: Higher temperatures damage the cell membrane (denaturing membrane proteins), making it more permeable and allowing more pigment to leak out. Controlled Variables

Answer: Elodea plants are used as a model organism to investigate photosynthesis. They produce oxygen as a byproduct of photosynthesis, which can be measured and used to estimate the rate of photosynthesis.

Factors affecting reaction rates (e.g., temperature/pH), often using catalase or amylase. Plant Tissue Investigation: Beetroot tissue permeability.

Microscopy and cell observation

Use boiled potato extract (or water instead of potato). No bubbles → confirms enzyme was denatured.

Factors that must be kept constant to ensure a fair test (e.g., the volume and concentration of starch, the volume and concentration of amylase, and the pH of the solution).

Remained blue (>120s), indicating 0 concentration.

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Q2. Calculate the rate between 0–6 min and 6–10 min.

Understanding the answers and the logic behind them is crucial for students looking to excel in future exams. This article covers a detailed review of the key topics, experimental methodologies, and the expected answers for the 2020 Cambridge (CAIE) O Level Biology practical papers. 1. Key Areas Covered in the 2020 Biology Practical Exam The 2020 exams typically focused on these key themes:

Pineapple typically showed high enzyme activity, while banana showed little to none.