3.5 Passive Transport

Selectively permeable

A property of plasma membranes that allows some substances to enter or leave a cell while blocking others.

Passive transport

Transport of substances across a membrane without the expenditure of cellular energy.

Concentration gradient

A physical space in which there is a different concentration of a single substance.

Diffusion

The passive process of moving from an area of higher concentration to an area of lower concentration.

Facilitated transport

Movement of substances across a plasma membrane with the assistance of transmembrane proteins without using cellular energy.

Osmosis

The movement of free water molecules through a semipermeable membrane according to the water's concentration gradient.

Tonicity

The measure of the total amount of solutes in a solution compared to another solution.

Hypotonic

A solution with a lower concentration of solutes compared to the inside of a cell, causing water to enter the cell.

Hypertonic

A solution with a higher concentration of solutes compared to the inside of a cell, causing water to leave the cell.

Isotonic

A solution with the same osmolarity as the cell, resulting in no net movement of water into or out of the cell.