Membrane Transport

Passive Transport

Movement of substances across a cell membrane without the use of energy, driven by concentration gradients.

Active Transport

Movement of substances across a cell membrane using energy, usually against a concentration gradient.

Diffusion

Natural movement of particles from a high concentration to a low concentration.

Simple Diffusion

Movement of small, non-polar molecules like O2 and CO2 through the phospholipid bilayer.

Osmosis

Special form of passive transport focused on the movement of water through a selectively-permeable membrane.

Tonicity

The relative concentration of solutes in a solution compared to the cell.

Isotonic Solution

A solution that has the same solute concentration as the cell, maintaining normal cell shape.

Hypertonic Solution

A solution with a higher solute concentration than the cell, causing the cell to lose water and shrink.

Hypotonic Solution

A solution with a lower solute concentration than the cell, leading to water influx and potential cell swelling or bursting.

Facilitated Diffusion

Passive transport involving the use of membrane proteins to help larger molecules or ions cross the membrane.

Concentration Gradient

The difference in concentration of a substance across a space, driving diffusion.

Transport Proteins

Proteins that assist in the movement of molecules across the cell membrane.

Endocytosis

Process of engulfing substances into the cell by enveloping them in the membrane.

Phagocytosis

Type of endocytosis referred to as 'cell eating', where the cell engulfs large particles or cells.

Pinocytosis

Type of endocytosis referred to as 'cell drinking', where the cell ingests fluids and small particles.

Receptor-Mediated Endocytosis

Selective form of endocytosis where specific substances are ingested after binding to receptors.

Exocytosis

Process of expelling substances from the cell by vesicles fusing with the cell membrane.

Cell Membrane

Selectively permeable structure surrounding the cell, regulating substance movement in and out.

Ion Channels

Proteins embedded in cell membranes that facilitate the travel of ions in and out of cells.

Concentration Gradient

The difference in concentration of a substance that drives diffusion.

Membrane Pumps

Proteins used in active transport that move ions against their concentration gradient using ATP.

Selective Permeability

Property of cell membranes that allows them to choose which substances can pass through.

ATP

Adenosine triphosphate, the energy currency used by cells for active transport.

Homeostasis

The maintenance of a stable internal environment within an organism.

Cell Signaling

Communication between cells, often using ions, facilitated by ion diffusion.

Acidosis

A condition that can arise from excess CO2 accumulation and affects cell function.