Enzyme Models: Myoglobin & Hemoglobin, Enzymatic Catalysis, and Reaction Rates

These flashcards cover key concepts from the lecture notes on Myoglobin and Hemoglobin structures and functions, enzymatic catalysis mechanisms, and enzyme kinetics, including definitions and important terms.

Myoglobin (Mb)

Monomeric protein that stores oxygen in muscle with a very high oxygen affinity.

Hemoglobin (Hb)

Tetrameric protein that transports oxygen from lungs to tissues and carries CO2 and H+, exhibiting cooperative binding.

Oxygen Binding Curve

Graph showing the relationship between oxygen saturation and partial pressure of oxygen; myoglobin displays hyperbolic, and hemoglobin displays sigmoidal curves.

Cooperativity

Phenomenon where binding of oxygen to one subunit of hemoglobin increases affinity of remaining subunits.

T-state (tense state)

Conformation of hemoglobin or myoglobin when deoxygenated, exhibiting low affinity for oxygen.

R-state (relaxed state)

Conformation of hemoglobin or myoglobin when oxygenated, exhibiting high affinity for oxygen.

Bohr Effect

Effect wherein low pH stabilizes the T-state of hemoglobin, promoting oxygen release.

Cofactor

Non-protein helper that assists enzymes, such as metal ions, e.g., Fe2+ in heme.

Coenzyme

Small organic molecule that assists enzymes, typically derived from vitamins.

Michaelis-Menten Equation

Equation that predicts the reaction rate based on substrate concentration, indicating enzyme efficiency.

Km (Michaelis constant)

Substrate concentration at which the reaction rate is half of Vmax, indicating enzyme-substrate affinity.

Vmax

Maximum reaction velocity achieved by an enzyme when fully saturated with substrate.

Competitive Inhibition

Type of inhibition where an inhibitor binds to the active site, competing with the substrate, leading to an increase in Km without affecting Vmax.

Uncompetitive Inhibition

Type of inhibition where an inhibitor binds to the enzyme-substrate complex, decreasing both Km and Vmax.

Transition State

High-energy state in a chemical reaction that must be attained for reactants to be converted into products.

Acid-Base Catalysis

Catalytic mechanism where the transfer of protons is utilized to facilitate chemical reactions.

Serine Proteases

Enzyme family characterized by a serine residue at the active site, known for their role in peptide bond cleavage.

Transition-State Stabilization

Mechanism where enzymes bind the transition state more tightly than the substrate in order to lower activation energy.

Cysteine Proteases

Enzymes that utilize a cysteine residue as a nucleophile, similar to the mechanism of serine proteases.

Lineweaver-Burk Plot

Double reciprocal plot used to determine Km and Vmax from enzyme kinetic data, helping identify types of inhibition.