What is it?
Science Eureka is a sabbatical available in Hwa Chong Institution during the sabbatical week. It allows students to carry out experiments with guided steps and explanations. The experiments include investigating the effect of pH on the enzymatic activities of invertase.
Day 1
Experiment 1: Invertase
Objective:
To investigate the effect of pH on the enzymatic activities of invertase.
Steps:
1. 2/3 of one beaker with water and heat it over hotplates
2. Add 2ml of different test tubes
3. Add 2ml of different sucrose solutions (pH 1, pH 5.5, pH 8) into different test tubes
4. To each test tube, add 2ml of Benedict's solution
5. Boil the test tubes over a water bath for 3-5 minutes
Observations:
The sucrose solution with pH 1 turned light orange, the sucrose solution with pH 5.5 turned dark orange and the sucrose solution with pH 8 turned blue.
Explanation:
Invertase is used to catalyze the breakdown of sucrose into frustose and glucose, and it has an optimum pH of 4.5. Thus, it works best in slightly acidic conditions and will denature in pH values that are too alkali.
Invertase works better in acidic conditions, pH 8 is an alkaline, pH 1 is an acid, so invertase changes colour due to different acidic levels.
Conclusion:
Invertase works better in acidic conditions.
For more information on invertase, I went on in search for more information and found this website:
Definitions: Catalyze - to reduce the energy to start the chemical reaction
Takeaways:
1. Learnt the properties of invertase
2. Industrial uses of invertase
Experiment 2
Objective:
To determine the effect of temperature on the enzyme trypsin.
Steps:
1. Label test tubes "Hot", "Cold", "Optimum" and "Control"
2. Add 2 ml of tryspin solution into the "Hot", "Cold" and "Optimum" test tubes
3. Add 2 ml of water and 1 ml of milk into the Control test tube
4. Put some ice cubes in a beaker and add 1 ml of milk into the test tube. Wait 10 minutes and note the change in the milk.
5. Place the Hot test tube in a boiling water bath for 5 mins. Then add 5 ml of milk into the test tube, wait for 10 mins and note any change in milk.
6. Place the Optimum test tube in a water bath of 37 degrees Celsius at the side of the lab. note any change in the milk 10 min later.
(Important note: Add milk only after putting test tubes into water. Reason: To ensure that the enzymes do not digest before they are immersed in the water.)
Observations:
Milk in the Hot test tube: no change
Milk in the Cold test tube: no change
Milk in the Control test tube: no change
Milk in the Optimum test tube: clearer
Conclusion:
Enzymes work well at the optimum temperature of 37 degrees Celsius.
Explanation:
The optimum temperature of tryspin is 37 degrees Celsius. Hence, any temperature higher than 37 degrees Celsius will denature it. When the tryspin is denatured, it loses it shape and its active site is distorted, which means that it can no longer bind to the substrates to form enzyme-substrate complexes. Hence, no reaction takes place. If the temperature is lowered, the kinetic energy of the enzymes and substrate complexes will decrease. This will lead to a decrease in the frequency of successful collisions between the enzymes and substrates to form enzyme-substrate complexes, and thus the rate of reaction will be slower.
Takeaways:
2. Learnt how enzymes work
Experiment 3
Objective:
To find out how vitamin E inhibits the oxidation of phospholipids and glycolipid molecules in cell membranes possibly preventing the ageing of cells.
Steps:
1. Label the three Petri dishes- “Air”, “Oil”, and “Vitamin E”
2. Coat the surface of anthe apple slice with vitamin E and place it in the Petri dish labeled “Vitamin E”
3. Coat the surface of another apple slice with mineral oil and place it in the dish labeled “Oil”.
4. The untouched apple slice is placed in the dish labeled “Air”
5. Make observations after about 15 min, compare the 3 apple slices and note the brownness of each.
Observations;
Rank of the brownness of the apple slices in increasing manner: “Air”, “Oil”, “Vitamin E”.
Explanation:
Cells age due to the oxidation of phospholipids and glycolipid molecules in the membrane. Oxidation is the combining with oxygen in the air. In this case, the apple turns darker when ages. This is because the apple cells contain tyrosinase. Tyrosinase is a copper-containing enzyme that catalyzes the production of melanin, a dark pigment, and other pigments from tyrosine by oxidation, as the blackening of a peeled or sliced apple exposed to air.
Takeaways:
1. This experiment has thought me about Vitamin E as an antioxidant
2. I have learnt the importance of Vitamin E
Experiment 4
Objective:
To enhance the yield of fruit juice from apple pulp
Steps:
1. Place 8 dices into 2 beakers each labeling one as pectinase and the other one as water
2. Using separate 10 ml measuring cylinders, measure 10 ml of pectinase solution and 10 ml water add them to the “pectinase” beaker
3. Add 20 ml of tap water into the “water’ beaker
4. Stir both beakers
5. Cover each beaker with cling film and incubate them at 45 degrees Celsius for 20 min
6. Label 2 100ml measuring cylinders “pectinase’ and “water”
7. Filter the contents of both beakers into the respective measuring cylinder and record the volumes
Observations:
The final volumes after 20 min for Pectinase and Water respectively are 20 ml and 18 ml.
The pectinase produced a greater volume of apple juice.
Explanation:
Pectinase increases the yield of apple juice by catalyzing the breakdown of pectin in fruits. Pectin is a substance found in the cell walls of plants and pulp fibres. The apple juice that is within the fibres are released more easily, thus giving more fruit juice.
Takeaways:
1. I learnt the properties of pectinase and about its commercial use
End of Day Reflections
On this meaningful day, I have learnt a lot of skills when handling experiments in the laboratory. I have learnt that labeling can help make experiments easier and avoid making some mistakes. I have also learnt the importance of washing some apparatus before use in a new experiment. In one of the experiments, one of the beakers was not washed properly, leading to contamination and not receiving accurate results.
