Lipids
Lipids are organic molecules characterized by low solubility in water and are relatively
hydrophobic.
There are different biological roles of lipids, including storage lipids, membrane lipids, and
signaling lipids.
Storage lipids include fatty acids, triacylglycerols, and waxes.
Fatty acids are carboxylic acids with hydrocarbon chains that can be saturated or
unsaturated.
Nomenclature of fatty acids is based on the number and position of double bonds.
Essential fatty acids are necessary for human health but cannot be synthesized by the
body.
Physical properties of lipids, such as solubility in water and melting points, are affected by
the length and saturation of hydrocarbon chains.
Triacylglycerols consist of three fatty acids esterified to a glycerol molecule.
Triacylglycerols are stored energy forms and can form oil droplets in cells.
Different dietary sources of fat contain different combinations of fatty acids, with plant
fats being more unsaturated and animal fats being more saturated.
Hydrogenation is a food processing technique used to solidify oils, improve shelf life, and
increase melting points, but can result in the formation of trans fatty acids, which are
associated with health risks.
Formation of (Unhealthy) Trans Fatty Acids
Polyunsaturated fatty acids (PUFAs) ω-6 and ω-3 fatty acids.
Optimal dietary ratio for PUFAs: 1:1 to 4:1.
Typical North American diet?
Mediterranean diet?
Essential fatty acid: α-linolenic acid [18:3(Δ9,12,15)].
ω-6 fatty acids: precursor of pro-inflammatory cytokines.
ω-3 fatty acids: precursor of anti-inflammatory cytokines.
Dietary sources of PUFAs ω-6 fatty acids: Seeds, nuts, and their oils.
Dietary sources of PUFAs ω-6 fatty acids: Soybean oil (used in processed foods, fast
food).