Lipids - Structure, Properties, and Functions Flashcards

A complete set of vocabulary flashcards covering the chemical composition, classification, properties, digestion, and functions of lipids based on lecture notes.

Fats

Lipids that are solid at room temperature.

Oils

Lipids that are liquid at room temperature.

Elemental Composition of Lipids

Composed of Carbon ($C$), Hydrogen ($H$), and Oxygen ($O$) in different proportions compared to carbohydrates.

Triglyceride

The chemical name given to a fat, formed when one glycerol molecule joins with three fatty acids, eliminating three water molecules ($H_2O$) in a condensation reaction.

Glycerol

A trihydric alcohol containing three hydroxyl ($OH$) groups.

Fatty Acid Molecule

An organic compound represented by the formula $CH_3(CH_2)_nCOOH$, consisting of a long hydrocarbon chain with a carboxyl group ($COOH$) at one end and a methyl group ($CH_3$) at the other.

Triglyceride Formation

A condensation reaction where each hydroxyl ($OH$) group of a glycerol molecule combines with hydrogen ($H$) atoms from three fatty acids, resulting in the loss of three water molecules ($H_2O$).

Saturation

Refers to the amount of hydrogen molecules present in a fatty acid.

Saturated Fatty Acid

A fatty acid in which each carbon atom is fully saturated with hydrogen atoms and no double bonds occur between carbon atoms; solid at room temperature ($18^\text{o}\text{C}$) with a high melting point.

Monounsaturated Fatty Acid

A fatty acid in which each carbon atom is not fully saturated with hydrogen atoms and contains one double bond between carbon atoms; soft or liquid at room temperature ($18^\text{o}\text{C}$) with a low melting point.

Polyunsaturated Fatty Acid (PUFA)

A fatty acid in which carbon atoms are not fully saturated with hydrogen atoms and contain more than one double bond between carbon atoms; soft or liquid at room temperature ($18^\text{o}\text{C}$) with the lowest melting point of all fatty acids.

Essential Fatty Acids (EFAs)

Fatty acids that cannot be manufactured by the body and must be obtained from food, specifically linoleic acid (omega-6) and alpha-linolenic acid (omega-3).

Omega-3 Fatty Acid

An unsaturated fatty acid where a carbon-carbon double bond occurs between the 3rd and 4th carbon atoms on the hydrocarbon chain from the methyl end.

Cis Fatty Acids

Fatty acids in which the hydrogen atoms on either side of the double bond are both above or both below the carbon chain.

Trans Fatty Acids

Fatty acids in which the hydrogen atoms on either side of the double bond are on opposite sides of the carbon chain.

Melting (slip) Point

The temperature range ($30\text{--}40^\text{o}\text{C}$) at which solid fats melt when heated.

Smoke Point

The temperature at which heated lipids begin to decompose ($200^\text{o}\text{C}$ for fats, $250^\text{o}\text{C}$ for oils), causing glycerol to separate and break down into acrolein, producing a blue smoke and acrid smell.

Flash Point

The temperature of extreme overheating ($310^\text{o}\text{C}$ for fats, $325^\text{o}\text{C}$ for oils) where lipids emit a vapour that can spontaneously ignite.

Emulsion

A colloidal solution formed when two immiscible liquids are forced to mix together.

Colloidal Solution

A solution with suspended microscopic insoluble particles distributed evenly throughout another substance.

Water in Oil Emulsion

An emulsion where tiny droplets of water are dispersed throughout oil or fat, such as in butter and margarine.

Oil in Water Emulsion

An emulsion where tiny droplets of oil are dispersed throughout water, such as in milk and mayonnaise.

Temporary Emulsion

An emulsion formed by shaking two immiscible liquids vigorously together without an emulsifier, which separates if left to stand.

Permanent Emulsion

An emulsion formed when an emulsifier is added to two immiscible liquids, preventing them from separating.

Emulsifier

A molecule with a hydrophilic (water-loving) head that attaches to water and a hydrophobic (water-hating) tail that attaches to oil, holding two immiscible liquids together.

Stabilisers

Long-chained molecules that help to maintain emulsions by separating oil droplets and preventing them from coalescing.

Hydrogenation

A process whereby hydrogen gas, in the presence of a nickel catalyst, is forced through the double bond of an unsaturated oil, converting it into a saturated solid fat.

Rancidity

The spoilage or decomposition of lipids resulting in an unpleasant odour and taste.

Oxidative Rancidity

Lipid spoilage occurring when oxygen in the air combines with carbon atoms at the double bond of an unsaturated fatty acid.

Hydrolytic Rancidity

Lipid spoilage occurring when enzymes (lipases) or bacteria break down lipids into glycerol and fatty acids.

Plasticity

A property describing how soft, pliable, and malleable a fat is at a given temperature, determined by its degree of saturation.

Viscosity

A property describing a substance that is thick, sticky, and semi-fluid in consistency.

Lipase

An enzyme present in pancreatic juice and intestinal juice that hydrolyses lipids into fatty acids and glycerol.

Lacteals

Lymphatic vessels inside the villi of the small intestine through which digested fatty acids and glycerol pass to enter the lymphatic system.

Adipose Tissue

Tissue under the skin where excess digested lipids are stored to insulate the body and act as an energy reserve.