though there is already a higher concentration of mineral ions in the plant, even more can be absorbed from the soil by active transport.
2. Glucose always moves from the kidney tubules and the gut into the blood no matter what the concentration gradient- and when it moves against the gradient, it moves by active transport.
3. In animals, marine animals often take in too much salt for their kidneys to handle. To solve this problem, there are special salt glands in the body, which get rid of the salt from the animal even against the concentration gradient- by active transport. This is vital for the survival of marine animals.
MAIN POINTS TO REMEMBER:
1) SUBSTANCES CAN SOMETIMES BE ABSORBED AGAINST THE CONCENTRATION GRADIENT BY ACTIVE TRANSPORT.
2) ACTIVE TRANSPORT REQUIRES ENERGY FROM RESPIRING CELLS.
3) THROUGH ACTIVE TRANSPORT, CELLS CAN ABSORB IONS FROM VERY DILUTE SOLUTIONS AND ALSO MOVE MOLECULES THROUGH CELL MEMBRANES.
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