The electrochemical gradient across a cell membrane typically favors the influx of sodium ions into the cell

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Reiterating the claim: The electrochemical gradient across a cell membrane typically favors the influx of sodium ions into the cell.

To evaluate this, consider two components of the gradient for Na+: the chemical (concentration) gradient and the electrical (voltage) gradient.

1) Chemical gradient: In most animal cells, extracellular Na+ concentration is higher than intracellular Na+. This difference creates a driving force for Na+ to move into the cell if the membrane becomes permeable to Na+.

2) Electrical gradient: The resting membrane potential is typically negative inside relative to the outside (often around -70 mV). Because Na+ is positively charged, the negative interior will attract Na+, producing an inward electrical current when Na+ channels open.

When both the chemical and electrical gradients align to push Na+ into the cell, the electrochemical gradient strongly favors Na+ influx. This is also consistent with the role of voltage-gated Na+ channels in action potentials, where opening of these channels results in rapid Na+ entry.

Therefore, the statement that the electrochemical gradient typically favors Na+ influx is correct.

If one were to consider exceptions, factors like altered ion concentrations, membrane potential, or conditions where Na+ channels are closed would reduce or negate influx, but under typical physiological conditions, the gradient indeed favors inward Na+ movement.

2261 BIOSC 1500 SEC1030 Cell Bio 1500'25 first midterm, 75 min version

The electrochemical gradient across a cell membrane typically favors the influx of sodium ions into the cell

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