Cell Transport Terms

biology

passive transport

the movement of molecules across a cell membrane without the use of energy, often down their concentration gradient (Hi to Low concentration).

simple diffusion

the process by which molecules and ions move from an area of higher concentration to an area of lower concentration, resulting in even distribution.

facilitated diffusion

a type of passive transport that allows molecules to cross membranes with the assistance of special proteins (transport proteins: carrier proteins and channel proteins), without using energy.

osmosis

the diffusion of water molecules across a selectively permeable membrane, moving from an area greater amount of water/lower solute concentration to an area of lower amount of water/higher solute concentration. Osmosis is essential for maintaining water balance in a cell. (Ex: a potato that has starch (a solute) placed in water will swell because the water is moving from an area of less solute to high solute.) 

active transport

the process of moving molecules across a cell membrane from an area of lower concentration to an area of higher concentration, requiring energy in the form of ATP (Low to High concentration).

exocytosis

the process by which a cell expels materials in vesicles that fuse with the plasma membrane, releasing their contents outside the cell.

endocytosis

the process by which a cell takes in materials by engulfing them in vesicles formed from the plasma membrane. There are 3 types: phagocytosis; pinocytosis; and receptor-mediated endocytosis.

sodium potassium pump

a membrane protein that actively transports sodium out of and potassium into the cell, crucial for maintaining cellular homeostasis and membrane potential.

phagocytosis

the process by which a cell engulfs large particles or other cells, forming a vesicle to internalize the material.

pinocytosis

the process by which a cell takes in small quantities of liquid and dissolved substances, forming vesicles to internalize the material.

receptor-mediated endocytosis

a specific form of endocytosis where cells internalize molecules by binding them to receptors on their surface, leading to vesicle formation.

equilibrium

the state in which the concentration of substances is equal across a space, resulting in no net movement of particles.

hypertonic

a solution with a higher concentration of solutes compared to another solution, causing cells to lose water and shrink.

hypotonic

a solution with a lower concentration of solutes compared to another solution, leading to water influx into cells and potential swelling.

isotonic

a solution or environment where the concentration of solutes is the same inside and outside a cell, resulting in no net movement of water across the cell membrane

vacuole

a membrane-bound organelle in plant and fungal cells that stores nutrients, waste products, and helps maintain turgor pressure.

channel protein

a type of membrane protein that facilitates the transport of specific molecules across a cell membrane, often allowing ions or polar molecules to pass through.

polar

molecules that have uneven distribution of charge, resulting in partial positive and negative ends.

nonpolar

molecules that have an even distribution of charge, resulting in no distinct positive or negative ends.

ion

an atom or molecule that carries a positive or negative charge due to the loss or gain of one or more electrons.

phospholipid bilayer

a double layer of phospholipids that makes up the cell membrane, with hydrophilic/polar heads facing outward and hydrophobic/nonpolar tails facing inward.

homeostasis

the process by which living organisms regulate their internal environment to maintain stable, constant conditions despite external changes.

aquaporins

proteins that facilitate the transport of water across cell membranes, allowing for rapid movement of water in and out of cells.

vesicle

a small membrane-bound sac that transports materials within or outside of a cell.

concentration gradient

the difference in the concentration of a substance between two regions, which drives the movement of substances across membranes.

selectively permeable membrane

a biological membrane that allows certain molecules or ions to pass through while blocking others, thereby regulating the movement of substances in and out of the cell.

carrier proteins

proteins that facilitate the transport of specific substances across a cell membrane by changing shape. They bind to molecules and undergo conformational changes to move them across. Carrier proteins are responsible for diffusion of sugars, amino acids, and nucleosides across the plasma membranes of most cells.

embedded protein

proteins embedded in the phospholipid bilayer and help with transportation of molecules in and out of the cell.