Lipids

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Lipid Noun

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[lip-id]

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Lipid

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A large, nonpolar biological molecule that stores energy and is a major structural component of cell membranes.

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Example: This image shows how lipids called phospholipids form a lipid bilayer, with water-loving (hydrophilic) heads facing out and water-fearing (hydrophobic) tails facing in.

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Nonpolar Molecule Noun

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[non-poh-ler mol-uh-kyool]

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Nonpolar Molecule

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A molecule with no separation of charge, resulting in no positive or negative poles and general insolubility in water.

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Example: Two identical atoms share electrons equally, creating a nonpolar molecule with no positive or negative ends, which is why lipids don't mix with water.

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Fatty Acid Noun

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[fat-ee as-id]

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Fatty Acid

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A long-chain carboxylic acid that serves as a fundamental building block for many types of lipids, including triglycerides.

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Example: A fatty acid molecule consists of a long chain of carbon and hydrogen atoms (hydrocarbon chain) and a carboxyl group at one end.

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Saturated Fatty Acid Noun

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[sach-uh-rey-tid fat-ee as-id]

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Saturated Fatty Acid

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A type of fatty acid that contains no carbon-carbon double bonds in its long hydrocarbon chain.

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Example: This diagram shows a saturated fatty acid molecule, where the long carbon chain has only single bonds, allowing it to be fully 'saturated' with hydrogen atoms.

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Unsaturated Fatty Acid Noun

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[un-sach-uh-rey-tid fat-ee as-id]

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Unsaturated Fatty Acid

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A type of fatty acid containing one or more carbon-carbon double bonds, which causes a bend in its structure.

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Example: This diagram shows an unsaturated fatty acid has at least one double bond between carbon atoms, which creates a bend or 'kink' in its structure.

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cis geometric isomer Noun

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[sis jee-oh-met-rik ahy-suh-mer]

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cis geometric isomer

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An isomer where identical groups are oriented on the same side of a double bond, causing a kink in the molecule.

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Example: A cis isomer, like this fatty acid, has a 'kink' or bend in its molecular chain because of the arrangement of atoms around a double bond.

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Hydrogenation Noun

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[hahy-droj-uh-ney-shuhn]

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Hydrogenation

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An addition reaction where hydrogen gas reacts with carbon-carbon multiple bonds, converting an unsaturated compound to a saturated one.

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Example: This diagram shows a hydrogen molecule (H₂) being added to an unsaturated molecule (Alkene), breaking its double bond to form a saturated molecule (Alkane).

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Triglyceride Noun

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[trahy-glis-uh-rahyd]

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Triglyceride

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A lipid formed when three fatty acid molecules are bonded to a glycerol backbone, serving as the main form of stored fat.

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Example: This diagram shows a triglyceride is a type of lipid made of one glycerol molecule (blue) chemically bonded to three fatty acid chains (pink).

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Glycerol Noun

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[glis-er-ol]

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Glycerol

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A three-carbon alcohol molecule with three hydroxyl groups that functions as the backbone for triglycerides and phospholipids.

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Example: This image shows the glycerol molecule using a 2D diagram and a 3D model, with a key identifying its carbon, hydrogen, and oxygen atoms.

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Ester Bond Noun

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[es-ter bond]

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Ester Bond

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A covalent bond formed between a hydroxyl group and a carboxyl group, linking fatty acids to glycerol in triglycerides.

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Example: This diagram shows how a glycerol molecule and three fatty acids join via a condensation reaction, forming the ester bonds that create a triglyceride lipid.