Lipids - Nomenclature and Classification Practice Flashcards

A collection of vocabulary-style flashcards covering the nomenclature, chemical structure, classification, and functional properties of lipids as described in the lecture notes.

Lipids

A diverse group of compounds generally soluble in organic solvents but insoluble in water, serving as primary structural components and providing $9\,kcal/g$.

Acylglycerol

The scientific name for glycerol esters of fatty acids, also commonly referred to as glycerides.

Fats vs. Oils

Lipids distinguished by physical appearance at room temperature, where fats are solid and oils are liquid.

Shorthand Fatty Acid Notation (e.g., $18:1$)

A convention where the first number indicates the number of carbon atoms and the second indicates the number of double bonds.

$n$ (Omega) Designation

A numbering system for polyunsaturated fatty acids that counts carbon atoms starting from the methyl end of the chain.

Triacylglycerol (TAG)

A lipid containing three fatty acids esterified to a glycerol backbone, often abbreviated by the component fatty acids (e.g., $SSS$ for tristearin).

Saturated Fatty Acids

Fatty acids with no double bonds that act as an alkane with a $-COOH$ group; they are less reactive than unsaturated lipids.

Monounsaturated Fatty Acids

Fatty acids characterized by the presence of exactly one double bond.

Polyunsaturated Fatty Acids

Fatty acids containing two or more double bonds along the hydrocarbon chain.

Cis Configuration

The most common naturally occurring geometric configuration where $R$ groups are on the same side of the double bond.

Trans Configuration

A geometric configuration where $R$ groups are across the double bond, often resulting in a higher melting point than the cis form.

Hydrogenation

A chemical process that converts cis-double bonds into trans-configurations, which are more thermodynamically favourable but associated with health concerns.

Conjugated Double Bonds

A system where only one single bond exists between two double bonds (e.g., $-CH=CH-CH=CH-$).

Unconjugated Double Bonds

A system where a methylene ($CH_2$) group separates the double bonds (e.g., $-CH=CH-CH_2-CH=CH-$).

Ruminant Milk Fats

Fats from animals like cows or goats that contain unique short-chain fatty acids ($4-12C$) associated with the rancid odour of spoiled dairy.

Marine Oils

Oils from fish or cold-water mammals containing long-chain fatty acids with up to $6$ double bonds, making them highly prone to oxidation.

Lauric Acid ($12:0$)

A specific saturate found in high concentrations in palm oils (coconut, babassu) that allows them to remain liquid at room temperature due to short chain length.

Reversion

A flavour change in oils high in linolenic acid ($18:3n3$) where they develop grassy, hay-like, or fishy notes.

Simple Lipids

Lipids such as acylglycerides that consist of fatty acids connected to an alcohol like glycerol.

Enantiomers

Pairs of non-superimposable mirror-image molecules formed when a fatty acid is attached to glycerol, creating a chiral centre at $C2$.

Stereospecific Numbering ($sn$) System

A standard system used to label fatty acid positions ($sn-1$, $sn-2$, $sn-3$) based on a Fischer projection of glycerol with the $-OH$ on the left.

Plant Triacylglycerol Distribution

A pattern where unsaturated fatty acids (like linoleic acid) are typically located at the $sn-2$ position, with saturated fatty acids at $sn-1$ and $sn-3$ ($SUS$).

Compound Lipids

Lipids where a simple lipid is conjugated to a non-lipid molecule, such as carbohydrates (glycolipids) or proteins (lipoproteins).

Phospholipids

Lipids containing phosphoric acid attached to glycerol; they are major components of membranes and possess amphiphilic properties.

Amphiphilic

A molecule containing both lipophilic (fatty acid) and hydrophilic (phosphoric acid) portions, allowing it to be surface active.

Lecithins (Phosphatidylcholines)

A group of phospholipids used in food as emulsifiers to prevent chocolate bloom and inhibit ice crystal formation.

Saponification

The process of boiling fat with an alkali ($NaOH$) to separate the soap-forming (saponifiable) and non-soap-forming (unsaponifiable) fractions.

Unsaponifiable Fraction

The part of fat that does not form soaps, containing sterols, terpenic alcohols, squalene, and hydrocarbons; used to identify lipid origin.

Cholesterol

A sterol found exclusively in fats of animal origin.

Phytosterols

Bioactive sterols found in the unsaponifiable fraction of plant-based fats and oils.

Shortening

A functional property of fats where they retard the formation of a gluten network in products like cakes and shortbread.