Exam 2 Vocab

Question 0

Activation energy

Answer 0

Energy required to initiate a chemical reaction

Question 1

Enzyme catalysis

Answer 1

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

Question 2

Transition state

Answer 2

Intermediate stage in a chemical reaction, of higher free energy than the initial state, through which reactants must pass before giving rise to products

Question 3

Metastable state

Answer 3

Condition where potential reactants are thermodynamically unstable but have insufficient energy to exceed the activation energy barrier for the reaction

Question 4

Three properties of a catalyst

Answer 4

1. A catalyst increases the rate of a reaction by lowering the activation energy requirement
2. 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
3. A catalyst changes only the rate at which equilibrium is achieved

Question 5

Catalase

Answer 5

Enzyme that speeds the decomposition reaction of hydrogen peroxide to oxygen and water

Question 6

Ribozymes

Answer 6

An RNA molecule with catalytic activity

Question 7

Active site

Answer 7

Region of an enzyme molecule at which the substrate binds and the catalytic event occurs; also called the catalytic site

Question 8

Prosthetic groups

Answer 8

Small organic molecule or metal ion component of an enzyme that plays an indispensable role in the catalytic activity of the enzyme

Question 9

Coenzymes

Answer 9

Small organic molecule that functions along with an enzyme by serving as a carrier of electrons or function groups

Question 10

Substrate specificity

Answer 10

Ability of an enzyme to discriminate between very similar molecules

Question 11

Hydrogenation

Answer 11

Addition of electrons plus hydrogen ions (protons) to an organic molecule; reduction

Question 12

Group specificity

Answer 12

Ability of an enzyme to act on any of a whole group of substrates as long as they possess some common structural feature

Question 13

Denaturation

Answer 13

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

Question 14

Substrate activation

Answer 14

Role of an enzyme’s active site in making a substrate molecule maximally reactive by subjecting to the appropriate chemical environment for catalysis

Question 15

Enzyme kinetics

Answer 15

Quantitative analysis of enzyme reaction rates and the manner in which they are influenced by a variety of factors

Question 16

Initial reaction velocity

Answer 16

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

Question 17

Saturation

Answer 17

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

Question 18

Substrate concentration

Answer 18

Amount of substrate present per unit volumes at the beginning of a chemical reaction

Question 19

Michaelis constant (Km)

Answer 19

Substrate concentration at which an enzyme-catalyzed reaction is proceeding at one-half of its maximum velocity

Question 20

Maximum velocity (Vmax)

Answer 20

Upper limiting reaction rate approached by an enzyme-catalyzed reaction as the substrate concentration approaches infinity