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Neuron plasma membranes are most permeable to potassium ions (K+) due to the presence of leak potassium channels. This allows for the resting membrane potential to be closer to the equilibrium potential for potassium. Sodium ions (Na+) and chloride ions (Cl-) also play roles in membrane potential, but potassium ions have the highest permeability.
Small, uncharged molecules like oxygen and carbon dioxide are permeable to phospholipids in the plasma membrane, while ions such as sodium (Na+), potassium (K+), and chloride (Cl-) are not permeable due to their charge.
Cell membranes are selectively permeable, allowing certain molecules or ions to pass through while restricting the passage of others. This permeability is crucial for maintaining cellular homeostasis by controlling the movement of substances in and out of the cell. The lipid bilayer of the membrane and embedded proteins play key roles in regulating this permeability.
Na and K ions cannot easily diffuse through plasma membranes because the phospholipid bilayer is hydrophobic, creating a barrier to the movement of ions, which are hydrophilic. Additionally, the presence of ion channels and pumps in the membrane regulates the movement of Na and K ions in and out of the cell through specific mechanisms.
A permeable membrane is a barrier that allows certain substances to pass through while blocking others based on size, charge, or other properties. This selective permeability enables the membrane to regulate the flow of molecules or ions in and out of a cell or compartment. Examples of permeable membranes include cell membranes and dialysis membranes.
Gap junctions are small channels that form across the plasma membranes of adjacent cells, allowing for direct communication and exchange of ions, small molecules, and signaling molecules between the cells.