Cellar Processes

Homeostasis

The maintenance of a constant state of balance by cells and organisms.

Semipermeable Membrane

A membrane that selectively allows certain substances to pass through while keeping others out.

Nonpolar Molecule

A molecule lacking chemical polarity, allowing it to freely pass across the cell membrane.

Polar Molecule

A molecule with slight positive and negative charges at different ends, unable to freely pass across the cell membrane.

Diffusion

The movement of a substance from an area of high concentration to an area of lower concentration, often passive.

Osmosis

The diffusion of water across the cell membrane.

Facilitated Diffusion

The diffusion of a polar substance with the assistance of a carrier protein, requiring no energy.

Endocytosis

The process of taking materials into the cell by forming a pocket in the cell membrane.

Exocytosis

The release of molecules from the cell by spreading them out from a region of high concentration to a region of lower concentration.

Transport Protein

A protein that aids in the movement of substances across the cell membrane, either by changing shape (carrier protein) or forming a channel (channel protein).

Passive Transport

The transport of substances across the cell membrane that does not require energy.

Active Transport

The transport of substances across the cell membrane that requires energy, typically ATP.

ATP

Adenosine triphosphate, the energy "currency" of cells.

With (down) the Concentration Gradient

Passive movement of substances along the concentration gradient (from high to low concentration).

Against (up) the Concentration Gradient

Active movement of substances against the concentration gradient (from low to high concentration), requiring energy.

Hypotonic

In the context of the cell, a solution surrounding the cell with a high solute concentration and low water concentration, causing water to move into the cell.

Hypertonic

In the context of the cell, a solution surrounding the cell with a low solute concentration and high water concentration, causing water to move out of the cell.

Isotonic

In the context of the cell, a solution surrounding the cell with the same solute concentration as the cell, resulting in no net movement of water.