Conditions needed for effective enzyme action
Aim: To investigate the activity of enzymes and how might the activity be effected in different conditions.
Temperature rises and change of substrate concentration may cause denaturation of the protein of enzymes. So as the temperature rises the amount of active enzyme progressively decreases, and the rate is slowed. Exposure to heat causes atoms to vibrate violently and this disrupts bonds within globular proteins.(Clegg, 2007). Moreover, at lower concentration, the rate increases in direct proportion to the substrate concentration. (Clegg, 2007)
Fresh liver (will be cut into 12 small cubes with equal size). Frozen works fine| Thin spatulas to scrape liver from mortar into test tube| 4 test tubes and stand| Fine sand|
3% hydrogen peroxide| 100mL breaker|
Mortar and pestle| 10 mL Measuring cylinder|
Bunsen burner/hot plate| Detergent|
1M Hydrochloric acid (HCL)| Ruler|
Matches| Knife |
1. Cut 12 small cubes of liver (under 1 cm), of equal size. 2. Put 3 liver cubes into a test tube half filled with water and place into a beaker of boiling water for 5 minutes. 3. Place 3 liver cubes into the mortar with a small quantity if sand then grind with the pestle to form a paste. 4. Label 4 test tubes A,B,C and D and put 5ml of 3% hydrogen peroxide into each tube, followed by 3 drops of detergent in each tube. 5. Place 3 fresh liver cubes into test tube A. observe the reaction. 6. Measure the height of the bubbles formed and record the result in table1. Record any qualitative observations in Table2. 7. Place the ground liver into test tube B and record as before. 8. Place the boiled liver cubes into test tube C and record results in both tables. 9. In tube D, add 5 drops of 1M HCl to the test tube, then add the final 3 fresh liver cubes into the test tube and record results in both tables. (Year10 Science Biochemistry, p2/5)
Variables| Units| Range| How/ manipulated|
Independent variable| Time taken for reaction to finish in different conditions| minutes| 1-3| Use stop watch for accurate measurement| Dependent variable| The height of the gas bubbles formed| Cm| 16-25| Use a 30cm ruler to calculate the height formed|
Controlled variables| Units| Possible effect(s) on results| 1.Same boiling time | 5 mins| Enzyme can be denatured more due to heat increases if excess the time, which decreases the amount of active enzyme progressive more.| 2.Amount of hydrogen peroxide and detergent in each test tube| 5ml of 3% hydrogen peroxide and 3 drops of detergent in each tube| Different amount of hydrogen peroxide and detergent can cause different rate of reaction (slower or faster) due to lower/higher concentration.| 3. The same volume of test tubes (4 test tubes)| 4 exact normal test tubes| Different volume of test tubes which cause inaccurate level of bubbles being measured.| 4. The amount of liver putting in each test tube| 3 liver cubes in each test tube| Too many or too few liver can cause different rate of reaction too, such as it may not be enough enzyme (due to less liver) to break down the toxic hydrogen peroxide into water and oxygen. |
Method for controlling variables:
Controlled variables| Method for control:|
1.Same boiling time| Use a stopwatch to calculate exact time (5 mins) to avoid time excess.| 2.Amount of hydrogen peroxide and detergent in each test tube| Use the measuring cylinder to have accurate amount of hydrogen peroxide putting in to each tube so that they are the same concentration. Totally be careful when adding detergent (3 drops only)| 3. The same volume of test tubes (5 test tubes)| Choose the exact same test tubes so that they are the same in volume.| 4. The amount of liver putting in each test tube| Use the knife to cut 12 small cubes of liver (under 1 cm), of equal size,...