Biology Laboratory Tests

Topics: Sodium hydroxide, Reducing sugar, Ethanol Pages: 6 (1379 words) Published: May 2, 2013
Title: Enzymes
Aim: To investigate and explain the effect of temperature on substrate concentration of enzyme catalyst. Materials/Apparatus: Test tube, test tube racks, pipette, petri dish, hot water bath, forceps, cotton wools, knives, potatoes, distilled water, hydrogen peroxide of varying concentrations Method #1

Aim: Testing the effects of temperature on catalysed activity in potato. 1. Prepared a water bath of varying temperatures.
2. Placed a small piece of crushed potato in a clean test tube and covered it. 3. Prepared three (3) other test tubes in the same manner as in Step 2 and labelled the different temperatures (0, 20, 40, 60 80, 100) oC. 4. Placed each test tube in their respective bath and left them to stand for 5 minutes. 5. After each 5 minutes expired. Each test tube was removed and left to cool. 6. Added 2ml of hydrogen peroxide.

7. Made observations.

Temperature (oC)| Number of Bubbles| Final (Seconds)|
0 oC| 3| 3|
20 oC| Tiny Bubbles| 5|
40 oC| Tiny Singular Bubbles| 270|
60 oC| Bubbles of Small Intervals| 240|
80 oC| Very Small Bubbles| 35|
100 oC| No Apparent Reaction| -|


Method #2
Aim: Testing the effect of substrate concentration in catalysts activity using potato. 1. Grinded each potato into small pieces and added equal amounts to each test tube along with equal volumes of water. 2. Allowed the mixture of potato and water to settle then removed the water from the top. 3. Added 2ml of the mixture to a boiling tube and added a stopper. 4. Removed the stopper and 2ml of 0.5% hydrogen peroxide. 5. Counted the number bubbles that emerged from the mixture. 6. Noted the time from the start to the end of the reaction. 7. Repeated the steps using varying concentrations of hydrogen peroxide. 8. Made observations

Concentrations of H2O2| Observation| Time (s)|
0.5%| Contents of test tube bubbled for 1 minute then stopped.| 1| 3.5%| Numerous Bubble| 720|


Lab #1
Title: Food Test – Starch
Aim: To investigate which food samples contain starch by testing with iodine solution Materials/Apparatus: Flour, Onion, Carrot, Milk, Mortar, Pestle, Spotting title, Pipette, Iodine Diagram:
1. The solid samples were crushed.
2. The Crushed Solid Samples were then placed on the spotting tile. 3. 2 – 3 drops of iodine was added to each food sample. 4. Approximately 1 – 2 minutes later, observations were made. Results

Food| Colour Change| Presence of Starch| Absence of Starch| Flour| Blue – Black| | -|
Onion| Yellowish – Brown| -| |
Carrot| Blue – Black| | -|
Milk| Yellowish – Brown| -| |

After the drops of iodine were added, the change was almost immediate in the samples. 2/4 of the samples had showed an indication of starch being present as shown in the results table above. Discussion:

Starch is a carbohydrate of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by all green plants as a store of energy. Iodine is a chemical element with the symbol I and an atomic number of 53. Iodine dissolved in an aqueous solution of potassium iodide reacts with starch producing a purple black colour. Conclusion:

Lab #2
Title: Food Test – Test for reducing sugars
Aim: To determine which food sample/s contain reducing sugar by testing with Benedicts Reagent Materials/Apparatus: Carrot, White Sugar, Brown Sugar, Ripe Mango, Onion, Distilled Water, 10 Test Tubes, Test Tube Rack, Spatula, Stirring Rod, Mortar, Pestle, Test Tube Holder, Measuring Cylinder, Benedicts Reagent Diagram

1. Food samples were crushed
2. The food samples were then placed in each test tube and then labelled 3. Approximately 3cm3 of distilled water was added to each test tube 4. The solution was mixed and 2cm3 of the solution was filtered from each test tube into...
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