The nitrate concentration in soil water is 0.5 mM and in a root hair cell it is 2.0 mM, yet nitrate continues to enter the cell. Which process is involved, and what would stop it?
Answer and explanation
Correct answer: D. Active transport, which would stop if respiration were inhibited
- Step 1: Nitrate moves from low to high concentration, against the gradient.
- Step 2: That needs energy from respiration, so it is active transport and inhibiting respiration would stop it.
Answer
Active transport, which would stop if respiration were inhibited.
Why not the others: Diffusion, which would stop if the soil dried out: diffusion cannot move ions against the gradient. Osmosis, which would stop if the cell wall were removed: osmosis moves water, not nitrate ions. Translocation, which would stop if the xylem were blocked: this moves sugars in phloem.
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