All of the following factors contribute to a polarized membrane except

None of the above.

To determine which of the factors listed does not contribute to a polarized membrane, we need to first understand what a polarized membrane is.

A polarized membrane refers to a cell membrane that has an electrical charge difference or voltage across it. This voltage difference is generated by the separation of positive and negative charges on each side of the membrane. The factors that contribute to a polarized membrane include:

1. Ion concentration gradients: Differences in the concentration of ions, such as sodium (Na+), potassium (K+), and chloride (Cl-), across the membrane can create an imbalance of charges, promoting membrane polarization.

2. Ion channels: Membrane proteins known as ion channels allow the selective movement of ions across the membrane, which affects the distribution of charges and contributes to membrane polarization.

3. Sodium-potassium pump: The sodium-potassium (Na+/K+) pump is an active transporter that helps maintain polarization by moving sodium ions out of the cell and potassium ions into the cell, against their concentration gradients.

4. Permeability of the membrane: The permeability of the cell membrane to ions and other charged molecules can influence membrane polarization. A selectively permeable membrane allows only certain ions to pass through, contributing to the establishment of a voltage difference.

From these factors, it can be deduced that all of the given factors (ion concentration gradients, ion channels, sodium-potassium pump, and permeability of the membrane) contribute to membrane polarization. Therefore, none of the factors listed would be the correct answer to the question "All of the following factors contribute to a polarized membrane except..."