Lipids And Membranes - OCR

Revision notes on lipids and membranes for the Biochemistry module of A2 Chemistry.

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Lipids and Membranes
Tri ­ Ester ­ Fats
Ester = Carboxylic acid + Alcohol
= RCOOR'
The acids in Triglycerides are called fatty acids as some are vast in size
E.g. C15H31COOH or CH3(CH2)14COOH ­ Palmitic acid
Some fatty acids contain C=C double bonds
o Alkanes are saturated C­C
o Alkenes are unsaturated C=C
Therefore fatty acids containing C=C bonds are unsaturated
By eating Poly-Unsaturated fats not as much celesterol is made in the body
Functions of Fat
1. Secondary energy storage (Glycogen is primary storage)
2. Thermal insulation and Buoyancy
3. Making Membranes
Hydrolysis of Ester
1) Enzyme ­ Lipase turns fats into glycerol and fatty acids
2) Acidic Hydrolysis ­ Glycerol and Fatty Acids are formed
3) Alkaline Hydrolysis ­ Glycerol and Salt of Carboxylic acid is formed
E.g. Product can be R­COO­Na+ (soap)
R­COOH + NaOH R­COONa + H2O
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Why Triglycerides cannot dissolve in water
As C and H have nearly the same electronegativity they are none polar so won't dissolve in
water
1. The R groups are non polar
2. R groups therefore cant form H bonds with water
3. Non-Polar can only form Van de Waal forces
4. Fats will only dissolve in other non-polar substances
Phosphoglycerides
What happens in water?
1) Formation of a mono-layer
2) Formation of a Bi-molecular Layer
3) Formation of a `Miecelle'
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Energy Consideration
Carbohydrates are used for energy before fats
o can be accessed more quickly
o glucose can be hydrolysed anaerobicaly
lactic acid made
fats cannot be broken down anaerobicaly
Fats produce twice as much energy per gram compared to glucose
Example exam Q.
Q.…read more

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