Chapter 16 Flashcards
activation energy
the minimum energy with which molecules must collide to react
active site
the region of an enzyme formed by specific amino-acid side chains at which catalysis occurs
Arrhenius equation
an equation that expresses the exponential relationship between temperature and the rate constant: k = Ae^-Ea/RT
average rate
the change in concentration of reactants (or products) divided by a finite time period
biomolecular reaction
an elementary reaction involving the collision of two reactant species
catalyst
a substance or mixture that increases the rate of a reaction without being used up in the process
chemical kinetics
the study of the rates of reactions and the factors that affect them
collision theory
a model that explains reaction rate as based on the number, energy, and orientation of colliding particles
effective collision
a collision in which the particles meet with sufficient energy and an orientation that allows them to react
elementary reaction (elementary step)
a simple reaction that describes a single molecular event in a proposed reaction mechanism
enzyme
a biological macromolecule (usually a protein) that acts as a catalyst
enzyme substrate complex
the intermediate in an enzyme-catalyzed reaction, which consists of enzyme and substrate(s) and whose concentration determines the rate of product formation
frequency factor
the product of the collision frequency Z and an orientation probability factor p that is specific for a reaction
half-life
in chemical processes, the time required for the reactant concentration to reach half of its initial value. In nuclear processes, the time required for half the initial number of nuclei in a sample to decay
heterogeneous catalyst
a catalyst that occurs in a different phase from the reactants, usually a solid interacting with gaseous or liquid reactants
homogeneous catalyst
a catalyst (gas, liquid, or soluble solid) that exists in the same phase as the reactants
hydrogenation
the addition of hydrogen to a carbon-carbon multiple bond to form a carbon-carbon single bond
induced fit model
a model of enzyme action that pictures the binding of the substrate as inducing the active site to change its shape and become catalytically active
initial rate
the instantaneous rate at the moment the reactants are mixed, that is, at t = 0
instantaneous rate
the reaction rate at a particular time, given by the slope of a tangent to a plot of reactant concentration vs. time
integrated rate law
a mathematical expression for reactant concentration as a function of time
lock and key model
a model of enzyme function that pictures the enzyme active site and the substrate as rigid shapes that fit together as a lock and key, respectively
molecularity
the number of reactant particles involved in an elementary step
rate constant (k)
the proportionality constant that relates reaction rate to reactant (and product) concentrations
