bio 3: Membrane Potential & Electrical Charges

Electrical charge

Property of particles that makes them attract or repel each other.

Like charges

Repel each other.

Opposite charges

Attract each other

Positive ion (cation)

An atom or molecule that has lost electrons

Negative ion (anion)

An atom or molecule that has gained electrons.

Membrane potential

Difference in electrical charge across a cell membrane

Voltage

Measurement of the difference in electrical potential between two areas.

Inner membrane surface

Usually more negative than the outer surface.

Outer membrane surface

Usually more positive relative to the inner surface.

Why does membrane potential exist?

Unequal distribution of charged ions across the membrane.

Purpose of membrane potential

Helps power cellular processes, including nerve impulses and muscle contractions.

Ion

An atom or molecule with an electrical charge.

Sodium (Na⁺)

More concentrated outside the cell.

Potassium (K⁺)

More concentrated inside the cell.

Sodium-potassium pump

Uses ATP to move 3 Na⁺ out and 2 K⁺ into the cell.

How is membrane potential maintained?

Ion concentration gradients, selective membrane permeability, and the sodium-potassium pump.

Electrochemical gradient

Combined effect of a concentration gradient and an electrical gradient.

Resting membrane potential

Electrical charge difference across a cell membrane when the cell is not actively signaling.