• anonymous
what exactly is active transport i am aware that it is the movement of substances across membranes that requires an expenditure or energy. but when is it used? when does it all occur?
  • Stacey Warren - Expert
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  • jamiebookeater
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  • anonymous
1. uptake of mineral salts from the soil by the root hair cell 2. for absorption of food substances from the ileum unto the blood
  • blues
It is used whenever transport of a molecule is energetically or kinetically unfavourable: 1. Whenever a molecule has to be transported against its concentration gradient. 2. Whenever a molecule has to be transported down its concentration gradient faster than the gradient is steep enough to drive it. The classic examples are pumps in cell membranes, like the K+ pump and the Ca2+ pump. Cremesupreme is right about the other examples.

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