Modes of Transport and Tonicity

Flashcards covering key vocabulary related to modes of transport across the cell membrane and tonicity, based on provided lecture notes.

Plasma Membrane

A selectively permeable membrane that allows certain materials in or out of the cell while blocking harmful ones.

Passive Transport

Moves substances across the cell membrane without the use of cellular energy (ATP), often following the concentration gradient.

Diffusion

The natural tendency of molecules to spread out into available space, moving from a region of higher concentration to a region of lower concentration.

Facilitated Transport

Specific transport proteins in the plasma membrane allow molecules to pass that are not small enough to pass directly or are charged.

Osmosis

The passive transport of water across the membrane, regulating water balance in and out of the cell.

Aquaporins

Specialized proteins through which water moves during osmosis.

Active Transport

Moves molecules against their concentration gradient (from low to high concentration), requiring energy input, usually from ATP.

Vesicle-mediated transport

Processes (exocytosis and endocytosis) used by large molecules and collections of molecules to move across the cell membrane.

Exocytosis

Secretory vesicles fuse with the plasma membrane to expel materials out of the cell into the extracellular fluid.

Endocytosis

The plasma membrane folds inward to bring materials into the cell, forming vesicles that contain the substance.

Tonicity

Describes how a solution affects the water volume in cells based on its osmolarity (solute concentration), determining water movement.

Hypotonic Solution

Extracellular fluid has a lower concentration of solutes than inside the cell, causing water to move into the cell and it to swell (possibly burst).

Hypertonic Solution

Extracellular fluid has a higher concentration of solutes than inside the cell, causing water to move out of the cell and it to shrink.

Isotonic Solution

Extracellular and intracellular fluids have equal solute concentrations, resulting in no net movement of water and maintaining normal cell shape and stability.

Lysis

The bursting of cells due to excessive water intake in a hypotonic solution.

Crenation

The shrinking of animal cells when water moves out in a hypertonic solution.

Plasmolysis

The shrinking of plant cells (plasma membrane pulls away from the cell wall) when water moves out in a hypertonic solution.

ATP

Adenosine triphosphate, the primary energy source used by cells for active transport.