Active Transport Against the Gradient
A cell can move substances from a low concentration to a high one by spending energy released in respiration. Covers mineral ion uptake by root hairs and glucose absorption from the small intestine.
What a learner can do afterwards
- States the direction of movement that separates active transport from diffusion and osmosis.
- Links the number of mitochondria in a cell to how much active transport it does.
- Explains why a root that cannot respire stops taking up minerals even though the water keeps coming in.
1 · Read
After PE Priya breathes fast because her muscles need energy from respiration to keep working. Diffusion and osmosis run downhill, from crowded to spread out, and cost nothing. Active transport runs uphill, from a low concentration to a high one, and the cell pays for the climb with ATP from respiration.
Root hairs sip mineral ions from poor soil where ions are scarce. The ions move into the root against the gradient, paid for by ATP. Water still enters the same root by osmosis, which costs no energy at all.
Cells that pump hard carry extra power stations. Root hair cells and gut lining cells are packed with mitochondria because they move so much stuff uphill. The sodium potassium pump spends ATP to push sodium out and pull potassium in, and nerves use it to reset after each signal.
To test whether a movement is active, cut the energy supply. If the movement stops while diffusion and osmosis carry on, it was active transport. A root that cannot respire stops taking up minerals, but water keeps coming in.
Active transport spends ATP to move substances uphill, and it stops when respiration stops.
The rewritten readings were written for this dataset.
More to read
Moving substances against a gradient
Active transport uses energy to move substances from a lower concentration to a higher one. Some pumps use ATP from respiration; cells needing much ATP often have many mitochondria. Root hairs can absorb scarce mineral ions this way. Gut cells take up glucose using an ion gradient maintained by ATP-powered pumps. Without respiration, energy-dependent mineral uptake falls. Osmosis needs no direct energy input, so water may still enter if water potential is lower inside the cell.
Transport without direct energy use
Diffusion's net movement follows concentration gradients from higher to lower concentration. Osmosis moves water through selectively permeable membranes toward lower water potential. In lungs, oxygen diffuses into the blood and carbon dioxide diffuses from the blood into the air sacs. These processes need no direct cellular energy input. Active transport requires energy to oppose a gradient. Check direction and energy use.
Membrane structures and transport
The membrane's double lipid layer restricts movement across it. Proteins provide selective routes. Channels allow passive transport; some carrier proteins use ATP to move substances against gradients. Receptors receive signals that can alter transport. Sketch a membrane with transport proteins and mark the gradients.
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Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.