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Biochemistry Review Chapters 10, 13, 14, & 15
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Biochemistry Review Chapters 10, 13, 14, & 15 Biochemistry Review Chapters 10, 13, 14, & 15 Biochemistry Review Chapters 10, 13, 14, & 15
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Biochemistry Review Chapters: 10, 13, 14, & 15Chapter 10: Lipids
• Biological Functions of Lipids:
o Storage of energy
▪ Reduced compounds: lots of available energy
▪ Hydrophobic nature: good packing
o Insulation from environment
▪ Low thermal conductivity
▪ High heat capacity (can “absorb” heat)
▪ Mechanical protection (can absorb shocks)
o Water repellant
▪ Hydrophobic nature: keeps surface of the organism dry
• Prevents excessive wetting (birds)
• Prevents loss of water via evaporation
o 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:
o Membrane structure
▪ Main structure of cell membranes
o Cofactors for enzymes
▪ Vitamin K: blood clot formation
▪ Coenzyme Q: ATP synthesis in mitochondria
o Signaling molecules
▪ Paracrine hormones (act locally)
▪ Steroid hormones (act body-wide)
▪ Growth factors
▪ Vitamins A and D (hormone precursors)
o Pigments
▪ Color of tomatoes, carrots, pumpkins, some birds
• Depending on wave lengths is what gives off color
o Antioxidants
▪ Vitamin E
• Classification of lipids:
o Based on the structure and function
▪ Lipids that do not contain fatty acids: cholesterol, terpenes,…
▪ Lipids that contain fatty acids (complex lipids)
• Can be further separated into
o Storage lipids and membrane lipids
,• Fatty Acids:
o Complete oxidation to CO2 and H2O
o Carboxylic acids with hydrocarbon chains containing between 4 to 36 carbons
▪ Even #-- every acetyl group
▪ Almost all natural fatty acids have an even number of carbons
▪ Most natural fatty acids are unbranched
▪ Saturated: no double bonds between carbons in the chain
▪ Monounsaturated: one double bond between carbons in the alkyl chain
▪ Polyunsaturated: more than one double bond in the alkyl chain
▪ May contain ring structures
o Chain length: number of double bonds
• How many carbons
• Where the double bonds reside
▪ Double bond position given by a Δ followed by the number of the
carbon, which is participating in the double bond. Note that the
carboxyl group carbon is C-1
o Solubility and Melting point of fatty acids:
▪ Solubility (largely determined by chain length and degree of saturation of the
hydrocarbon chain)
▪ Decreases as the chain length increases
▪ Longer fatty acid chain
• Decrease solubility
• Increase melting point
▪ Shorter fatty acid chain
• Increase solubility
• Decrease melting point
▪ Fewer double bonds, less soluble
▪ Melting Point (Influenced by length and degree of unsaturation of the
hydrocarbon chain)
• Decreases as the chain length decreases
• Decreases as the number of double bonds increases
• At room temp the saturated fatty acids from 12:0 to 24:0 are
waxy while the corresponding unsaturated fatty acids are oily
liquids
• Differences due to the degree of packing of the molecules
• For saturated fatty acids melting point increases
• Longer chain- increase
• Double bond present- dramatically decrease melting point
o Saturated fatty acids pack in a fairly orderly way
▪ Extensive favorable interactions
o Unsaturated cis fatty acid pack less orderly due to the kink
▪ Less-extensive favorable interactions
o It takes less thermal energy to disrupt disordered packing of unsaturated fatty acids:
▪ Unsaturated cis fatty acids have a lower melting point
o Trans fatty acids can pack more regularly and show higher melting points than cis forms
• Triacylglycerols:
o In vertebrates, free fatty acids with a free carboxylate
group are bound to a protein carrier called serum albumin
o Majority of fatty acids in biological
systems are found in the form of
triacylglycerols
o Solid ones are called fats, liquid ones are called oils
, o The primary storage form of lipids (body fat)
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