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35 terms

Biology Holt McDougal Chapter 2

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atom
smallest basic unit of matter
compound
substance made of atoms of different elements that are bonded together in a set ratio
covalent bond
chemical bond formed when two atoms share one or more pairs of electrons
element
substance made of only one type of atom that cannot be broken down by chemical means
ion
atom that has gained or lost one or more electron
ionic bond
chemical bond formed between oppositely charged ions
molecule
two or more atoms held together by covalent bonds, not necessarily a compound
hydrogen bond
attraction between a slightly positive hydrogen atom and a slightly negative atom
cohesion
attration between molecules of the same substance
adhesion
attractions between molecules of different substances
solution
mixture that is consistant throughout: also called a homogeneous mixture
solute
substance that dissolves in a solvent and is present at a lower concentration than the solvent
solvent
substance in which solutes dissolve and that is present in greatest concentration in a solution
acid
substance that gives up a proton (H+) when dissolved in a solution
base
compound that takes up a proton (H+) when dissolved in a solution
pH
measurement of acidity; related to the concentration of free hydrogen in a solution
monomer
molecular subunit of a polymer
polymer
large, carbon-based molecule formed by the smaller sub-units called monomers
carbohydrate
molecule made of carbon of carbon, hydrogen, and oxygen; includes sugers and starches
fatty acid
hydrocarbon chain often bonded to glycerol in a lipid
protein
polymer made up of amino acids linked by peptide bonds; folds into a particular structure depending on bonds between amino acids
lipid
nonpolar molecule made up of carbon, hydrogen, and oxygen; includes fats and oils
nucleic acid
polymer of nucleotides; the genetic material of organisms
chemical reaction
process by which substances turn into different substances through the making and breaking of chemical bonds
reactant
substance that is changed by a chemical reation
product
substance formed by a chemical reation
bond energy
amount of energy needed to break a bond between two particular atons; or the amount of energy released when a bond forms between two particular atoms
equilibrium
condition in which reactants and products of a chemical reaction are formed at the same rate
activation energy
the lowest amount of energy needed to start a chemical reaction
exothermic
chemical reaction that yields a net release of energy in the form of heat
endothermic
chemical reaction that requires a net input of energy
amino acid
molecule that makes up proteins; made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur
catalyst
substance that decreases activation energy and increases reaction rate in a chemical reaction
enzyme
protein that catalyzes chemical reactions in organisms
substrate
reactant in a chemical reaction upon which an enzyme acts