A student modeled the effect of cell size on the rate of diffusion in multicellular organisms.
They prepared three cubes of different sizes from a block of alkaline agar containing the pH indicator bromothymol blue, which is blue in alkaline conditions:
- Cube A was 4 cm×4 cm×4 cm4\text{ cm} \times 4\text{ cm} \times 4\text{ cm}4 cm×4 cm×4 cm
- Cube B was 3 cm×3 cm×3 cm3\text{ cm} \times 3\text{ cm} \times 3\text{ cm}3 cm×3 cm×3 cm
- Cube C was 2 cm×2 cm×2 cm2\text{ cm} \times 2\text{ cm} \times 2\text{ cm}2 cm×2 cm×2 cm
The student wore safety glasses and nitrile gloves, and carefully placed the three cubes into a beaker containing dilute sulfuric acid. As the acid diffuses into the cubes, it neutralizes the alkaline agar, turning the bromothymol blue indicator from blue to yellow.
Why did the student wear safety glasses?
Explain how the acid particles entered the agar cubes.
Calculate the surface area of Cube A. State the unit.
Calculate the volume of Cube A. State the unit.
Calculate the surface area to volume (SA:V\text{SA}:\text{V}SA:V) ratio for both Cube A and Cube C. State which cube has the larger ratio.
After 15 minutes, the acid has diffused a distance of 1.0 cm into each cube from all outer faces. Explain which cube has the greatest proportion of its volume turned yellow. Use this to explain why large multicellular organisms require specialized transport systems.