Active transport refers to a procedure, which withdraws substances from a cell against the concentration gradient. During the process, the molecules move from low concentration to a high concentration.
The mechanisms of active transport need the application of the energy of the cell, generally in the form of ATP. If a substance needs to move within the cell against its concentration gradient, that is, if the substance's concentration within the cell is more than its concentration in the extracellular fluid, then the cell must utilize energy to move the substance.
Answer:
Active process
Explanation:
Neurons constantly remove sodium ions ( Na⁺) from their cell against the concentration gradient with the help of sodium potassium pumps (Na⁺ - K⁺ pumps). Since Na⁺ are being transported out of the cell against their concentration gradient it is an active transport which requires ATP in order for sodium potassium pumps to operate. Due to this active transport, a neuron is able to maintain resting state in which they have more K⁺ & less Na⁺ inside and more Na⁺ & less K⁺ in the extracellular fluid. By doing this, Na⁺ - K⁺ pumps maintain the polarity in neurons which results in a membrane potential of -70 mV in resting state.
Here it is pertinent to mention that there are many leaky channels through which Na⁺ tend to come inside neurons and K⁺ tend to go out of neurons. Various Na⁺ channels & K⁺ channels are also present in the neurons through which Na⁺ tend to come inside neurons and K⁺ tend to go out of neurons respectively. So, in order to keep Na⁺ outside and K⁺ inside, neuron needs Na⁺ - K⁺ pump which requires energy input.
