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5.8: Glossary- The Chemical Level of Organization

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    acid: compound that releases hydrogen ions (H+) in solution

    activation energy: amount of energy greater than the energy contained in the reactants, which must be overcome for a reaction to proceed

    adenosine triphosphate (ATP): nucleotide containing ribose and an adenine base that is essential in energy transfer

    amino acid: building block of proteins; characterized by an amino and carboxyl functional groups and a variable side-chain

    anion: atom with a negative charge

    atom: smallest unit of an element that retains the unique properties of that element

    atomic number: number of protons in the nucleus of an atom

    base: compound that accepts hydrogen ions (H+) in solution

    bond: electrical force linking atoms

    buffer: solution containing a weak acid or a weak base that opposes wide fluctuations in the pH of body fluids

    carbohydrate: class of organic compounds built from sugars, molecules containing carbon, hydrogen, and oxygen in a 1-2-1 ratio

    catalyst: substance that increases the rate of a chemical reaction without itself being changed in the process

    cation: atom with a positive charge

    chemical energy: form of energy that is absorbed as chemical bonds form, stored as they are maintained, and released as they are broken

    colloid: liquid mixture in which the solute particles consist of clumps of molecules large enough to scatter light

    compound: substance composed of two or more different elements joined by chemical bonds

    concentration: number of particles within a given space

    covalent bond: chemical bond in which two atoms share electrons, thereby completing their valence shells

    decomposition reaction: type of catabolic reaction in which one or more bonds within a larger molecule are broken, resulting in the release of smaller molecules or atoms

    denaturation: change in the structure of a molecule through physical or chemical means

    deoxyribonucleic acid (DNA): deoxyribose-containing nucleotide that stores genetic information

    disaccharide: pair of carbohydrate monomers bonded by dehydration synthesis via a glycosidic bond

    disulfide bond: covalent bond formed within a polypeptide between sulfide groups of sulfur-containing amino acids, for example, cysteine

    electron shell: area of space a given distance from an atom’s nucleus in which electrons are grouped

    electron: subatomic particle having a negative charge and nearly no mass; found orbiting the atom’s nucleus

    element: substance that cannot be created or broken down by ordinary chemical means

    enzyme: protein or RNA that catalyzes chemical reactions

    exchange reaction: type of chemical reaction in which bonds are both formed and broken, resulting in the transfer of components

    functional group: group of atoms linked by strong covalent bonds that tends to behave as a distinct unit in chemical reactions with other atoms

    hydrogen bond: dipole-dipole bond in which a hydrogen atom covalently bonded to an electronegative atom is weakly attracted to a second electronegative atom

    inorganic compound: substance that does not contain both carbon and hydrogen

    ionic bond: attraction between an anion and a cation

    ion: atom with an overall positive or negative charge

    isotope: one of the variations of an element in which the number of neutrons differ from each other

    kinetic energy: energy that matter possesses because of its motion

    lipid: class of nonpolar organic compounds built from hydrocarbons and distinguished by the fact that they are not soluble in water

    macromolecule: large molecule formed by covalent bonding

    mass number: sum of the number of protons and neutrons in the nucleus of an atom

    matter: physical substance; that which occupies space and has mass

    molecule: two or more atoms covalently bonded together

    monosaccharide: monomer of carbohydrate; also known as a simple sugar

    neutron: heavy subatomic particle having no electrical charge and found in the atom’s nucleus

    nucleotide: class of organic compounds composed of one or more phosphate groups, a pentose sugar, and a base

    organic compound: substance that contains both carbon and hydrogen

    pH: negative logarithm of the hydrogen ion (H+) concentration of a solution

    peptide bond: covalent bond formed by dehydration synthesis between two amino acids

    periodic table of the elements: arrangement of the elements in a table according to their atomic number; elements having similar properties because of their electron arrangements compose columns in the table, while elements having the same number of valence shells compose rows in the table

    phospholipid: a lipid compound in which a phosphate group is combined with a diglyceride

    phosphorylation: addition of one or more phosphate groups to an organic compound

    polar molecule: molecule with regions that have opposite charges resulting from uneven numbers of electrons in the nuclei of the atoms participating in the covalent bond

    polysaccharide: compound consisting of more than two carbohydrate monomers bonded by dehydration synthesis via glycosidic bonds

    potential energy: stored energy matter possesses because of the positioning or structure of its components

    product: one or more substances produced by a chemical reaction

    prostaglandin: lipid compound derived from fatty acid chains and important in regulating several body processes

    protein: class of organic compounds that are composed of many amino acids linked together by peptide bonds

    proton: heavy subatomic particle having a positive charge and found in the atom’s nucleus

    purine: nitrogen-containing base with a double ring structure; adenine and guanine

    pyrimidine: nitrogen-containing base with a single ring structure; cytosine, thiamine, and uracil

    radioactive isotope: unstable, heavy isotope that gives off subatomic particles, or electromagnetic energy, as it decays; also called radioisotopes

    reactant: one or more substances that enter into the reaction

    ribonucleic acid (RNA): ribose-containing nucleotide that helps manifest the genetic code as protein

    solution: homogeneous liquid mixture in which a solute is dissolved into molecules within a solvent

    steroid: (also, sterol) lipid compound composed of four hydrocarbon rings bonded to a variety of other atoms and molecules

    substrate: reactant in an enzymatic reaction

    suspension: liquid mixture in which particles distributed in the liquid settle out over time

    synthesis reaction: type of anabolic reaction in which two or more atoms or molecules bond, resulting in the formation of a larger molecule

    triglyceride: lipid compound composed of a glycerol molecule bonded with three fatty acid chains

    valence shell: outermost electron shell of an atom

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