Factors That Affect the Rate of Reaction of Peroxidase

Factors that Affect the Rate of Reaction of Peroxidase
Purpose: To determine the effect of various factors on the rate of reaction between an enzyme and its substrate, and also to determine the optimal ranges under which the enzyme activity is maximized. Also to determine whether saline and alcohol are inhibitors or activators
Hypothesis: PH factor prediction: I predict that as the pH increases so the activity of the enzyme will increase until it reaches optimum pH range (pH 7) because the enzyme is less denatured when it reaches the preferred pH level, and after this, it will decrease because the active site will change in shape and it will no longer accept substrates.
Temperature factor prediction: I predict as the temperature increases, the enzyme activities will increase because there is more energy to speed up the reaction until it reaches the optimum temperature range (room temperature which is about 20 °C), and after that, the enzyme activities will decrease because of denaturing of the enzymes (cause changes to the active site that will no longer fit substrate)
The concentration of enzymes prediction: I predict that as the concentration of enzyme increases, so the enzyme activities will increase because there is more enzyme to react with the substrates however when enzymes get saturated, the reaction will come to a plateau because eventually all the substrates will have enzymes to react with, and any extra will have no effect on the reaction whatsoever. I predict alcohol is an inhibitor of Peroxidase because alcohol when alcohol bind to the allosteric site it changes the active site shape of the enzymes thus deactivating enzymatic activities
I predict salt is an activator of Peroxidase because salt contains Na ions which attach to the allosteric site changing the shape of the enzyme to fit a substrate.
Materials:
Peroxidase (enzyme in potato)
Hydrogen peroxide, 3%
A strong acid, pH3 (lemon juice, or HCL) 0. 5
A strong base, pH 10 (drain cleaner, NaOH) 0. 5 mol/L
A weak acid, pH 6 (vinegar, acetic acid( CH3COOH)) 0. 5 mol/L
A weak base, pH 8 (baking soda, sodium bicarbonate (NaHCO3)) 0. 5 mol/L a
A saline solution, pH 7 (table salt, NaCl) 0. mol/L
Alcohol, pH 7 (rubbing or spirits (isopropyl or ethanol)) 1 mol/L
Distilled water, pH 7
Hot plate, stove, or kettle (hot water bath)
Coldwater (ice water bath)
Eyedropper or oral, needle-less syringe 10 ccs (10 mL)
Graduated cylinder or needle-less syringe 10 ccs ( 10 mL)
Disposable plastic plates
Disposable plastic cups
Thermometer
Timing device (with a second hand)
Ice Safety Precautions Being sure to wash hands before and after handling materials. Use caution with hot and cold materials.
Follow all safety procedures. Procedure: 
I placed a piece of raw potato in 10 mL of water at room temperature (20 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel)
I placed a piece of raw potato in 10 mL of cold water at a temperature of 10 °C for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of temperature on reaction activity
I placed a piece of raw potato in 10 mL of cold water at a temperature of 15 °C for three minutes.
Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of temperature on reaction activity
I placed a piece of raw potato in 10 mL of hot water at room temperature of 25 °C for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of temperature on reaction activity
I placed a piece of raw potato in 10 mL of hot water at a temperature of 30 °C for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of temperature on reaction activity I placed a piece of raw potato in 10 mL of lemon juice 0. 5 mol/L at room temperature (21 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of pH on reaction activity
I placed a piece of raw potato in 10 mL of drain cleaner, NaOH at room temperature (21 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of pH on reaction activity
I placed a piece of raw potato in 10 mL of vinegar, acetic acid 0. mol/L at room temperature (21 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of pH on reaction activity
I placed a piece of raw potato in 10 mL of baking soda 0. 5 mol/L at room temperature (21 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to observe the effect of pH on reaction activity
I placed a piece of raw potato in 10 mL of saline solution 0. 5 mol/L at room temperature (21 °C) for three minutes.
Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to determine if saline is an inhibitor or activator
I placed a piece of raw potato in 10 mL of alcohol solution 1 mol/L at room temperature (21 °C) for three minutes. Put three drops of hydrogen peroxide (3 %) on it (after dabbing dry with a paper towel) to determine if alcohol is an inhibitor or activator
I put three drops of hydrogen peroxide (3 %) on large pieces of potato to observe the effect of concentration (large pieces have a smaller surface area which has fewer enzymes) I put three drops of hydrogen peroxide (3 %) on medium pieces of potato to observe the effect of concentration (large pieces have a smaller surface area which has fewer enzymes)
I put three drops of hydrogen peroxide (3 %) on small pieces of potato to observe the effect of concentration (smaller pieces have a larger surface area which has more enzymes, the more the enzymes the greater the reaction activity)
Analysis: Inquiry skills (scientific Method): The dependant variable is time The independent variable is a Peroxidase enzyme
The controlled variables are PH, temperature, and concentration The reason to create this datum is so that we could make a comparison. Without creating this action, it would be hard to see the effect of enzymes on the decomposition of peroxide. It’s to create this reference point to see how it decomposes before any enzymatic reaction and after. It seems to be that Catalase has stronger hydrogen and ionic bonds than Peroxidase and that’s why it can withstand more temperature before it’s denatured. Conclusion: My experiment results agrees with my hypothesis. According to the data tables I have created, you notice that the enzymatic reaction (amount of bubbles) first increases starting from 15°C then it starts to go down when it reaches over 25°C (this matches with my first prediction on the effect of temperature on Peroxidase) Starting from pH 3 to pH 7, the reaction increases then it decreases after pH 7 (this matches with second prediction) Starting from low concentration, we get less reaction then it increases gradually (this matches with my third prediction).

Prof. Angela

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