In enzyme kinetics, the term “quasi steady state” is also known as what (context: Briggs–Haldane treatment of the Michaelis–Menten mechanism)?

Introduction:
The phrase “quasi steady state” appears in the refined treatment of enzyme kinetics where the enzyme–substrate complex concentration is assumed to change slowly after a brief transient. This question checks whether you know the synonymous terminology used for this foundational approximation.

Given Data / Assumptions:

• We are analyzing the Michaelis–Menten scheme under typical initial-rate conditions.
• We focus on the concentration of the ES complex after the initial pre-steady-state.
• Historical context: Michaelis–Menten (1913) vs Briggs–Haldane (1925).

Concept / Approach:
The “quasi steady state” is commonly termed the “pseudo steady state” approximation (PSSA). Briggs and Haldane formalized the approach where d[ES]/dt ≈ 0 after an initial transient, allowing derivation of the Michaelis–Menten rate law without requiring rapid equilibrium between E, S, and ES. Hence, “quasi” and “pseudo” steady state are interchangeable labels for this assumption.

Step-by-Step Solution:
Recognize that quasi steady state refers to d[ES]/dt ≈ 0 during the main part of the reaction.Connect this to the Briggs–Haldane formalism that generalizes beyond the rapid-equilibrium assumption.Identify the accepted synonym: “pseudo steady state.”

Verification / Alternative check:
Textbooks and reviews consistently use “quasi steady state” and “pseudo steady state” interchangeably, while attributing the formal treatment to Briggs–Haldane rather than the original rapid-equilibrium assumption of Michaelis–Menten.

Why Other Options Are Wrong:
Michaelis–Menten approach: classically tied to rapid equilibrium, not the generalized steady-state argument.
Briggs–Haldane approach: it formalized the method but is not itself the synonym asked; the standard synonym is “pseudo steady state.”
All of the above: incorrect because the Michaelis–Menten approach is not a synonym for quasi steady state.

Common Pitfalls:

• Equating rapid equilibrium with steady-state treatment.
• Memorizing names without understanding the underlying d[ES]/dt ≈ 0 condition.

Final Answer:
Pseudo steady state