Online Lab - Virtual Membrane Potentials

What effect does reducing the concentration of KCl in the ECF have on ion movement across the membrane?

It creates a concentration gradient for K+ and Cl- to move across the membrane.

What happens to K+ ions when a concentration gradient is established?

K+ ions flow out of the cell, resulting in a more negative charge inside.

How do ions typically move across membranes?

Ions move by diffusion from areas of high concentration to low concentration.

How much movement of ions is required to generate a membrane potential of ± 100 mV?

Only a small amount of ions need to move.

Under most conditions, how do the concentrations of ions change?

The concentrations of ions don’t significantly change.

What generates a negative membrane potential?

The combination of membrane permeability for K+ and a transmembrane KCl concentration gradient.

What happens to the membrane potential as the concentration gradient becomes larger?

The membrane potential increases.

What must happen for ions to reach electrochemical equilibrium across membranes?

Ions will flow across the membrane until they reach electrochemical equilibrium.

According to the law of electrical force, how do charges behave?

Opposite charges attract while like charges repel.

What is the Nernst potential?

It is the equilibrium membrane potential where chemical and electrical forces are equal for a selective ion.

What occurs when there is a concentration gradient and a membrane selectively permeable for an ion?

A membrane potential is generated.

How can cells change their membrane potential?

By changing the membrane selectivity through opening and closing specific ion-selective channels.

What does the Goldman-Hodgkin-Katz (GHK) equation help quantify?

It quantifies relative membrane permeability or predicts a membrane potential when multiple ions pass across the membrane.

What is the condition of the membrane potential during rest regarding K+ equilibrium?

At rest, the membrane potential does not equal the K+ equilibrium potential, and K+ is not at equilibrium.

What balances the K+ efflux at steady state?

The K+ efflux is exactly balanced by Na+ influx.

What is the relative permeability and electrochemical force for K+ and Na+ during the resting state?

There is high permeability for K+ but small electrochemical force for efflux; and low permeability for Na+ but high electrochemical driving force for Na+ influx.