Theme 1: lipid metabolism
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
, Some naturally occurring fatty acids: structure, properties, and nomenclature
Carbon Common name Melting
Structure Systemic name
skeleton (derivation) point (˚C)
n-Dodecanoic
12:0 CH3(CH2)10COOH Lauric acid (laurel plant) 44.2
acid
n-Tetradecanoic Myristic acid (nutmeg
14:0 CH3(CH2)12COOH 53.9
acid genus)
n-Hexadecanoic
16:0 CH3(CH2)14COOH Palmitic acid (palm tree) 63.1
acid
n-Octadecanoic
18:0 CH3(CH2)16COOH Stearic acid (hard fat) 69.6
acid
Arachidic acid (legume
20:0 CH3(CH2)18COOH n-Eicosanoic acid 76.5
genus)
n-Tetracosanoic Lignoceruc acid (wood
24:0 CH3(CH2)22COOH 86.0
acid and wax)
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)
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
, Some naturally occurring fatty acids: structure, properties, and nomenclature
Carbon Common name Melting
Structure Systemic name
skeleton (derivation) point (˚C)
n-Dodecanoic
12:0 CH3(CH2)10COOH Lauric acid (laurel plant) 44.2
acid
n-Tetradecanoic Myristic acid (nutmeg
14:0 CH3(CH2)12COOH 53.9
acid genus)
n-Hexadecanoic
16:0 CH3(CH2)14COOH Palmitic acid (palm tree) 63.1
acid
n-Octadecanoic
18:0 CH3(CH2)16COOH Stearic acid (hard fat) 69.6
acid
Arachidic acid (legume
20:0 CH3(CH2)18COOH n-Eicosanoic acid 76.5
genus)
n-Tetracosanoic Lignoceruc acid (wood
24:0 CH3(CH2)22COOH 86.0
acid and wax)
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)
