3.2 Passive vs. Active Transport

Passive transport is the movement of substances across a cell membrane without the use of energy, relying on concentration gradients.

Active transport is the movement of substances across a cell membrane using energy, often against a concentration gradient.

A hypertonic solution has a higher concentration of solutes outside the cell than inside, causing water to move out of the cell.

A hypotonic solution has a lower concentration of solutes outside the cell than inside, causing water to move into the cell.

An isotonic solution has equal concentrations of solutes inside and outside the cell, resulting in no net movement of water.

Diffusion is the process by which molecules spread from areas of high concentration to areas of low concentration.

Osmosis is the diffusion of water molecules across a selectively permeable membrane.

Endocytosis is the process by which cells take in substances by engulfing them in a membrane.

Exocytosis is the process by which cells expel substances by vesicles fusing with the cell membrane.

The sodium-potassium pump is an active transport mechanism that moves sodium ions out of the cell and potassium ions into the cell.