Summary
Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps.
In depth
Primary active transport uses ATP directly, as with the Na+/K+ pump. Secondary active transport uses an existing gradient: the sodium-glucose cotransporter (SGLT) lets glucose enter against its gradient while sodium flows in down its gradient.
Active transport allows cells to accumulate nutrients, pump out wastes and generate the electrical gradients essential for nerve function. It is specific, saturable and sensitive to metabolic poisons.
Pumps are classified as P-type (such as Na+/K+ and Ca2+ ATPases), V-type (acidify lysosomes and vacuoles), F-type (ATP synthase, run in reverse) and ABC transporters, which move drugs and lipids out. Overexpression of ABC pumps such as P-glycoprotein lets cancer cells expel chemotherapy drugs, causing multidrug resistance.
Symporters move two solutes the same way (SGLT), and antiporters swap them (Na+/Ca2+ exchanger). In plants, proton pumps create a gradient that drives uptake of sugars and nitrate.
Frequently asked questions
What is Active Transport?
Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps.
Which area of biology covers Active Transport, and how advanced is it?
Active Transport is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Sodium-Potassium Pump, Plasma Membrane, Simple Diffusion.
Why does Active Transport matter?
Cells spend a large part of their energy budget keeping gradients, and stopping the pumps, for example with cyanide, causes cells to swell and die.
Can you give an example of Active Transport?
Intestinal cells absorb glucose by SGLT driven by the sodium gradient.
What should I learn before Active Transport?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Active Transport. Intermediate topics assume the Beginner vocabulary.
What topics are related to Active Transport?
The closest topics to Active Transport are Sodium-Potassium Pump, Plasma Membrane, Simple Diffusion, Autophagy. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Active Transport?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Active Transport. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Active Transport different from Sodium-Potassium Pump?
Active Transport: Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps. Sodium-Potassium Pump: An ATPase that moves three Na+ out and two K+ into the cell per ATP, maintaining the membrane potential. Read both side by side and note what each one explains.
How should I study Active Transport step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Sodium-Potassium Pump and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.