By moving through the cell membrane, substances can enter and leave the cell. Three of the most common types of movement are diffusion, osmosis, and active transport.
Through the cell membrane, active transport involves the movement of molecules from a region of lower concentration to a region of higher concentration. During respiration, particles move against the gradient of concentration.
To move substances into and out of cells, active transport methods like diffusion and osmosis can be used. Active transport allows cells to absorb ions from very dilute solutions.
Plants and active transport
The roots of plants produce long "hairs" that stick out of the soil. Millions of microscopic hairs cover each branch of a root. As a result, the plant has a large surface area for absorbing water and mineral ions from the soil.
Mineral ions are essential for plant growth. Mineral concentrations in root hair cells are usually higher than in the soil around them, so they cannot take up minerals through diffusion. So, they use active transport instead.
Through active transport, the plant can absorb minerals from a very dilute solution, against a gradient of concentration. This allows it to grow. However, active transport requires energy from respiration. In humans, active transport occurs in the gut and in the kidney tubules, for example.
Active transport in humans
In the digestive system, active transport occurs when there is a low concentration of nutrients in the gut, but a high concentration in the blood.
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