O Level Biology Practical 2020 Answers Official
Higher temperatures damaged cell membranes, causing more red pigment to leak into the water. Experiment 2: Banana Browning (5090/61 Alternative) Topic: Enzyme activity and oxidation.
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later.
If you are currently preparing for upcoming practical exams, practicing past papers under strict time constraints is the most effective way to build laboratory confidence and master exam techniques.
Generate high-fidelity diagrams with calculated magnifications. Question 1: Enzyme Activity and Data Investigation
Use a to measure light absorbance or transmittance quantitatively. Fluctuating water bath temperature o level biology practical 2020 answers
Identifying controlled variables, sources of error, and suggesting robust improvements. 🔬 Question 1: Enzyme Activity & Food Tests
[ \textMagnification = \frac\textDrawn length\textActual length ] (e.g., if actual cell = 0.1 mm and drawing = 20 mm → magnification = ×200)
If you:
If the experiment required calculating the rate of reaction, the formula used was: Higher temperatures damaged cell membranes, causing more red
| Test | Reagent | Positive Observation (Expected Answer) | |------|---------|----------------------------------------| | Reducing sugar | Benedict’s solution | Blue → Brick-red/orange precipitate upon heating | | Starch | Iodine solution | Brown/yellow → Blue-black | | Protein (biuret) | Biuret test (NaOH + CuSO₄) | Blue → Lilac/violet | | Fat (lipid) | Ethanol emulsion | Clear → Milky white emulsion |
: Always link biological observations to concepts like enzyme-substrate complexes or active site denaturation if temperature or pH is involved.
You are required to record the colour of the three banana slices at 5, 10, and 20 minutes. The mark scheme is very specific about what constitutes an acceptable colour description.
Length/mass change of the tissue, or the rate of gas production (bubble count). This link or copies made by others cannot be deleted
| Skill | Expected Answer Component | | :--- | :--- | | | Independent: Distance from lamp (light intensity). Dependent: Number of O₂ bubbles per minute. | | Control | Temperature (water bath), same pondweed length, same CO₂ conc (sodium hydrogencarbonate). | | Method | Place lamp at 10 cm, count bubbles for 2 min, repeat at 20 cm, 30 cm. | | Reliability | Repeat each distance 3 times and calculate mean. | | Prediction | Rate increases as light intensity increases up to a plateau. | | Precaution | Let pondweed acclimatise for 5 min before counting. |
…then you likely scored on the 2020 practical.
Data must be recorded to the same number of decimal places (e.g., 2.0, 3.5, 4.0). Identifying Sources of Error: Common Error: Temperature fluctuation in water baths.
Show your working! Even if you get the final calculation wrong, you can still get marks for the method.
Most O Level Biology practical exams in 2020 tested these three core areas:
Paper 6 (Alternative to Practical), code , is equally revealing. This paper assessed your theoretical knowledge of practical work through a written paper.
