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atoms with different numbers of neutrons in their nuclei

ionic bond

an attraction between ions of opposite charge that holds them together to form a stable molecule

covalent bond

a chemical bond formed by two atoms sharing one or more pairs of electrons

hydrogen bond

bond in which a hydrogen atoms is covalently bonded to one oxygen or nitrogen atom is attracted to another oxygen or nitrogen atom

chemical reactions

involve making or breaking bonds between atoms

endergonic reaction

reactions that absorb more energy than they release


reaction that releases more energy than it absorbs

synthesis reaction

when two or more atoms, ions, or molecules combine to form new and larger molecules


synthesis reactions in living organisms

decomposition reaction

reaction when bonds are broken


decomposition reactions in living organisms

inorganic compounds

small and simple, lack carbon, ionic bonds (oxygen, carbon dioxide, salts, acids and bases)

organic compounds

contain carbon and hydrogen, complex, covalent bonds, macromolecules


polar molecule; capable of forming four hydrogen bonds with nearby water molecules; excellent solvent; reactant or product in many chemical reactions, splitting and rejoining or hydrogen and hydroxide ions; excellent temperature buffer


a substance that dissociates into one or more hydrogen ions and one or more negative ions (anions), hydrogen donor


dissociates into one or more positive ions (cations) plus one or more negatively charged hydroxide ions


a substance that dissociates in water into cations and anions

functional groups

specific groups of atoms that are most commonly involved in chemical reactions and are responsible for most of the characteristic chemical properties and many of the physical properties of a particular organic compound

hydroxyl group

alcohols, hydrophilic, --OH

amino group

function as bases because they readily accept hydrogen ions

sulfhydryl group

helps stabilize the intricate structure of many proteins

carboxyl group

a source of hydrogen ions, molecules containing it have acidic properties


can be used to stand for the remainder of the molecule

dehydration synthesis or condensation reaction

hydrogen atom and hydroxyl group combine to produce water


sugars and starches; functions: building block of DNA, cell walls, synthesis of amino acids and fats in cell membranes, food reserves, to fuel cell activities with a ready source of energy; made of CHO


two molecules with the same chemical formula but different structures and properties


water is added and comlex molecules break down


tens or hundreds of monosaccharides joined through dehydration synthesis; include: glycogen, cellulose, dextran, chitin, starch; broken down by amylase


nonpolar; insoluble in water; function in energy storage and provide the structure of membranes and some cell walls

simple lipids

fats or triglycerides; contain an glycerol and fatty acids; primary function is formation of plasma membranes that enclose cells

ester linkage

bond formed when glycerol attaches to fatty acid and water is removed


fatty acid that has no double bonds


fatty acids that hae double bonds; create kinks in the chian, which keep the chains apart from one another

complex lipids

contain elements such as phosphorus, nitrogen, and sulfer in addition to CHO


made up of glycerol, two fatty acids, and a phosphate group bonded to one of several organic groups; have polar heads and nonpolar tails; mycobacterium cell walls rich in complex lipids


four interconnected carbon rings; with and --OH group is called a sterol; sterols separate fatth acid chains


organic molecules that contain CHON, some also contain sulfur; 50% of cell's dry weight; functions: enzymes, transporter, bacteriocins, toxins, contraction and movement, structures, hormones, and antibodies

amino acids

building blocks of proteins; contain carboxyl group and one amino group;


configurations of amino acids; designated by D and L; most are L; glucose occurs as D-glucose

peptide bonds

bonds between amino acids; dehydration synthesis

levels of protein structure

primary, secondary, tertiary and quaternary


proteins unravel and lose characteristic shape and function

conjugated proteins

combinations of amino acids with other organic or inorganic components

deoxyribonucleic acid

the substance of which genes are made; made of sugar and phosphate backbone (double helix) and nitrogenous bases; A and G are purines, C and T/U are pyrimidines; G+C = 3 H bonds; A + T = 2 H bonds

ribonucleic acid

single helix; same as DNA except uracil instead of thymine; mRNA, rRNAand tRNA


adenine, cytosine, guanine, thymine and uracil

adenosine triphosphate

the principal energy carrying molecule of all cells and indespensable to the life of the cell; can be stored in every cell, where its potential energy is not released until needed; and adenosine unit (adenine and ribose) and three phosphate groups

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