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What are Lipids ?

Lipids are water-insoluble, organic molecules found in biological systems.

Define hydrophobic and amphipatic.

Hydrophobic= non-polar, amphipathic= containing both polar and non-polar groups.

What are the four main classification of lipids ?

Fatty acids, glyceride, Non-glyceride lipids, Complex lipids.

What will lipids dissolve in ? give example.

Non polar solvents e.g. diethylether.

List 4 lipid Functions.

Structural components of all biological membranes. Effective means of storing energy. Provide insulation and protection. Provide hormones and fat-soluble vitamins.

What s a fatty acid composed of.

A long hydrocarbon tail bonded to a carboxylic acid group. Differ based on presence/absence of carbon-carbon double bonds and there position.

Two types of fatty acids are ?

Saturated fatty acids(General formula CH3(CH2)nC00H) each carbon bonded to the maximum number of hydrogen atoms. And unsaturated fatty acids general formula; CH3(CH2)nCH=CH(CH2)nC00H have one C=C or more.

General features of fatty acids are.

The pKa of the carboxylic acid group(-COOH) is approximately 4.5. The number of carbon atoms ranges from 12-22 and if normally a even number. The configuration of double bonds in a unsaturated fatty acid is normally "cis" put a kink in the tail of the unsaturated fatty acid.

Melting points of fatty acids;

Melting point increases as the number of carbons in the fatty acid increases. Why, Van der Walls forces increases as the number of atoms increases. Thus, more energy need to disrupt these forces.

Geometric Isomers

The C=C is rigid and so free rotation of the C-H moiety is not possible under normal conditions.

What is esterification ?

a fatty acid reacts with an alcohol to form an ester and water(for example the esterification of glycerol and fatty acids to form glycerides. e.g. R-COOH(acid)+ R-OH = R-COO-R(ester) + H2O.

Hydrolysis is ?

an ester is cleaved to yield a fatty acid and alcohol. This reaction is the reverse esterification and is catalysed by lipases, enzymes that release fatty acids from the body's glycerides stores when energy is required. R-COO-R(ester)+H2O = R-COOH(acid) +R-OH(alcohol)

What is acid-base reaction reactions(saponification)

A fatty acid will react with a base to yield a salt and water.( Soap and emulsifying) R-COOH(acid) + NaOH(base) = R-COO Na+(salt(Soap) + H2O

What is Hydrogenation ?

THis reaction involves addition of hydrogen to the double bond(s) of unsaturated fatty acids. It is widely used in the food industry; for example, hydrogenation of fatty acids in vegetable oil allows the production of spreads(margarines) that are solid at room temperature.

CH3(CH2)4CH=CH CH2 CH=CH(CH2)7COOH Linoleic acid(two cis C=C)

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