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Fats are a class of lipids—triglycerides composed of a glycerol backbone esterified to three fatty acid chains. They are soluble in organic solvents and insoluble in water, which allows them to store energy, insulate, and form cell membranes.
Each triglyceride contains a hydrophilic glycerol head and three hydrophobic fatty‑acid tails made of hydrocarbon chains. The non‑polar C–C and C–H bonds render the tails water‑resistant, while the glycerol’s hydroxyl groups give the head a polar, water‑friendly character. This amphipathic nature underpins many biological functions.
Hydrocarbon tails drive the spontaneous assembly of micelles in aqueous environments. When the concentration of fat molecules exceeds the critical micelle concentration (CMC), the hydrophobic tails cluster inward, leaving the polar heads exposed to water. This structure is essential for processes such as digestion and detergent action.
“Saturation” describes the number of double bonds in a fatty‑acid chain. Saturated fats have no double bonds, yielding straight, tightly packed tails that remain solid at room temperature. Unsaturated fats contain one or more double bonds, introducing kinks that prevent close packing and result in liquids or semi‑solids (oils) at the same temperature. Consequently, saturated fats possess higher melting points and are more resistant to oxidation.
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