Biochemistry - The Behavior of Proteins: Enzymes

These flashcards cover key terms and concepts related to enzymes and their behavior in biochemical reactions.

Biological catalysts, usually globular proteins, that increase the rate of a reaction.

Enzyme

A substance that increases the rate of a reaction without being consumed.

Catalyst

The speed at which reactants are converted into products.

Reaction Rate

Molecules with the same molecular formula but different spatial arrangements.

Stereoisomers

The difference between energies of reactants and products under standard conditions.

Standard Free Energy Change (\Delta G^\circ)

Energy input required to initiate a reaction.

Activation Energy (\Delta G^{\circ\ddagger})

An intermediate state in a reaction where old bonds break and new bonds form.

Transition State

A ratio that describes the concentration of reactants and products at equilibrium.

Equilibrium Constant

The temporary complex formed when an enzyme binds to its substrate.

Enzyme-Substrate Complex

The model describing how a substrate fits precisely into the active site of an enzyme.

Lock-and-Key Model

Describes how the binding of substrate induces a change in the enzyme's conformation.

Induced Fit Model

The region of an enzyme where substrate molecules bind and undergo a chemical reaction.

Active Site

Forces that facilitate the binding of substrates to enzymes, including hydrogen bonds and electrostatic attractions.

Noncovalent Forces

Substances that bind to an enzyme and can be released.

Reversible Inhibitors

Inhibition caused by a substance that competes with the substrate for the active site.

Competitive Inhibition

Inhibition where a substance binds to an enzyme at a site other than the active site.

Noncompetitive Inhibition

Inactivation of an enzyme due to covalent binding of an inhibitor.

Irreversible Inhibition

Molecules that bind irreversibly to enzymes to inactivate them.

Suicide Substrates

A type of noncovalent interaction important in enzyme-substrate binding.

Hydrogen Bonding

Interactions between charged groups that contribute to enzyme activity.

Electrostatic Attractions

Weak attractions between molecules or parts of molecules that contribute to enzyme stability.

Van der Waals Attractions

The process by which an enzyme's structure is altered, rendering it inactive.

Enzyme Denaturation

The maximum rate of reaction for an enzyme-catalyzed process.

V_{max}

Michaelis constant, representing the substrate concentration (S) at which the rate is half of V_{max}.

K_M

A double-reciprocal plot used to determine kinetic parameters of enzymes by plotting 1/v vs 1/S.

Lineweaver–Burk Plot

Represents the ratio of KM/V{max} in enzyme kinetics.

Slope of Lineweaver–Burk Plot

Represents the reciprocal of V{max} (1/V{max}) on a Lineweaver–Burk plot.

Y-Intercept of Lineweaver–Burk Plot

Indicates a decrease in substrate affinity commonly observed under competitive inhibition.

K_M increased

Loss of enzyme activity due to binding of an inhibitor or structural damage.

Enzyme Inactivation

Alteration in the shape of an enzyme upon substrate binding or environmental change.

Conformational Change

Chemical processes that occur within living organisms.

Biochemical Reactions

The relationship between temperature and the rate of enzymatic reactions, often featuring an optimal point.

Temperature Dependence

The energy available to perform work during a chemical reaction.

Free Energy

Molecules similar to substrates that can inhibit enzyme activity by occupying the binding site.

Substrate Analogues

The specific region of an enzyme where the substrate binds.

Binding Site

The amount of substrate present in the reaction mixture, usually denoted as S.

Substrate Concentration

The amount of inhibitor present in the reaction environment, usually denoted as I.

Inhibitor Concentration

Quantitative measures of enzyme activity, including KM and V{max}.

Kinetic Parameters

The formation of a strong chemical bond between an inhibitor and an enzyme, typical of irreversible inhibition.

Covalent Binding

A reversible inhibitor of bacterial enzymes (transpeptidases) that stops cell wall growth.

Antibiotic Penicillin

The assembly of an enzyme with its substrate to form an enzyme-substrate (ES) complex.

Complex Formation

The change in free energy of reactants and products during an enzyme-mediated reaction.

Free Energy Change in Catalysis

The ability of an enzyme to select its substrate from a range of potential candidates.

Specificity of Enzymes

A part in the reaction pathway where bonds are being formed and broken, such as the transition state.

Intermediate Stage

Enzymes that regulate and accelerate biochemical reactions within living organisms.

Biological Catalysts

Type of inhibition where noncompetitive does not compete for the active site, while competitive does.

Noncompetitive vs Competitive Inhibition

The energy released during the binding of a substrate to an enzyme's active site.

Substrate Binding Energy

The step-by-step sequence of elementary reactions by which the overall chemical change occurs.

Reaction Mechanism

Defined as the constant k{cat}/KM, reflecting how efficiently an enzyme converts substrate to product.

Enzyme Efficiency