These extensive notes are based on the BCM 261 lecture notes and Lehninger Principles of Biochemistry textbook. The notes cover all the work in the module and have also been double checked using the learning outcomes in the study guide to ensure all the information was there. They also include all ...
Chapter 10 (page 361-366)
Classification of lipids
• Lipids: a heterogeneous class of naturally occurring organic compounds classified together
on the basis of common solubility properties
• Insoluble in water, but soluble in organic solvents
• Often amphipathic in nature
Biological functions of lipids
Storage of energy
• Reduced compounds: lots of available energy
• Hydrophobic nature: good packing
,Insulation from environment
• Low thermal conductivity
• High heat capacity (can ‘absorb’ heat)
• Mechanical protection (can absorb shocks)
Water repellent
• Hydrophobic nature: keeps the surface of the organism dry
• Prevents excessive wetting (birds)
• Prevents loss of water via evaporation
Buoyancy control and acoustics in marine mammals
• Increased density while diving deep helps sinking (just a hypothesis)
• Spermaceti organ may focus sound energy: sound stun gun?
More functions
Membrane structure
• The main structure of cell membranes
Cofactors for enzymes
• Vitamin K: blood clot formation
• Coenzyme Q: ATP synthesis in mitochondria
Signalling molecules
• Paracrine hormones (act locally)
• Steroid hormones (act body-wide)
• Growth factors
• Vitamins A and D (hormone precursors)
Pigments
• Colour of tomatoes, carrots, pumpkins, some birds
Antioxidants
• Vitamin E
,Classification of lipids
Two major categories based on the structure and function
Lipids that contain fatty acids
(complex lipids)
Can be further separated into:
• Simple lipids (storage lipids)
• Complex lipids (membrane lipids)
Derived lipids
• Lipids that do not contain fatty
acids: cholesterol, vitamins, pigments,
etc.
• Formed from C-atoms derived from
fatty acids
Fatty acids
• Carboxylic acids with hydrocarbon chains
containing between 4 to 36 carbons
• Almost all natural fatty acids have an even
number of carbons.
• Most natural fatty acids are unbranched
Saturated fatty acids
• Saturated: no double bonds between
carbons in the chain
• In this course, we will draw the structures
without the C and H atoms of the
hydrocarbon chain-zig-zag structures
Fatty acid nomenclature
• Know the common names for the fatty acids, not the systematic names, with the
corresponding shorthand nomenclature (carbon skeleton)
• From this, you can derive the structure
• Need to know that the melting point increase with increasing C-length, not the actual value
• Melting points increase with an increase in the number of C-atoms (stronger hydrophobic
interactions)
Unsaturated fatty acids
• Monounsaturated: one double bond between carbons in the alkyl chain
• Polyunsaturated: more than one double bond in the alkyl chain
• Melting points decrease with an increase in the number of double bonds (unsaturation)
(liquids at room temperature)
• Vegetable fats: polyunsaturated fatty acids > saturated fatty acids (liquids)
• Animal fats: saturated fatty acids > polyunsaturated fatty acids (solids)
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