ARCH-B-02: Osmosis Water Potential Gradients, Active Transport & Cube SA:V Diffusion Ratios

Full 15-Q Timed Drill

Step 1 of 6 • The Core Idea

ARCH-B-02: Why the 130s Classroom Method Fails Under the 90s Clock

Standard Classroom Method (Too Slow)~130s (Blows 90s Clock)

Calculate the surface area of all

6

faces:

\text{SA} = 6 \times 2^2 = 24\text{ cm}^2

. Calculate the volume:

V = 2^3 = 8\text{ cm}^3

. Divide

\text{SA}

V

\frac{24}{8} = 3\text{ cm}^{-1}

(~110s).

The Fast ShortcutTarget: 35s (Saves 95s)

Line 1 (Cube Invariant): For any cube of side

L

\frac{\text{SA}}{V} = \frac{6L^2}{L^3} = \frac{6}{L}

.
**Line 2 (Substitute

L = 2

):**

\frac{6}{2} = 3\text{ cm}^{-1}

(20s).

Where Students Lose Time: In 17 past UAT-UK questions (7.3% of Biology), candidates lose 95s by osmosis and diffusion are passive down a gradient (0 atp); only active transport uses carrier proteins + respiratory atp. Instead, apply B2 with Maths 1 skill M3.10.

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