Osmosis and Diffusion

Transport Across the Cell Membrane

The process of regulating the concentration of substances inside a cell.

Selective Permeability

The membrane's property that allows only certain substances to pass through.

Passive Transport

Movement of substances across the membrane without the expenditure of cellular energy.

Active Transport

Movement of substances across the membrane using energy from adenosine triphosphate (ATP).

Concentration Gradient

The difference in concentration of a substance across a space.

Diffusion

Movement of particles from an area of higher concentration to an area of lower concentration.

Isotonic Solution

Two solutions that have the same concentration of solutes.

Hypertonic Solution

A solution that has a higher concentration of solutes than another solution.

Hypotonic Solution

A solution that has a lower concentration of solutes than another solution.

Osmosis

Diffusion of water through a semipermeable membrane.

Facilitated Diffusion

Diffusion process for substances that cannot cross the lipid bilayer, using protein channels.

Filtration

Passive transport that uses a hydrostatic pressure gradient to move fluids and solutes.

Diffusion of Oxygen (O₂)

Generally, O₂ diffuses into cells where it is less concentrated.

Diffusion of Carbon Dioxide (CO₂)

Typically diffuses out of cells where its concentration is higher.

Glucose Transporter

Specialized carrier protein that transfers glucose molecules into the cell.

Sodium Channels

Membrane proteins that facilitate the diffusion of sodium ions (Na⁺) across the cell membrane.