GCSE Biology Revision "Required Practical 3: Effects of Osmosis on Plant Tissue"

Summary

This educational video explains how to investigate the effect of osmosis on plant tissue, specifically using potato cylinders. It details the experimental setup, including the preparation of potato samples, the use of different sugar solutions, and the measurement of changes in mass and length. The video emphasizes the importance of calculating percentage change in mass, providing examples and the necessary formula. Finally, it illustrates how to interpret results graphically, highlighting the behavior of plant cells in various concentrations of sugar solutions, thereby enhancing understanding of osmosis in biological contexts.

Takeaways

• 😀 Osmosis is defined as the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• 😀 When plant cells are placed in water, they absorb water and swell, while in a concentrated solution, they lose water and shrink.
• 😀 Potato is commonly used to investigate osmosis, but other vegetables like beetroot and parsnip can also be used.
• 😀 To ensure uniformity, potato cylinders are cut using a cork borer and trimmed to the same length (approximately 3 cm).
• 😀 It's crucial to measure the initial length and mass of the potato cylinders before starting the osmosis experiment.
• 😀 The experiment involves placing potato cylinders in various sugar solutions (0.5 M, 0.25 M, and distilled water) to observe osmosis.
• 😀 Distilled water is preferred over tap water in experiments to avoid the influence of dissolved substances.
• 😀 After soaking overnight, potato cylinders are gently dried to remove surface moisture without pressing out internal water.
• 😀 Percentage change in mass is calculated using the formula: (Change in value / Original value) x 100.
• 😀 Graphs can be plotted to visualize the relationship between sugar solution concentration and percentage change in mass.

Q & A

What is osmosis?

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

How does osmosis affect plant cells when placed in water?

When plant cells are placed in water, water moves into the cells by osmosis, causing them to swell and become turgid.

What happens to plant cells when they are placed in a concentrated sugar solution?

In a concentrated sugar solution, water moves out of the plant cells by osmosis, leading to cell shrinkage.

Why do we peel the potato before the experiment?

The potato skin can affect osmosis, so peeling it ensures that only the potato tissue is involved in the experiment.

Why is it important to use distilled water in the experiment?

Distilled water contains no dissolved substances that could affect the weight changes observed due to osmosis.

What is the purpose of using cylinders of potato in this experiment?

Cylinders of potato provide uniform samples for measuring the effects of osmosis under controlled conditions.

What should you do after leaving the potato cylinders in the solutions overnight?

After overnight exposure, you should gently roll the potato cylinders on paper towels to remove surface moisture without forcing water out of the cells.

How do you calculate percentage change in mass?

Percentage change in mass is calculated using the formula: (Change in Value / Original Value) x 100.

What does it indicate when the graph of percentage change crosses the x-axis?

The point where the graph crosses the x-axis indicates that there is no change in mass, meaning the concentration outside the cell is equal to that inside.

Why is it important to learn the percentage change formula for the exam?

The percentage change formula is not provided in the exam, so it is essential to memorize it for calculations related to osmosis experiments.