Biomolecules and Organic Macromolecules

A set of vocabulary flashcards covering the fundamental concepts of biology, including bioelements, organic chemistry basics, and the four major classes of macromolecules (carbohydrates, lipids, proteins, and nucleic acids).

Fundamental Bioelements

The six elements ($C, H, N, O, P, S$) that constitute approximately $98\%$ of the mass of every living organism, including bacteria, cabbages, and humans.

Essential Bioelements

Elements found in the form of oxides, mineral salts, or electrolytes, including $Na, Mg, Cl, K, \text{ and } Ca$.

Trace Elements

Elements present in concentrations less than $0.001\%$ atom but necessary for fundamental biochemical reactions, such as $Fe, Mn, Cu, B, V, Zn, Mo, \text{ and } Si$.

Isomers

Organic molecules that have the same molecular formula (identical type and number of atoms) but differ in their chemical and physical properties and react differently in chemical reactions.

Functional Group

A part of a molecule's structure characterized by specific elements and a well-defined structure that confers a typical reactivity to the compound; it is the center of chemical reactivity.

Polymer

A complex molecule formed by repeated units of simple substances called monomers.

Condensation Reaction

The chemical process used for the synthesis of a polymer in which a molecule of water ($H_2O$) is released.

Hydrolysis

The breakdown of a polymer into individual monomers through the addition of water ($H_2O$).

Monosaccharides

The monomeric units of carbohydrates, which are ternary compounds of $H, O, \text{ and } C$ containing between $3$ and $7$ carbon atoms.

Trioses

Monosaccharides with $3$ carbon atoms, such as glyceraldehyde (an aldose) and dihydroxyacetone (a ketose), both having the formula $C_3H_6O_3$.

Pentoses

Monosaccharides with $5$ carbon atoms, including ribose (a constituent of RNA) and deoxyribose (a constituent of DNA).

Hexoses

Monosaccharides with $6$ carbon atoms, with prominent examples being fructose, galactose, and glucose.

Disaccharides

Carbohydrates formed by two monosaccharides linked by a covalent glycosidic bond, such as sucrose ($\alpha$-glucose + fructose), lactose ($\beta$-glucose + galactose), and maltose ($2 \times \alpha$-glucose).

Starch

A reserve homopolysaccharide in plants made of $\alpha$-glucose units, consisting of linear amylose ($20\%$) and branched amylopectin ($80\%$) linked by $\alpha, 1-4$ and $\alpha, 1-6$ bonds.

Glycogen

A highly branched reserve homopolysaccharide of $\alpha$-glucose in animal cells, stored in liver and muscle tissues.

Cellulose

A structural polysaccharide in plants characterized by $\beta, 1-4$ glycosidic bonds between glucose molecules; it is indigestible by humans and acts as dietary fiber.

Chitin

A complex structural carbohydrate composed of long chains of glucosamine that forms the exoskeleton of insects and other invertebrates.

Triglycerides

Energy storage lipids composed of one glycerol molecule (a trivalent alcohol) linked by ester bonds to three molecules of fatty acids.

Saturated Fatty Acids

Long hydrocarbon chains containing the maximum possible number of hydrogen atoms and no carbon-carbon double bonds, usually solid at room temperature.

Unsaturated Fatty Acids

Hydrocarbon chains containing one or more double bonds ($C=C$), which influences their melting point and typically makes them liquid (oils) at room temperature.

Phospholipids

Amphipathic molecules consisting of glycerol, two fatty acids, and a polar phosphate group, serving as the primary structural components of cell membranes.

Cholesterol

A lipid essential for cell membrane structure and flexibility; it is the precursor for all steroid hormones and is primarily produced by the liver ($80\%$).

Carotenoids

Photosensitive molecules such as $\beta$-carotene, which can be split into two molecules of Vitamin A (retinol), a precursor to rhodopsina used for light capture in the eyes.

Amino Acids

The monomers of proteins, each containing a central $\alpha$-carbon, an amino group ($-NH_2$), a carboxyl group ($-COOH$), and a unique side chain ($R$).

Zwitterion

The dipolar ionic state in which an amino acid exists because it contains both an acidic carboxyl group and a basic amino group.

Primary Structure

The first level of protein organization, defined by the specific linear sequence of amino acid residues in the polypeptide chain.

Secondary Structure

Protein organization determined by hydrogen bonds between the carbonyl oxygen and amide hydrogen of the peptide backbone, forming $\alpha$-helices or $\beta$-sheets.

Tertiary Structure

The overall three-dimensional shape of a protein resulting from interactions between distant amino acids, including disulfide bridges, ionic bonds, and van der Waals forces.

Quaternary Structure

The highest level of protein organization, occurring in multimeric proteins composed of two or more polypeptide chains (subunits).

Protein Denaturation

The loss of a protein's native conformation and biological activity caused by the breaking of weak stabilizing interactions due to heat, extreme pH, or organic solvents.

Hemoglobin

A globular protein found in red blood cells that transports oxygen ($O_2$) using four heme groups, each containing an iron ($Fe$) atom.

Collagen

A fibrous, water-insoluble protein that provides structural support in tendons and bones, representing $25\%$ of all organism proteins.

Prions

Proteins that can adopt an incorrect conformation and induce normal proteins of the same type to misfold, leading to fatal neurological degenerations like spongiform encephalopathy.

Anabolism

The set of synthetic metabolic reactions that assemble simple substances into complex molecules, consuming energy (endoergonic).

Catabolism

The set of degradative metabolic reactions that break down complex organic compounds into simpler ones, releasing energy (esoergonic).

Caloric Value of Lipids

The energy released by the metabolism of fats, which is approximately $9.3\,kcal\,g^{-1}$.

Nucleotide

The monomer of nucleic acids, consisting of a phosphate group, a pentose sugar (ribose or deoxyribose), and a nitrogenous base.

Phosphodiester Bond

The covalent bond that links nucleotides in a strand, occurring between the $C3'$ hydroxyl group ($-OH$) and the $C5'$ phosphate group.

ATP (Adenosine Triphosphate)

The main energy source for cellular activities, composed of adenine, ribose, and three phosphate groups linked by two high-energy phosphoanhydride bonds.

NAD+ (Nicotinamide Adenine Dinucleotide)

A coenzyme composed of two nucleotides (one containing adenine and the other nicotinamide) that functions as an electron carrier in metabolic reactions.

Coenzyme A (CoA)

A fundamental metabolic coenzyme that functions as a carrier of acyl radicals, essential for the catabolism of fatty acids and cellular respiration.