MM Assumptions

0.0(0)
Studied by 2 people
call kaiCall Kai
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
GameKnowt Play
Card Sorting

1/4

flashcard set

Earn XP

Description and Tags

List of MM assumptions and what happens when they fail

Last updated 3:42 AM on 5/22/26
Name
Mastery
Learn
Test
Matching
Spaced
Call with Kai

No analytics yet

Send a link to your students to track their progress

5 Terms

1
New cards

Assumption #1

No product is present at the start of catalysis

When it fails:

  • the reverse reaction becomes significant

  • product can rebind to the active site and act like a competitive inhibitor

  • the forward run would slow down

  • the rate measured is no longer the true initial velocity

<p>No product is present at the start of catalysis</p><p></p><p>When it fails:</p><ul><li><p>the reverse reaction becomes significant</p></li><li><p>product can rebind to the active site and act like a competitive inhibitor</p></li><li><p>the forward run would slow down</p></li><li><p>the rate measured is no longer the true initial velocity</p></li></ul><p></p>
2
New cards

Assumption #2

The rate of formation of the ES complex is equal to the rate of dissociation plus breakdown

When it fails:

  • if steady state is not maintained then [ES] is still building up OR [ES] is declining

  • if it is still building up, then the run is still in pre-steady state phase and the ES complex is still accumulating!

  • if it is declining, the substrate is being depleted and there would be less substrate available to form new ES

  • for both scenarios the Vo measurement would be inaccurate

<p>The rate of formation of the ES complex is equal to the rate of dissociation plus breakdown </p><p></p><p>When it fails: </p><ul><li><p>if steady state is not maintained then [ES] is still building up OR [ES] is declining</p></li><li><p>if it is still building up, then the run is still in pre-steady state phase and the ES complex is still accumulating!</p></li><li><p>if it is declining, the substrate is being depleted and there would be less substrate available to form new ES</p></li><li><p>for both scenarios the Vo measurement would be inaccurate</p></li></ul><p></p>
3
New cards

Assumption #3

The concentration of substrate is greater than the concentration of free enzyme

When it fails:

  • enzyme molecules are present in amounts comparable to or exceeding substrate

  • this assumption is directly linked to assumption 2 (steady state requires [S]»[E]

    • both assumption #2 and #3 fail together

  • [ES] never stabilizes, it rises and falls too quicly

  • steady state breaks down simultaneously

  • Km and Vmax are underestimated and unreliable

<p>The concentration of substrate is greater than the concentration of free enzyme</p><p></p><p>When it fails:</p><ul><li><p>enzyme molecules are present in amounts comparable to or exceeding substrate</p></li><li><p>this assumption is directly linked to assumption 2 (steady state requires [S]»[E]</p><ul><li><p>both assumption #2 and #3 fail together</p></li></ul></li><li><p>[ES] never stabilizes, it rises and falls too quicly</p></li><li><p>steady state breaks down simultaneously </p></li><li><p>Km and Vmax are underestimated and unreliable </p></li></ul><p></p>
4
New cards

Assumption #4

Only the initial velocity of the steady state reaction is measured

When it fails:

  • substrate is depleted

    • enzymes see less S than you think and the rate appears lower than it should for a certain [S]

  • product accumulates

    • [P] is no longer = 0, so the product can rebind to the active site (causing product inhibition)

    • the reverse reaction becomes significant and slows down the observed rate

  • steady state breaks down

    • as [S] drops, ES complex started to decline

    • MM equation is no longer valid

  • enzyme may be unstable

    • overtime an enzyme can denture or degrade

    • there is less functional enzyme available

    • random rate drops unrelated to kinetics

<p>Only the initial velocity of the steady state reaction is measured</p><p></p><p>When it fails:</p><ul><li><p>substrate is depleted</p><ul><li><p>enzymes see less S than you think and the rate appears lower than it should for a certain [S]</p></li></ul></li><li><p>product accumulates</p><ul><li><p>[P] is no longer = 0, so the product can rebind to the active site (causing product inhibition)</p></li><li><p>the reverse reaction becomes significant and slows down the observed rate</p></li></ul></li><li><p>steady state breaks down</p><ul><li><p>as [S] drops, ES complex started to decline</p></li><li><p>MM equation is no longer valid</p></li></ul></li><li><p>enzyme may be unstable</p><ul><li><p>overtime an enzyme can denture or degrade</p></li><li><p>there is less functional enzyme available </p></li><li><p>random rate drops unrelated to kinetics</p></li></ul></li></ul><p></p>
5
New cards

Assumption #5

Enzyme is present as either a free enzyme or as the ES complex

When it fails:

  • the mass abalone equation breaks down since some enzyme is unaccounted for, the MM equations does not recognize this

  • scenario #1: Inhibitor is Present

    • Inhibitor binds to enzyme or ES and now the enzyme exists as E, ES, EI, and/or ESI

    • Standard MM equation is no longer valid

  • scenario #2: Product is still bound (EP complex)

    • Enzyme is temporary stuck as EP complex (relevant in multi-step rxns)

    • EP is a third state that the MM equation ignores

  • scenario #3: Multiple Substrates (ternary complex)

    • Bisubstrate rxns and enzyme can exist as E, EA, EB, EAB

    • Basic MM only handle one substrate

  • scenario #4: Enzyme Denaturation or Aggregation

    • some enzymes become inactive through denaturation and they are lost from the system

    • calculations would be wrong due to the nonfunctional enzyme being accounted for

  • scenario #5: Allosteric Enzymes

    • allosteric enzymes can exists but MM equation fails for allosteric enzymes (hence sigmoidal kinetics w/allosteric instead of hyperbolic)

<p>Enzyme is present as either a free enzyme or as the ES complex</p><p></p><p>When it fails:</p><ul><li><p>the mass abalone equation breaks down since some enzyme is unaccounted for, the MM equations does not recognize this</p></li><li><p>scenario #1: Inhibitor is Present</p><ul><li><p>Inhibitor binds to enzyme or ES and now the enzyme exists as E, ES, EI, and/or ESI</p></li><li><p>Standard MM equation is no longer valid</p></li></ul></li><li><p>scenario #2: Product is still bound (EP complex)</p><ul><li><p>Enzyme is temporary stuck as EP complex (relevant in multi-step rxns)</p></li><li><p>EP is a third state that the MM equation ignores</p></li></ul></li><li><p>scenario #3: Multiple Substrates (ternary complex)</p><ul><li><p>Bisubstrate rxns and enzyme can exist as E, EA, EB, EAB</p></li><li><p>Basic MM only handle one substrate</p></li></ul></li><li><p>scenario #4: Enzyme Denaturation or Aggregation</p><ul><li><p>some enzymes become inactive through denaturation and they are lost from the system</p></li><li><p>calculations would be wrong due to the nonfunctional enzyme being accounted for</p></li></ul></li><li><p>scenario #5: Allosteric Enzymes</p><ul><li><p>allosteric enzymes can exists but MM equation fails for allosteric enzymes (hence sigmoidal kinetics w/allosteric instead of hyperbolic)</p></li></ul></li></ul><p></p>