Passive Transport

Passive Transport

The movement of substances across the membrane without the expenditure of cellular energy.

Active Transport

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

Concentration Gradient

The difference in concentration of a substance across a space that determines the direction of diffusion.

Diffusion

The movement of particles from regions of higher concentration to areas of lower concentration.

Simple Diffusion

A natural process where molecules move from higher concentration to lower concentration without energy input.

Facilitated Diffusion

The passive transport of specific molecules across a cell membrane with the help of protein channels or carrier proteins.

Osmosis

The diffusion of water molecules from the region of higher water concentration to that of lower water concentration through a semipermeable membrane.

Selectively Permeable Membrane

A membrane that allows only certain substances to pass through while blocking others.

Channel Proteins

Transmembrane proteins that provide aqueous channels for polar substances to cross the membrane.

Carrier Proteins

Membrane proteins that bind specific substances and change shape to transport them across the membrane.

Hydrophilic

Having an affinity for water; substances that can dissolve in water.

Hydrophobic

Having an aversion to water; substances that do not dissolve in water easily.

ATP

Adenosine Triphosphate, the primary energy carrier in cells.

Hypertonic Solution

A solution with a higher concentration of solutes compared to another solution, leading to cell shrinkage.

Hypotonic Solution

A solution with a lower concentration of solutes compared to another solution, causing cell swelling.

Isotonic Solution

A solution with equal concentrations of solutes inside and outside the cell, maintaining cell size.

Endocytosis

The process by which cells take in substances from outside by engulfing them in a vesicle.

Exocytosis

The process by which cells expel substances to the outside by fusing a vesicle with the plasma membrane.

Pinocytosis

A type of endocytosis in which the cell takes in small amounts of extracellular fluid containing solutes.

Phagocytosis

A type of endocytosis in which the cell engulfs large particles or cells.

Receptor-Mediated Endocytosis

A targeted process where specific molecules bind to receptors in the plasma membrane, triggering vesicle formation and entry into the cell.

Contractile Vacuole

A specialized vacuole in some cells that pumps out excess water.

Turgor Pressure

The pressure exerted by water inside a plant cell against the cell wall.

Plasmolysis

The contraction of the protoplast of a plant cell as a result of loss of water from the cell.

Aquaporins

Channel proteins in the cell membrane that facilitate the movement of water.

Electrochemical Gradient

The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across a membrane and the ion's tendency to move relative to the membrane potential.

Cotransport

The transport of one substance across a cell membrane, coupled with the simultaneous transport of another substance across the same membrane.

Membrane Potential

The difference in electric potential between the interior and exterior of a biological cell.