Exam 2 Vocab Flashcards
(21 cards)
Activation energy
Energy required to initiate a chemical reaction
Enzyme catalysis
Involvement of an organic molecule, usually a protein but in some cases RNA, in speeding up the rate of a specific chemical reaction or class of reactions
Transition state
Intermediate stage in a chemical reaction, of higher free energy than the initial state, through which reactants must pass before giving rise to products
Metastable state
Condition where potential reactants are thermodynamically unstable but have insufficient energy to exceed the activation energy barrier for the reaction
Three properties of a catalyst
- A catalyst increases the rate of a reaction by lowering the activation energy requirement
- A catalyst acts by forming transient, reversible complexes with substrate molecules, binding them in a manner that facilitates their interaction and stabilizes the intermediate transition state
- A catalyst changes only the rate at which equilibrium is achieved
Catalase
Enzyme that speeds the decomposition reaction of hydrogen peroxide to oxygen and water
Ribozymes
An RNA molecule with catalytic activity
Active site
Region of an enzyme molecule at which the substrate binds and the catalytic event occurs; also called the catalytic site
Prosthetic groups
Small organic molecule or metal ion component of an enzyme that plays an indispensable role in the catalytic activity of the enzyme
Coenzymes
Small organic molecule that functions along with an enzyme by serving as a carrier of electrons or function groups
Substrate specificity
Ability of an enzyme to discriminate between very similar molecules
Hydrogenation
Addition of electrons plus hydrogen ions (protons) to an organic molecule; reduction
Group specificity
Ability of an enzyme to act on any of a whole group of substrates as long as they possess some common structural feature
Denaturation
Loss of the natural three-dimensional structure of a macromolecule, usually resulting in a loss of biological activity; caused by agents such as heat, extremes of pH, urea, salt, and other chemicals
Substrate activation
Role of an enzyme’s active site in making a substrate molecule maximally reactive by subjecting to the appropriate chemical environment for catalysis
Enzyme kinetics
Quantitative analysis of enzyme reaction rates and the manner in which they are influenced by a variety of factors
Initial reaction velocity
Reaction rate measured over a period of time during which the substrate concentration has not decreased enough to affect the rate and the accumulation of product is still too small to cause any measurable back reaction
Saturation
Inability of higher substrate concentrations to increase the velocity of an enzyme-catalyzed reaction beyond a fixed upper limit determined by the finite number of enzyme molecules available
Substrate concentration
Amount of substrate present per unit volumes at the beginning of a chemical reaction
Michaelis constant (Km)
Substrate concentration at which an enzyme-catalyzed reaction is proceeding at one-half of its maximum velocity
Maximum velocity (Vmax)
Upper limiting reaction rate approached by an enzyme-catalyzed reaction as the substrate concentration approaches infinity
