Lipids - part 1

Vocabulary flashcards covering definitions, classifications, notation systems, and physical-property trends for lipids and fatty acids discussed in the lecture notes.

An organic compound insoluble (or only sparingly soluble) in water but soluble in non-polar solvents; includes fats, phospholipids, steroids, etc.

Lipid

Energy-storage lipid that stores chemical energy and provides thermal insulation and shock protection for organs.

Fat (Triacylglycerol)

Amphipathic membrane lipid containing glycerol (or sphingosine), two fatty acids, and a phosphate group; major component of cell membranes.

Phospholipid

Membrane lipid containing a carbohydrate moiety attached to a sphingosine backbone; involved in cell recognition.

Glycolipid

Steroid lipid that stabilizes cell membranes and serves as precursor to bile acids, steroid hormones, and vitamin D.

Cholesterol

Cholesterol-derived messenger lipid that regulates physiology (e.g., progesterone, testosterone, cortisol).

Steroid Hormone

Emulsification lipid derived from cholesterol that aids intestinal fat digestion and absorption.

Bile Acid

20-carbon oxygenated PUFA derivative (e.g., prostaglandins) acting as local chemical messenger.

Eicosanoid

Protective-coating lipid formed from a long-chain fatty acid and a long-chain alcohol; water-repellent.

Biological Wax

Lipid class (mainly triacylglycerols) that stores metabolic energy and carbon atoms.

Energy-Storage Lipid

Lipid class forming biological membranes; includes phospholipids, sphingoglycolipids, and cholesterol.

Membrane Lipid

Lipids (primarily bile acids) that disperse dietary fats into micelles for digestion.

Emulsification Lipid

Lipids (steroid hormones, eicosanoids) that transmit information between or within cells.

Messenger Lipid

Lipids (biological waxes) that form water-proof layers on plant leaves, feathers, skin, etc.

Protective-Coating Lipid

Base-catalyzed hydrolysis of an ester lipid that yields glycerol/alcohol and the salt of a fatty acid (soap).

Saponification

Lipid that undergoes hydrolysis in base to give smaller molecules; e.g., triacylglycerols, phospholipids, waxes.

Saponifiable Lipid

Lipid that does not hydrolyze in base; e.g., cholesterol, steroid hormones, bile acids, eicosanoids.

Nonsaponifiable Lipid

Naturally occurring, unbranched monocarboxylic acid (usually even-numbered C4–C26) forming lipid building blocks.

Fatty Acid

Fatty acid containing only carbon–carbon single bonds in its hydrocarbon chain.

Saturated Fatty Acid (SFA)

Fatty acid with one carbon–carbon double bond, typically in the cis-9 position (\Delta9).

Monounsaturated Fatty Acid (MUFA)

Fatty acid with two or more cis double bonds (up to six) in the carbon chain.

Polyunsaturated Fatty Acid (PUFA)

Fatty acid containing 12–26 carbon atoms.

Long-Chain Fatty Acid

Fatty acid containing 8–10 carbon atoms.

Medium-Chain Fatty Acid

Fatty acid containing 4–6 carbon atoms.

Short-Chain Fatty Acid

System that lists total carbons:double bonds, followed by superscript positions of double bonds counted from the carboxyl carbon (C-1).

Delta (\Delta) Notation

System that identifies the position of the terminal (endmost) double bond counted from the methyl (\omega) end of the fatty acid.

Omega (\omega) Notation

Unsaturated fatty acid whose last double bond is three carbons from the methyl end (e.g., \alpha-linolenic acid, EPA, DHA).

Omega-3 Fatty Acid

Unsaturated fatty acid whose last double bond is six carbons from the methyl end (e.g., linoleic acid, arachidonic acid).

Omega-6 Fatty Acid

Fatty acid solubility decreases as carbon chain length increases; limited solubility due to polar carboxyl group vs. non-polar tail.

Water-Solubility Trend

Fatty acid melting point rises with longer chains and falls with more cis double bonds; SFAs > MUFAs > PUFAs of same length.

Melting-Point Trend

Cis bonds introduce ~30° bends, hinder close packing, reduce intermolecular forces, and lower melting points.

Cis Double-Bond Effect

Common 16-carbon saturated fatty acid found in fats and oils.

Palmitic Acid (16:0)

Major monounsaturated fatty acid in olive oil; has one cis-9 double bond.

Oleic Acid (18:1 \Delta9, \omega-9)

Essential omega-6 PUFA with two cis double bonds; precursor to arachidonic acid.

Linoleic Acid (18:2 \Delta9,12, \omega-6)

Omega-6 PUFA serving as precursor for eicosanoids such as prostaglandins and leukotrienes.

Arachidonic Acid (20:4 \Delta5,8,11,14, \omega-6)

20:5 \Delta5,8,11,14,17 omega-3 PUFA abundant in fish oils; anti-inflammatory effects.

EPA (Eicosapentaenoic Acid)

22:6 \Delta4,7,10,13,16,19 omega-3 PUFA critical for brain and retinal development.

DHA (Docosahexaenoic Acid)

Characteristic of naturally occurring fatty acids; carbon skeleton lacks side chains.

Unbranched Carbon Chain

Biosynthetic pattern resulting in fatty acids with even numbers (C4, C6, …, C24) of carbon atoms.

Even-Numbered Carbons

Role of stored fats surrounding organs, cushioning them against physical impact.

Mechanical Shock Protection