Osmosis, Diffusion, and Active Transport

Vocabulary flashcards covering passive and active transport, osmosis, diffusion, tonicity solutions, and cellular bulk transport mechanisms.

Diffusion

The random movement of particles of a solute from an area of higher concentration to an area of lower concentration, moving with (down) a concentration gradient without requiring cellular energy.

Osmosis

The diffusion of water molecules through a selectively permeable membrane from a higher concentration of water to a lower concentration of water (toward an area with a greater amount of solute).

Concentration Gradient

The difference in concentration between a region of high concentration and a region of lower concentration across a membrane.

Passive Transport

Cellular transport that does not require cell energy; examples include diffusion, facilitated diffusion, and osmosis.

Active Transport

A cellular transport process that requires energy in the form of $\text{ATP}$ to move solute particles against the concentration gradient (from low concentration to high concentration).

Equilibrium

The state when the concentrations across a membrane become equal; net diffusion stops, but molecular movement continues at an equal rate in both directions.

Factors Affecting Transport Rate

The three conditions that determine the rate of transport: 1) whether the material is a solid, liquid, or gas; 2) the size of the molecules; and 3) temperature.

Isotonic Solution

A solution in which the concentration of solute inside and outside of the cell is the same, resulting in equal water movement in and out, no net movement of water, and normal homeostasis for animal cells.

Hypotonic Solution

A solution in which the concentration of solute is lower outside the cell than inside the cell, causing water to enter the cell and increase internal pressure.

Turgor Pressure

The pressure that builds up inside plant cells when placed in a hypotonic solution as water enters, providing the plant cells with shape and support.

Cytolysis

The swelling and bursting of animal cells that occurs when placed in a hypotonic solution due to increased osmotic pressure.

Hypertonic Solution

A solution in which the concentration of solute is higher outside the cell than inside the cell, causing water to exit the cell.

Plasmolysis

The drop in turgor or osmotic pressure caused by water loss in a hypertonic solution, causing animal cells to shrivel up and plant cells to wilt as their cell body shrinks away from the cell wall.

Facilitated Diffusion

A passive transport process that moves particles down their concentration gradient using transport or channel proteins, typically for specific molecules like glucose, stopping at equilibrium.

Carrier Proteins (Protein Pumps)

Membrane-embedded proteins that change shape using energy ($\text{ATP}$) to pick up specific ions or molecules and carry them across the plasma membrane against the concentration gradient.

Endocytosis

An active transport process of taking materials into the cell by means of infoldings, or pockets, of the cell membrane, usually packaging them into a vacuole.

Phagocytosis

A type of endocytosis referred to as 'cell eating,' characterized by the intake of solid, nonspecific molecules.

Pinocytosis

A type of endocytosis referred to as 'cell drinking,' characterized by the intake of small droplets of liquid containing nonspecific molecules.

Exocytosis

A process of active transport (reverse endocytosis) in which the membrane of a vacuole surrounding material fuses with the cell membrane, forcing the contents out of the cell.