Topic 4: Lipids

Vocabulary-style flashcards covering the introduction, properties, biological functions, and specific types of lipids including fatty acids, glycerol, phospholipids, waxes, and steroids.

Lipids

Organic compounds made of carbon, hydrogen, and oxygen that are nonpolar molecules, soluble only in nonpolar solvents and insoluble in water.

Adipose tissue

The connective tissue in the body where oily or greasy nonpolar lipid molecules are stored as a reservoir of energy.

Ester bond

A covalent bond formed between a molecule of glycerol and a fatty acid through a condensation reaction involving the elimination of water.

Fatty acids

Carboxylic acids with the general formula $CH_3(CH_2)_nCOOH$, consisting of a long hydrocarbon chain and a carboxyl group.

Saturated fatty acids

Fatty acids like stearic acid where the hydrocarbon chain contains the maximum number of hydrogen atoms and all carbon atoms have single bonds.

Unsaturated fatty acids

Fatty acids like oleic acid that contain one or more double bonds between carbon atoms, resulting in fewer hydrogen atoms and a bend in the molecule.

Monounsaturated

A fatty acid that contains exactly one double bond in its hydrocarbon chain.

Polyunsaturated

A fatty acid that contains two or more double bonds in its hydrocarbon chain.

Glycerol

A trihydric alcohol with the formula $C_3H_8O_3$ and IUPAC name $1, 2, 3$-Propanetriol, used in the production of dynamite, cosmetics, and pharmaceuticals.

Triglycerides

The most common lipids in cells, formed by esterifying one glycerol molecule with three fatty acid molecules.

Lipase

The enzyme required to hydrolyse fats into their constituent units of glycerol and fatty acids.

Phospholipids

Amphipathic molecules containing a phosphate group ($PO_4^{3-}$) instead of one fatty acid chain, serving as major constituents of cell membranes.

Amphipathic molecule

A molecule that contains both polar (hydrophilic) and nonpolar (hydrophobic) regions.

Glycolipids

Lipids containing a sugar residue (monosaccharide, oligosaccharide, or polysaccharide) that are widely distributed in the brain and nerve cells.

Waxes

Esters formed from long-chain alcohols and long-chain carboxylic acids, often serving as water repellents or protective coatings.

Beeswax

An animal wax produced by worker bees ($Apis mellifera$) with the approximate chemical formula $C_{15}H_{31}COOC_{30}H_{61}$.

Carnauba wax

Also known as Brazil wax or palm wax, it is the hardest wax with a high melting point ($78$-$85^{\circ}\text{C}$) obtained from the leaves of $Copernicia prunifera$.

Steroids

Hydrophobic lipid molecules, such as testosterone and estrogen, characterized by a set of four ring structures.

Cholesterol

A structural component of cell membranes with the formula $C_{27}H_{45}OH$ that serves as the precursor for all steroid hormones.

Lipoproteins

Entities like LDL and HDL that transport hydrophobic substances like cholesterol and fats through the blood.

Metabolic Energy Output (Lipids)

Lipids yield approximately $38.9\,kJ\,g^{-1}$ of energy, which is more than double the energy yield of carbohydrates.