The potential difference across a cell membrane from outside...

The potential difference across a cell membrane from outside to inside is initially at $-90 \mathrm{mV}$ (when in its resting phase). When a stimulus is applied, Na" ions are allowed to move into the cell such that the potential changes to $+20 \mathrm{mV}$ for a short amount of time. (a) If the membrane capacitance per unit area is $1 \mu \mathrm{F} / \mathrm{cm}^{2},$ how much charge moves through a membrane of area $0.05 \mathrm{cm}^{2} ?$ (b) The charge on $\mathrm{Na}^{+}$ is $+e$ How many ions move through the membrane?

The potential difference across a cell membrane from outside to inside is initially at $-90 \mathrm{mV}$ (when in its resting phase). When a stimulus is applied, Na" ions are allowed to move into the cell such that the potential changes to $+20 \mathrm{mV}$ for a short amount of time.
(a) If the membrane capacitance per unit area is $1 \mu \mathrm{F} / \mathrm{cm}^{2},$ how much charge moves through a membrane of area $0.05 \mathrm{cm}^{2} ?$ (b) The charge on $\mathrm{Na}^{+}$ is $+e$ How many ions move through the membrane?

Key Concepts

Electric Potential Difference

The electric potential difference, or voltage, is the difference in electrical potential between two points, such as the inside and outside of a cell. It drives the movement of ions across the membrane, contributing to various cellular processes including action potential generation and signal propagation.

Capacitor Charge Equation

The fundamental relationship for a capacitor is given by the equation Q = CV, where Q is the charge stored, C is the capacitance, and V is the voltage across the capacitor. This equation provides a direct way to calculate the total charge movement when there is a known change in voltage across a capacitive structure like a cell membrane.

Membrane Capacitance

Membrane capacitance is a measure of a cell membrane's ability to store electrical charge. This concept treats the cell membrane as a capacitor, where the lipid bilayer acts as an insulating layer between two conductive solutions. The capacitance per unit area is often used in calculations involving biological membranes to link the stored charge to the potential difference across the membrane.

Ionic Charge and Ion Count Calculation

Each ion carries a specific elementary charge, and the total number of ions involved in a process can be computed by dividing the total charge transferred by the charge per ion. This concept is particularly useful in biological contexts where the cumulative movement of individual ions results in significant changes in membrane potential and cellular activity.

Transcript

Please give Ace some feedback