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Movement of substances into and out of cells

Movement of substances into and out of cells

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Question 2

A student investigated the effect of cell size on the rate of diffusion.

They cut three different-sized cubes from a block of pink alkaline agar jelly containing phenolphthalein:

  • Cube X was 3 cm×3 cm×3 cm3\text{ cm} \times 3\text{ cm} \times 3\text{ cm}3 cm×3 cm×3 cm
  • Cube Y was 2 cm×2 cm×2 cm2\text{ cm} \times 2\text{ cm} \times 2\text{ cm}2 cm×2 cm×2 cm
  • Cube Z was 1 cm×1 cm×1 cm1\text{ cm} \times 1\text{ cm} \times 1\text{ cm}1 cm×1 cm×1 cm

The student wore safety glasses and placed the cubes into a beaker containing dilute hydrochloric acid for 10 minutes. The acid diffuses into the cubes, neutralizing the alkali and turning the agar from pink to colorless.

a.

Why did the student wear safety glasses?

[1]
b.

Explain how the acid particles entered the agar jelly.

[2]
c.

Calculate the surface area of Cube X. State the unit.

[2]
d.

Calculate the volume of Cube X. State the unit.

[2]
e.

Calculate the surface area to volume (SA:V\text{SA}:\text{V}SA:V) ratio for both Cube X and Cube Z. State which cube has the larger ratio.

[3]
f.

After 10 minutes, the acid has diffused a distance of 0.5 cm into each cube from all sides. Explain which cube has the greatest proportion of its volume turned colorless. Use this to explain why large multicellular organisms require specialized transport systems.

[4]
Markscheme

Movement of substances into and out of cells Questions

  1. IGCSE
  2. /Biology
  3. /Movement of substances into and out of cells

23 exam-style questions on Edexcel IGCSE Biology Movement of substances into and out of cells. Each one has a worked solution and a mark scheme showing where the marks go.

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