Final answer:
The membrane potential of a real cell is around -70 mV and is caused by the presence of negatively charged ions inside the cell. It differs from a hypothetical cell because the specific ions and concentrations can vary, leading to a different membrane potential.
Step-by-step explanation:
The membrane potential of a real cell refers to the difference in charge across the cell's plasma membrane. This potential difference is typically around -70 mV and is created by the presence of negatively charged ions inside the cell and positively charged sodium ions outside the cell. When a nerve cell is stimulated, sodium ions are allowed to pass through the membrane into the cell, resulting in a positive membrane potential and the transmission of a nerve signal.
The membrane potential of a hypothetical cell would depend on the specific conditions and ions present, but it may not match the -70 mV found in real cells. In a hypothetical scenario, different ions or concentrations could lead to a different membrane potential.