The unequal charge or polarity across the neuronal cell membrane at rest is due primarily to the unequal distribution of sodium ions (Na+), potassium ions (K+), chloride ions (Cl-), and protein molecules. This difference in distribution of charged substances is due to the interaction of both passive and active forces.

The resting potential is determined by concentration gradients of ions across the membrane and by membrane permeability to each type of ion. Ions move down their gradients via channels, leading to a separation of charge that creates the resting potential.

What generates the resting membrane potential is the K+ that leaks from the inside of the cell to the outside via leak K+ channels and generates a negative charge in the inside of the membrane vs the outside. At rest, the membrane is impermeable to Na+, as all of the Na+ channels are closed.

The resting membrane potential (RMP) is due to changes in membrane permeability for potassium, sodium, calcium, and chloride, which results from the movement of these ions across it. Once the membrane is polarized, it acquires a voltage, which is the difference of potentials between intra and extracellular spaces.

During depolarization, the membrane potential rapidly shifts from negative to positive. As the sodium ions rush back into the cell, they add positive charge to the cell interior, and change the membrane potential from negative to positive.

A neuron at rest is negatively charged: the inside of a cell is approximately 70 millivolts more negative than the outside (−70 mV, note that this number varies by neuron type and by species).

[3][4] The Na+K+-ATPase pump helps to maintain osmotic equilibrium and membrane potential in cells. The sodium and potassium move against the concentration gradients. The Na+ K+-ATPase pump maintains the gradient of a higher concentration of sodium extracellularly and a higher level of potassium intracellularly.

It maintains the concentration gradients of Na+ and K+, helping to stabilize resting membrane potential. If stopped working, electrochemical grandient would equalize/disappear and actions potentials could not be generated, so the cell would stop working.

In Active transport the molecules are moved across the cell membrane, pumping the molecules against the concentration gradient using ATP (energy). In Passive transport, the molecules are moved within and across the cell membrane and thus transporting it through the concentration gradient, without using ATP (energy).

The main difference between the two is that active transport requires chemical energy in the form of ATP while passive transport requires no outside energy. The biggest similarity between the two is that they both involve the movement of chemicals through a membrane.

Similarities & Differences Between Osmosis & Diffusion Active transport is the movement of molecules against the gradient, while passive transport is the molecular movement with the gradient. Two differences exist between active vs passive transport: energy usage and concentration gradient differences.

Simple diffusion and osmosis are both forms of passive transport and require none of the cell’s ATP energy.

Osmosis. One of the best examples of passive diffusion is osmosis. Essentially, osmosis refers to the movement of a solvent (e.g. water) from an area of low solute concentration to the area of higher solute concentration through a membrane.