1. Cell membrane surrounds the substance. 2. Membrane folds inward, engulfing the substance. 3. A vesicle forms, containing the substance inside the cell.

1. A vesicle containing substances moves towards the cell membrane. 2. The vesicle fuses with the cell membrane. 3. The substances are released outside the cell.

1. Pump binds intracellular sodium. 2. ATP phosphorylates the pump. 3. Pump changes conformation and releases sodium outside. 4. Pump binds extracellular potassium. 5. Pump dephosphorylates. 6. Pump returns to original conformation, releasing potassium inside.

It allows the cell to control what enters and exits, maintaining the proper internal environment.

Disrupts the electrochemical gradient, affecting nerve cell function and other cellular processes.

A flexible barrier that controls what enters and exits the cell.

A double layer of phospholipids that forms the basic structure of the cell membrane.

Proteins that span the entire cell membrane.

Proteins that sit on the surface of the cell membrane.

Movement of substances across a cell membrane against their concentration gradient, requiring energy (ATP).

Movement of substances across a cell membrane down their concentration gradient, without requiring energy.

The process by which cells engulf substances by inward folding of the cell membrane.

The process by which cells expel substances by fusion of vesicles with the cell membrane.

Active transport that uses ATP directly.

Active transport that uses the energy of an existing concentration gradient.