Why Are Cells So Small

Introduction

• Topic: Understanding why cells are small.
• Illustration Used: Three cubes of different dimensions (1mm, 2mm, 10mm) are used to explain the concept.
• Key Concept: Surface area to volume ratio.

Surface Area to Volume Ratio

• As cells grow larger, the surface area to volume ratio decreases.
• Smaller cells have a larger surface area to volume ratio.

Mathematical Explanation

Surface Area of a Cube

• Equation: Surface area of a cube = 6 (length x width)
• 1mm Cube: 6 x 1 x 1 = 6 mm²
• 2mm Cube: 6 x 2² = 24 mm²
• 10mm Cube: 6 x 10² = 600 mm²

Volume of a Cube

• Equation: Volume of a cube = length x width x height
• 1mm Cube: 1 x 1 x 1 = 1 mm³
• 2mm Cube: 2 x 2 x 2 = 8 mm³
• 10mm Cube: 10 x 10 x 10 = 1000 mm³

Calculating Surface Area to Volume Ratio

• 1mm Cube: 6/1 = 6:1
• 2mm Cube: 24/8 = 3:1
• 10mm Cube: 600/1000 = 3/5
• Conclusion: Smaller cubes have a larger surface area to volume ratio.

Practical Implications

Ice Example

• Comparison: 1-liter block of ice vs. 1-liter chipped ice.
• Melting Rate: Chipped ice melts faster due to higher surface area to volume ratio.
• Reason: Higher surface area allows faster diffusion of heat.

Application to Cells

• Nutrient and gas diffusion is easier in smaller cells.
• Larger cells face difficulty in diffusing necessary substances.

Conclusion

• Cells are small to maximize the surface area to volume ratio.
• Efficient diffusion of nutrients and gases is crucial for cell function.

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End of Lecture: Understanding the need for small cell size through mathematical and practical examples.