage molecule
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Describe structure of phospholipids.
2 ester bonds formed between 2 -OH groups of glycerol and a -COOH group from 2 fatty acids, 1 phosphodiester bond formed between 1 -OH group of glycerol and phosphate group of phosphoric acid, in condensation reactions.
Fatty acid tails are non-polar and hydrophobic, phosphate group is polar and hydrophilic - phospholipid is amphipathic in nature.
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Relate structure to function; phospholipids.
polar hydrophilic phosphate head face outwards, non-polar hydrophobic fatty acid tails face inwards. phospholipids align; non-polar fatty acid tails buried inside 2 layers of polar phosphate heads, forming phospholipid bilayer
-> compartmentalisation of cell(cell membrane)
-> selective barrier; hydrophobic core restricts movement of polar molecules/charged ions across membrane
-> membrane fluidity; phospholipids held by weak hydrophobic interactions- can diffuse rapidly within their own layers, forming transient pores. kinks in unsaturated fatty acid tails prevent packing closely together, enhances membrane fluidity.
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Relate structure to function; triglycerides(animals).
(ARID ANIMALS)
>proportion of H than carbs
-> when oxidised, given mass of triglycerides produce more metabolic water per gram than same mass of carbs
-> water retained in desert animals which help them survive in arid environment
-> source of (metabolic) water
(ARCTIC ANIMALS)
good thermal insulators, conduct heat slowly; reduces heat loss from body
-> good thermal insulation for animals in cold climates
(SEA ANIMALS)
less dense than H2O
-> confer buoyancy
