BI-1743
Diffusion
Biology · Secondary 4 · Hard · Diffusion
A plant root cell absorbs nitrate ions from the soil by active transport. The concentration of nitrate ions in the soil solution is 5 arbitrary units, while inside the root cell it is 20 arbitrary units. Which statement explains why active transport is needed?
- Nitrate ions move from a lower to a higher concentration, so energy is required.
- Nitrate ions move from a higher to a lower concentration, so no energy is required.
- Nitrate ions are small molecules that cannot diffuse through the membrane.
- Nitrate ions move only when there is no concentration gradient.
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