Effect on Enzyme Activity

EFFECT OF TEMPERATURE,PH AND SUBSTRATE CONCENTRATION ON ENZYME ACTIVITY |

Aim To investigate the effect of Temperature,Ph and substrate concentration on the rate of enzyme activity.
Hypothesis That only a certain, temperature,ph and concentration will the enzyme’s activity be at its optimum, this is being the right environment for it to function.
Part A – Effect of temperature on Rennin
Intro Temperature affects the rate at which molecules collide with each other.An increase in temperature will inturn increase activity and rate of reacton.Enzymes only work at a specific temperature.Enzymes are specially folded to form active sites of a specific shape, and high temperatures can change the shape of the active sites, causing enzyme to be denatured..Rennin is enzyme found in stomach of mammals that helps solidiy milk.
Materials
* Rennin solution * 120ml of milk * 12 Test tubes * Stopwatch * Test tube rack * Measuring cylinder * Water bath * Ice * Thermometer
Method
1. Give each test tube a number from 1-12. 2. In each test tube place 10ml of milk. 3. Place test tubes 1-4 in ice water. 4. Measure the temperature of the water and record results in table. 5. Place 10 drops of rennin solution into test tubes 3 and 4.Test tubes 1 and 2 are controls and no rennin will be added to them. 6. Begin timing.Check if the milk has clotted in each test tube by removing from the ice water and tilting slightly every 30 seconds.If the milk has clotted it should not move. 7. Record the time taken for the milk to solidify completely for each test tube in the results table. 8. Place test tube 5—8 in a water bath of approximately 37oC. 9. Repeat steps 5-7 but leave test tubes 5 and 6 as conntrol’s – add no rennin.. 10. Place test tubes 9-12 in a water bath of approximately 80oC. 11. Repeat steps 5-7 but leave test tubes 9 and 10 as the controls- add no rennin. Results Temperature of Water Bath | Test Tuvbe Number | Time taken for Milk to Solidify (mins) | | 1 Control | - | | 2 Control | - | 0-10 | 3 Treatment | * 15 | | 4 Treatment | * 15 | | 5 Control | - | 37 | 6 Control | - | | 7 Treatment | 2 | | 8 Treatment | 2 | | 9 Control | - | 80 | 10 Coontrol | - | | 11 Teatment | * 15 | | 12 Treatment | * 15 |

The purpose of the control test tubes were too compare the results of the test tubes with rennin, and to justify that temperature has an effect on enzyme activity.From the results in the table the fastest reaction of clotting the milk occurred at 37o C, this was the optimum temperature for the activity of tyhr enzyme present in the stomach know as rennin.This is because the temperature of the stomach is 37o C,and it is at this temp that rennin actively clots milk in the stomach.Anything outside this temperate the enzyme activity decreased/denatured.

Part B – Effect of Change in Ph on Enzyme Catalase
Intro Ph affects the activity of an enzynme in a similar manner to that of temperature.Enzymes wil have a specific pH for optimum function.If enxzyme put into environment outside optimum ph , it will change the shape of the proteins that make up active site and denature the enzyme-decreasing activity.Catlase is an enzyme found in every cell of the human body.Cells produce hydrogen peroxide as a by product of cellular respiration.Hydrogen peroxide is toxic and needs to be broken down.Catalase breaks it down into water and oxygen.
Materials
* 6 x 1 cm3 cubes of cow liver/potato cubes * 1 mortar and pestle * 12 test tubes * Test tube rack * 30 cm rulr * 20 mL hydrogen peroxide * 20 mL 2M HCl * 20 mL 2M NaOH * 20 mL water * pH probe * Litimus paper

Method 1. Label the test tubes from 1-12 and place in the test tube rack. 2. Add 5 mL of hydrogen Peroxide solution to all the test tubes. 3. In Test tubes 1-4 add 5 mL of 2M HCl. 4. In test tubes 5-8 add 5 mL of 2M NaOH. 5. In test tubes 9-12 add 5 mL of water. 6. Using the pH probe and litimus paper measure the pH of each of the tubes. 7. Add 1cm3 of crushed liver or potato (use the mortar and pestle to do this) to test tubes 3 and 4. 8. Measure the level of bubbles that rise up in each of the test tubes and record them in the results table 9. Repeat with test tubes 7 and 8 , and then with test tubes 11 and 12.
Results
Test tube | pH of solution | Height (cm) of bubbles produced | 1 Control | 6 | 5 | 2 Control | 6 | 5 | 3 Treatment | 1 | 0.1 | 4 Treatment | 1 | 0.1 | 5 Control | 6 | 5 | 6 Control | 6 | 5 | 7 Treatment | 9 | 10 | 8 Treatment | 9 | 10 |

The purpose of the control test tubes were too compare the results of the test tubes with catalse, and to justify that pH has an effect on enzyme activity.From the results in the table the greatest reaction largets height was test tube 7 and 8 with a ph of 9 bubbling 10 cm.The pH of 9 was the optimum pH for the activity of the enzyme catalase present in all the bodies cells.This is because the of the body is basic at aroud 9 pH.It is at this pH that catalase actively actively breaks down toxic hydrogen peroxide, into hydrogen and oxygen.
2H2O2 Catalase 2H2O + O2

Part C – Effect of substrate concentration on Enzyme
Intro Effect of substrate concentration: initially, the more substrate you add will cause enzyme activity to increase, upto a certain point (activity doesn't increase infinitely). Once you've added enough substrated that all enzymes are being used, increasing substrate concentration any further would have no effect on activity.

So again, initially increasing substrate concentration would cause enzyme activity to increase but up to a maximum. Once you've added enough substrate to completely keep all the enzymes busy, adding any extra substrate has no effect on enzyme activity.

As the substate concentration is increased the rate of reaction increases.
There are more collisions between the substrate and the enzyme such that more activated complex's are formed and therefore product per unit time.
(b) Further increases in substrate also increase the rate but proportionately less than previously.
The number of occupied active site is increasing and there is competition for the active site.
(c) The rate is constant.
The enzyme active site is fully saturated with substrate such that adding more substrate does not increase the rate of reaction. The enzymes molecules are fully occupied converting substrate to product and any substrate must await a free active site before conversion to product.

Materials
Method
Results

Conclusion