3B. Passive transport

Passive Transport

The movement of molecules across a membrane without requiring energy (ATP), driven by a concentration gradient.

Active Transport

The movement of molecules against their concentration gradient (low to high concentration) using energy (ATP) and membrane proteins.

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Facilitated Diffusion

A type of passive transport where molecules move down their concentration gradient through a membrane protein, without requiring energy.

Protein Channel

A transmembrane protein that forms a pore, allowing specific molecules or ions to move across the plasma membrane via facilitated diffusion.

Carrier Protein

A membrane protein that binds to a specific molecule and undergoes a conformational change to transport it across the plasma membrane.

Conformational Change

A structural change in a protein’s shape, allowing it to perform its function, such as transporting substances across a membrane.

Concentration Gradient

The difference in the concentration of a substance between two areas, driving passive and active transport across membranes.

Kinetic Energy

The energy of motion, responsible for the random movement of molecules that drives diffusion and osmosis.

Solute

A substance that dissolves in a solvent to form a solution.

Solvent

The liquid in which a solute dissolves to form a solution.

Solution

A homogeneous mixture of a solute dissolved in a solvent.

Tonicity

The ability of a solution to affect a cell’s water movement due to differences in solute concentration.

Hypertonic

A solution with a higher solute concentration than the inside of the cell, causing water to move out by osmosis.

Hypotonic

A solution with a lower solute concentration than the inside of the cell, causing water to move in by osmosis.

Isotonic

A solution where the solute concentration is equal inside and outside the cell, resulting in no net movement of water.

Osmosis

The passive movement of water molecules across a selectively permeable membrane, from lower to higher solute concentration.

Haemolysis

The rupture of red blood cells due to excessive water intake in a hypotonic solution.

Lysis

The breaking or bursting of a cell membrane, often due to excessive water intake.

Plasmolysis

The shrinking of the cytoplasm in a plant cell due to water loss in a hypertonic solution.

Turgid

A plant cell in a hypotonic solution, swollen and firm due to water entering by osmosis.

Flaccid

A plant cell in an isotonic solution, where no net water movement occurs, making it limp.