Biology Topic
Active Transport
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Study focus - 3 things
- Active transport moves substances from low concentration to high concentration
- It requires energy from respiration
- Root hair cells use active transport to absorb mineral ions from soil
Section 1What active transport is
Active transport is the movement of substances across a cell membrane from low concentration to high concentration. This is against the concentration gradient. Because it goes against the natural direction, the cell must use energy.
Section 2Why energy is needed
Diffusion and osmosis move down a gradient, so they do not need energy. Active transport moves up a gradient, so it needs energy released by respiration. This energy helps carrier proteins move substances across the membrane.
Section 3Example in plants
Root hair cells often absorb mineral ions from soil even when the concentration of minerals is lower in the soil than inside the root. Active transport allows the plant to take in important ions such as nitrates. These ions help the plant make proteins and grow.
Examples
A root hair cell takes nitrate ions from soil where nitrate concentration is low. Which process is being used?
Active transport is being used because the ions move from low concentration in the soil to higher concentration inside the root cell.
A cell uses energy to move mineral ions from a dilute solution into a more concentrated solution inside the cell. Why is this not diffusion?
Diffusion moves down a concentration gradient without energy. This movement is low to high concentration and uses energy, so it is active transport.
Now let's water it
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