Peroxidase is an enzyme that breaks down hydrogen peroxide. The pH level impacts peroxidase function by affecting its structure and catalytic activity in several ways. Optimal peroxidase activity occurs within a specific pH range, typically acidic to neutral, depending on the source. Changes in pH alter the enzyme's structure and the ionization of amino acids in its active site, disrupting substrate binding and catalytic activity. Deviating from the optimal pH reduces the reaction rate and can fully inactivate the enzyme.

1. how does pH impact the function of peroxidase? updated 2023
Enzymes: Form and Function Catalytic proteins Lower activation energy of
reaction Combine or break apart substrates Not used up in reaction End in –ase
Lactase
metabolizes lactose DNA Polymerase – polymerize nucleotides Substrate to
product 1 Energy of activation with enzyme Energy needed to run reaction without
an enzyme Temp & pH Changes in environmental conditions will alter enzyme
structure, and therefore alter its function
Enzyme activity measured by Initial reaction velocity (IRV) Amount of product
per time this is what you’re doing in today’s experiment Or could use amount of
product per degree (for a temperature graph) what is shown in the graph above
IRV = (slope of the graph) Reaction you will run: the reaction goes from clear to
brown peroxidase is not used up in reaction guaiacol gets oxidized; hydrogen
peroxide gets reduced This is a redox reaction; Think about how rust turns a
different color when iron is oxidized Baseline: Filtered water – are the enzyme
concentrations too weak/strong?
Question: how does pH impact the function of peroxidase? Hypothesis:
_______________________________________
Experiment: try at pH of 4, 7, and 10 guaiacol (clear) + H2O2 tetra guaiacol
(brown) + H20 peroxidase Experiment USE CORRECT PIPETTE FOR EACH

2. CHEMICAL Make sure to only take out 300 microliters of Guaiacol 100
microliters to .1 milliliter Get Guaiacol from me Prepare your blank to tare the
colorimeter – fill cuvette 2/3 full and make sure the clear side of cuvette is
perpendicular to the colorimeter’s light Don’t touch the clear sides (fingerprints are
a problem).
Micropipettes: Don’t turn upside down. 1st resistance to extract chemical; 2nd
resistance to eject chemical. Pay attention to units on pipette. Don’t reuse tips.
Before adding enzyme solution to test, have all of your supplies ready: your
colorimeter tared and ready to go Guaiacol, pH buffer, and H202 in a test tube
stopwatch Once
enzyme is added, quickly pour into cuvette and place in colorimeter, recording
every 15 sec. Input data into excel sheet for all of class to record Calculate IRV
using greatest difference between two adjacent points You will make a line graph
of our data using Excel (there will be 4 lines on graph) BRING THIS GRAPH
NEXT
WEEK TO CHECK CORRECTNESS! We will cover components of the lab report
following your lab practical next week You will have access to sample lab reports,
rubrics, instructions
Topic: Effects of pH on Peroxidase upcoming due dates: Materials and Methods –
due March 15th 11:59pm on Canvas Literature Review – due April 1st 11:59pm on

3. Canvas Introduction – due April 8th 11:59pm on Canvas entire lab report – due
April 22nd 11:59pm on Canvas Lab Report – due March 25th 11:59pm on Canvas
using Turning Next week: BSC110L LAB PRACTICAL covers labs: Topics 1-4
(scientific method, biomolecules, microscopes and cells, enzymes) worth 20% of
your grade! DO NOT arrive late no electronics on your person (phones, ear buds,
smartwatches in your bag) Written Exam: 40-45 questions on written portion 55
questions, 2 points each One or two stations for practical applications: I will be
monitoring you at these stations and giving you points upon satisfactory
completion (10-15 points) when complete: students can either turn their paper in or
revisit stations one at a time for a short period Revisit the PowerPoints for all of
the labs
Review the lab manual pages If we thought it was important enough to put in a
PowerPoint or cover it in a quiz or do it as an activity, it’s important enough to put
on the exam! Use the study guide found on Canvas Biology Tutoring (Walker
Science room 149) Tutoring for BSC 110/111: Monday 8am – 7pm Tuesday 8am –
11am
and 2:30pm – 5pm Wednesday 8am – 5pm Thursday 8am – 11am and 2:30pm –
3:30pm Friday 9am – 10:30am Tutoring for BSC 107/250/251: Monday 10am –
12pm Wednesday 10am – 12pm Thursday 5:30pm – 7pm Friday 8am –

4. 12pm A graduate student will be present who can help with lab reports during the
following times: Tuesday 10am – 12pm and 2pm – 5pm Wednesday 10am – 12pm
and 2pm – 5pm Thursday 10am – 12pm and 2pm – 5pm Friday 10am – 12pm
From the syllabus: Students arriving more than 15 minutes late for a lab practical
will
not be allowed to take the practical during the allotted time. If a suitable excuse is
provided to the teaching assistant and approved by the lab coordinator, a make-up
Peroxidase is an enzyme
that plays a crucial role in various biological processes, particularly in the
breakdown of hydrogen peroxide (H2O2) into water and oxygen. The pH level can
significantly impact the function of peroxidase enzymes, as it affects their overall
structure and catalytic activity.
1. Optimal pH: Peroxidase enzymes exhibit optimal activity at specific pH
levels. The optimal pH varies depending on the specific peroxidase enzyme
and its source, but commonly falls within the acidic to neutral range. For
example, peroxidase enzymes derived from plants often have an optimal pH
around 6.0-7.0, while peroxidases from other sources may have slightly
different optimal pH ranges.

5. 2. Enzyme Structure: The pH directly influences the structure of peroxidase
enzymes. These enzymes are globular proteins composed of amino acids.
Changes in pH alter the electrostatic interactions between amino acid
residues, resulting in modifications to the enzyme’s three-dimensional
structure.
3. Ionization of Functional Groups: pH affects the ionization states of specific
functional groups within the peroxidase enzyme. A change in pH alters the
charges on amino acid side chains, including histidine, aspartic acid, and
glutamic acid residues, which can impact the enzyme’s active site and
substrate binding.
4. Active Site Configuration: The active site of peroxidase enzymes is where
the catalytic reaction occurs. pH variations can affect the active site
configuration, influencing the enzyme’s ability to bind to its substrate and
facilitate the catalytic reaction. pH changes can disrupt the precise
arrangement of amino acids within the active site, leading to reduced
enzyme activity.
5. Catalytic Activity: The rate of peroxidase enzyme-catalyzed reactions can be
significantly influenced by pH. Deviating from the optimal pH range can
reduce the catalytic activity of the enzyme, resulting in slower reaction rates.

6. As the pH moves further away from the optimal range, the enzyme activity
may diminish to the point of complete inactivation.
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