Cell BiologyWorked Example

Surface Area to Volume Ratio

Part of Cell Transport — GCSE Biology

This worked example covers Surface Area to Volume Ratio within Cell Transport for GCSE Biology. Diffusion, osmosis, active transport, factors affecting transport, surface area to volume ratio, and practical investigations It is section 12 of 18 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.

Topic position

Section 12 of 18

Practice

18 questions

Recall

20 flashcards

🧮 Surface Area to Volume Ratio

Why is this ratio important?

As organisms get larger, their surface area to volume ratio gets smaller. This creates problems:

Less surface area per unit volume for exchange
Inner cells become too far from the surface
Simple diffusion becomes too slow
Need for specialized exchange surfaces and transport systems

📝 Calculation Example: Cube

For a 2cm cube:

Surface area = 6 × side² = 6 × 4 = 24 cm²
Volume = side³ = 2³ = 8 cm³
Ratio = 24:8 = 3:1

For a 4cm cube:

Surface area = 6 × 16 = 96 cm²
Volume = 64 cm³
Ratio = 96:64 = 1.5:1

Notice: Larger cube has smaller ratio!

Practice Questions for Cell Transport

Which statement best describes diffusion?

A. The movement of particles from a region of low concentration to high concentration
B. The net movement of particles from a region of high concentration to low concentration
C. The movement of water molecules through a partially permeable membrane
D. The movement of particles using energy from respiration

1 markfoundation

Explain how osmosis causes a plant cell to become plasmolysed when placed in a concentrated sugar solution.

3 marksstandard

Quick Recall Flashcards

Define diffusion

The movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. No energy is required (passive process).

Define osmosis

The movement of water molecules from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration) through a semi-permeable membrane.