Final answer:
Charges move toward the area that helps in equalizing the voltage and concentration discrepancies. For positive charges, this is towards the lower voltage and lower positive charge concentration, while negative charges move towards the higher voltage and lower negative charge concentration.
Step-by-step explanation:
When voltage and concentration gradients work in the same direction, charges will move in the direction that equalizes both the electrical (voltage) and chemical (concentration) differences. If the charge is positive, it will move towards the lower voltage because that is where the electrical potential is higher, which is also where the concentration of similar positive charges is lower, as charged particles are repelled by similar charges and attracted to opposite ones. Conversely, a negative charge will move towards the higher voltage, which again is towards where its concentration is lower. Therefore, in the context provided and considering a positive ion such as sodium (Na+), both the electrochemical gradient and the concentration gradient would drive it into a cell where the interior is negatively charged and the sodium concentration is lower than outside.
For example, during nerve impulse transmission, the electrochemical gradient of Na+ promotes its diffusion into the cell due to both the concentration gradient and the electrical gradient. Similarly, in the process of chemiosmosis, protons (H+) move across a membrane down their electrochemical gradient, which includes both the concentration gradient of protons and the electrical gradient across the membrane.