BCM 1.3: Structure, Function, & Properties of Lipids

Vocabulary practice flashcards covering lipid definitions, fatty acid nomenclature, simple/compound/derived lipid classifications, eicosanoids, and steroids based on Module 1.3 Biochemistry lecture notes.

Lipids

A large and diverse group of naturally occurring organic compounds related by their solubility in nonpolar organic solvents (such as ether, chloroform, acetone, and benzene) and general insolubility in water.

Fatty Acid

A long-chain aliphatic carboxylic acid that serves as a basic building block of lipids and is liberated upon lipid hydrolysis.

Amphipathic

Describing a molecule that contains both a hydrophobic nonpolar component (such as a hydrocarbon chain) and a hydrophilic polar component (such as a carboxyl group).

Essential Fatty Acids

Fatty acids that cannot be synthesized by the human body and must be acquired through dietary intake, specifically $\alpha\text{-linolenic acid}$ ($\omega\text{-3}$) and linoleic acid ($\omega\text{-6}$).

Saturated Fatty Acid

A fatty acid containing no carbon-carbon double bonds, possessing a uniform rod-like shape that allows tight molecular packing and results in a higher melting point.

Unsaturated Fatty Acid

A fatty acid containing one or more double bonds (typically in the cis configuration), which introduces a kink in its shape, preventing tight packing and lowering its melting point.

Cis Configuration

A structural isomerism in unsaturated fatty acids where acyl chain sections attached to the double bond lie on the same side, introducing a kink into the hydrocarbon chain.

Delta ($\Delta$) Numbering System

A fatty acid nomenclature system where numbering starts at the carboxyl carbon ($\text{C1}$), and superscript numbers on the $\Delta$ symbol denote the positions of double bonds relative to $\text{C1}$.

Omega ($\omega$) Numbering System

A fatty acid nomenclature system where double bond positions are designated relative to the terminal methyl carbon ($\omega$ carbon) located at the end opposite the carboxyl group.

Lauric Acid

A $12\text{-carbon}$ saturated fatty acid ($\text{C}_{12}\text{H}_{24}\text{O}_2$) with the IUPAC name n-dodecanoate.

Palmitic Acid

A $16\text{-carbon}$ saturated fatty acid ($\text{C16:0}$) with the IUPAC name n-hexadecanoate, which is one of the most abundant saturated fatty acids in living organisms.

Stearic Acid

An $18\text{-carbon}$ saturated fatty acid ($\text{C18:0}$) with the IUPAC name n-octodecanoate.

Oleic Acid

An $18\text{-carbon}$ monounsaturated fatty acid ($\text{C18:1}\Delta^9$, $\omega\text{-9}$) with the IUPAC name cis-9-octadecenoate, which represents the most abundant unsaturated fatty acid.

Linoleic Acid

An $18\text{-carbon}$ polyunsaturated essential fatty acid ($\text{C18:2}\Delta^{9,12}$, $\omega\text{-6}$) with the IUPAC name all cis-9,12-octadecadienoate.

Arachidonic Acid

A $20\text{-carbon}$ polyunsaturated fatty acid ($\text{C20:4}\Delta^{5,8,11,14}$, $\omega\text{-6}$) with the IUPAC name all cis 5,8,11,14-eicosatetraenoate, which serves as a precursor for prostaglandins, leukotrienes, and thromboxanes.

Triglyceride

A simple lipid composed of a triester of three fatty acid molecules bonded to a glycerol backbone; also termed a triacylglycerol (TAG).

Simple Triglyceride

A triglyceride in which all three attached fatty acid chains are chemically identical, such as tristearin.

Mixed Triglyceride

A triglyceride containing two or three different fatty acid residues attached to its glycerol backbone.

Saponification

The alkaline hydrolysis of triglyceride ester bonds using a strong alkali, breaking ester links to generate glycerol and salts of fatty acids (soap).

Waxes

Simple lipids consisting of esters of long-chain fatty acids ($\text{C}_{16}\text{--C}_{36}$) with high molecular weight monohydric alcohols ($\text{C}_{24}\text{--C}_{34}$) other than glycerol.

Compound Lipids

Lipids that yield fatty acids, an alcohol, and additional chemical structures (such as phosphoric acid, carbohydrates, or proteins) upon hydrolysis.

Phospholipids

Compound lipids consisting of phosphatidic acid (glycerol, fatty acids, and phosphoric acid) bound in an ester linkage to a nitrogenous base or polar organic head group.

Phosphatidylcholine

A major membrane phospholipid (commonly referred to as lecithin) composed of phosphatidic acid esterified to choline, playing key roles in fat transport and lipid emulsification.

Phosphatidylethanolamine

A prominent nervous tissue phospholipid (commonly referred to as cephalin) involved in neural function, blood coagulation, and mitochondrial membrane integrity.

Plasmalogen

A class of glycerophospholipid containing an alkenyl group via an ether linkage at the $\text{C1}$ position of glycerol, serving as an antioxidant and structural component in myelin sheaths.

Sphingomyelin

A sphingolipid abundant in nervous tissue, brain, and red blood cells, consisting of a sphingosine alcohol backbone attached to a fatty acid, phosphoric acid, and choline.

Glycolipids

Compound lipids consisting of a fatty acid, a sphingosine or glycerol backbone, and a carbohydrate residue, completely lacking a phosphate group.

Cerebroside

A glycolipid containing a single carbohydrate residue attached to a ceramide residue, found abundantly in myelin sheaths of nerves and brain tissue.

Proteolipids

Complexes of proteins and lipids that display the solubility characteristics of lipids, playing essential roles in cell membrane signaling and transport in nerve tissues.

Derived Lipids

A heterogeneous group of lipids produced through metabolic derivation or transformation of fatty acid carbon skeletons, including terpenes and steroids.

Terpenes

Derived lipids synthesized from repeating $5\text{-carbon}$ isoprene ($\text{C}_5\text{H}_8$) units according to the Isoprene Rule, resulting in carbon totals in multiples of five ($5n$).

Monoterpenes

A terpene subclassification containing $2$ isoprene units and $10$ carbon atoms ($\text{C}_{10}$).

Triterpenes

A terpene subclassification containing $6$ isoprene units and $30$ carbon atoms ($\text{C}_{30}$).

Perhydrocyclopentanophenanthrene

The tetracyclic fused ring system (composed of rings A, B, C, and D) that forms the core structural nucleus of all steroids.

Cholesterol

A $27\text{-carbon}$ sterol ($\text{C}_{27}$) containing a double bond at $\text{C5--C6}$ and a hydroxyl group at $\text{C3}$, providing cell membrane rigidity and serving as the primary precursor for bile acids, steroid hormones, and vitamin D.

Bile Acids

Steroid derivatives containing $24$ carbon atoms ($\text{C}_{24}$) with a $5\text{-carbon}$ side chain at $\text{C17}$ terminating in a carboxyl group, acting as emulsifying agents in lipid digestion.

Cortisol

A physiologically active $21\text{-carbon}$ glucocorticoid steroid hormone (17-hydroxycorticosterone) produced by the adrenal cortex under pituitary ACTH regulation.

Aldosterone

An adrenal corticosteroid hormone that regulates body water and electrolyte metabolism by promoting sodium retention and potassium secretion.

Prostanoic Acid

A $20\text{-carbon}$ monocarboxylic acid containing an internal cyclopentane ring, an $\alpha\text{-chain}$, and an $\omega\text{-chain}$, acting as the direct precursor to prostaglandins.

Prostaglandins

A family of $20\text{-carbon}$ eicosanoids derived from prostanoic acid that regulate local processes including smooth muscle contraction, blood pressure, inflammation, and blood clotting.

Leukotrienes

Eicosanoids synthesized from arachidonic acid via the lipoxygenase pathway that feature three conjugated double bonds and function as extremely potent smooth muscle vasoconstrictors.

5-HPETE

A hydroperoxyeicosatetraenoic acid intermediate formed via the $5\text{-lipoxygenase}$ reaction in leukocytes, basophils, and macrophages during leukotriene biosynthesis.

Thromboxane $\text{A}_2$

An eicosanoid mediator derived from $\text{PGH}_2$ that acts as a vasoconstrictor and promotes platelet activation and aggregation in hemostasis.

Pheromones

Low molecular weight, volatile lipid compounds utilized by insects, plants, ciliates, and vertebrates for intraspecies chemical communication.