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BIOC 2580 Study Guide - Phospholipid, Methyl Group, Glycerol


Department
Biochemistry
Course Code
BIOC 2580
Professor
E P Wijekoon

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BIOC 2580 Final Exam Notes
1. Lipids
Fatty Acids
Functions
Building blocks for complex lipids
Central intermediates in metabolism
Structure
Carboxylic acids with hydrocarbon chains (4-36carbons)
Most abundant fatty acids have even # of C atoms
Nomenclature
Can number carbons 1,2,3… starting with carboxylic acid
Can label in Greek α, β… starting at carbon to which the carboxylic acid group is bonded
Can identify C positions relative to terminal methyl carbon called ω
Hydrophobicity
Aggregate spontaneously when mixed in water to form complexes
Nature of aggregate depends on chemistry of lipid and environmental conditions (temp,
presence of other solutes
Miscelles: smallest and simplest of lipid aggregates
Diameters 3 – few hundred nm
Cause cloudy appearance
Typical Saturated Fatty Acids
Unsaturated Fatty Acids
Have one of more double bonds
Polyunsaturate fatty acids (PUFA): double bond separated by methylene carbon
Bond pattern: double- single- single- double
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Unsaturated double bonds naturally occur in cis conformation
Trans uncommon
Process of partial hydrogenation of oils (make them harder) can isomerize double bonds
Trans Fatty Acids
Trans double bond allows fatty acid to adopt extended conformation
Pack more regularly than cis bonds
Higher melting point
Nomenclature
Positions of double bonds specified relative to carboxyl carbon (C-1)
Superscript following Δ
Can specify double bonds relative to ω carbon
Used for fatty acids between 3rd and 4th C atoms from methylene C or between C6 and
C7 from methyl group
Properties
Determined by length and degree if unsaturation of hydrocarbon chain
Unsaturation lowers melting point/increases fluidity:
Saturated FA tightly packed – van der Waals interactions
Unsaturated FA have kinks from cis double bonds – weaker interactions
Water solubility decreases with:
Longer hydrocarbon chain
Fewer double bonds
Esters and Anhydrides
Esters: carboxylic acids combined with alcohols
Anhydrides: carboxylic acids combined with acids
Both formed by condensation reactions
Bonds can be hydrolyzed
Free fatty acids never stay very long in cells
Usually converted to esters or anhydrides
Triacylglycerols (TAGs, triglycerides)
Structure
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