AP Bio

Passive Transport

Movement of molecules across a membrane without energy, from high to low concentration.

Active Transport

Movement of molecules using energy (ATP), from low to high concentration.

Facilitated Transport (Facilitated Diffusion)

Passive movement of molecules with the help of a transport protein.

Endocytosis

Cell process that brings materials into the cell by forming vesicles.

Exocytosis

Cell process that releases materials out of the cell using vesicles.

Receptor-Mediated Endocytosis

A specific type of endocytosis where receptors bind to molecules before bringing them into the cell.

Pinocytosis

'Cell drinking'; the cell takes in fluids and small molecules.

Phagocytosis

'Cell eating'; the cell engulfs large particles or microorganisms.

Tonicity

How the concentration of solutes outside a cell affects water movement.

Isotonic

Solution with equal solute concentration inside and outside the cell, leading to no net water movement.

Hypotonic

Solution with lower solute concentration outside the cell, causing water to enter the cell and lead to swelling.

Hypertonic

Solution with higher solute concentration outside the cell, causing water to leave the cell and lead to shrinking.

Osmosis

The diffusion of water across a selectively permeable membrane.

Simple Diffusion

Passive movement of small, nonpolar molecules directly across the membrane.

High Concentration

A region where many molecules or solutes are present.

Low Concentration

A region where fewer molecules or solutes are present.

Concentration Gradient

The difference in concentration across a space or membrane.

Electrogenic Pump

A transport protein that moves ions and creates a charge difference across a membrane.

ATP (Adenosine Triphosphate)

The cell’s energy currency, used to power active transport and other processes.

Transport Protein

A protein in the membrane that helps substances move across (channels, carriers, pumps).