1) This document discusses enzyme kinetics and multi-step biochemical reactions. It defines key terms like enzymes, reactants, products, elementary steps, and intermediate products. 2) It explains that some biochemical reactions occur in a single step but others require multiple steps, with intermediate products forming in between. The series of steps that produce intermediates is called a multi-step reaction. 3) Within a multi-step reaction, the slowest step that determines the overall rate is the rate-limiting step. Examples are provided to illustrate multi-step reactions and identifying the rate-limiting step.

1. Biochemistry
Enzyme Kinetics:
Multi Step Reaction & Rate limiting Steps
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L.VENKATESH,
I Msc Microbiology,
Department of Biology,
Gri,Dindigul,
Tamil Nadu.

2. Introduction
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 In the living world without the biochemical reaction
nothing will happened, These chemical reaction was speedup
by enzymes, if there is no enzymes a reaction was take million
years to complete.
 Some biochemical reaction is completed within one step
but in some causes it will take more step to complete the whole
reaction, these elementary step reaction called multi step
reaction.
 In multi step reaction which elementary step was take more
time to completed that is called rate determine step.

3. Vocabulary
Enzyme:
Enzyme is a protein produced by living cells, which
catalyzes or speedup a biochemical reaction.
Enzyme Kinetics:
Enzyme kinetics is a study or understanding the
rate of biochemical reaction in a cell.
Reactants:
The starting materials in a reaction that undergo a
chemical change to form a product.
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4. Vocabulary
Elementary step:
An elementary step is a single and simple step in
a multistep reaction.
Intermediate product:
The product of single elementary step in multi
step biochemical reaction.
Products:
The final changes of reactant its called product.
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5. 5
Reactant -------------------- Products
Mechanism
Some biochemical reaction finished with only one
step, but in some causes it will take two or more
intermediate step for producing a new product these
intermediate step reaction is called multi step reaction.
The series reactions producing intermediate
products is called a multi step reaction

6. Common role
In generally, almost every biochemical multi step
reaction, following steps are take place,
 Step1– previous bonds are broken
 Step2 – colliding of two molecules, Activation energy(Ea),
enough Speed
 Step3 - new bond formation
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7. Examples:
 C + O2 CO2
 H2 + I2 2HI
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O2 O + O (S1)
C + O CO (S2)
CO + O CO2 (S3)
H2 H + H (S1)
I2 I + I (S2)
H + I HI (S3)
H + I HI (S4)
HI + HI 2HI (S5)

8. NO2(g) +NO2(g) NO3(g) + NO(g) (step1)
NO3(g) + CO(g) NO2(g) + CO2(g) (step2)
NO2(g) + CO(g) NO(g) + CO2(g) (overall reaction)
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9. Rate limiting step(time)
Faster reaction = less time = faster rate
Slower reaction = more time = slower rate
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The slowest step in a multi step reaction is called
Rate limiting step, which determine the over all
rate of the reaction

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Examples: Car Washing station,
(Stage 1)
(Stage 2)
(Stage 3)
In an one car washing station three stages are there, among that 1st
stage is car wetting and take 7 minutes, stage 2 is cleaning and take
14min, stage 3 is only drying and take 7 minutes,,, among these three
stages the stage 2 taking more time so it is determine the whole timing of
the car washing process, if these are had a same time there is no time
issues,,,
So in these process stage 2 is time determine step or rate limiting step.

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NO2 +NO2 NO3 + NO (step 1) (slow)
NO3 + CO NO2+ CO2 (step 2) (fast)
NO2 + CO NO + CO2 (overall reaction)
NO2 + CO
NO + CO2
Step 1
Step 2

12. Difference between multi step reaction & rate
limiting step
 Both multi step reaction and rate limiting steps are
almost similar, but in some way it have a difference
 In a reaction, the elementary steps had no time or
rate different with each other(same time) it is called
multi step reaction
 In a reaction, the elementary steps had time or rate
different with each other(different time) it is called
rate limiting step
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13. Reference
 https://www.ck12.org/book/ck-12-chemistry-second-
edition/r9/section/18.5/
 http://www.youtube.com/watch?v=-ctr9MUM_hI
 https://youtu.be/l4VCiJulLKw?si=Ysg_WUGSCtf9s4O
X
 https://youtu.be/ShzW1LoQgoc?si=C7sc6Khnvq8XJjd
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14. Thank you
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