Passive Processes: Diffusion

Vocabulary flashcards covering key terms related to passive diffusion, its mechanisms, and physiological relevance.

Diffusion

Passive movement of molecules from an area of higher concentration to an area of lower concentration due to their kinetic energy.

Passive Transport

Movement of substances across membranes without energy expenditure by the cell; diffusion is a prime example.

Concentration Gradient

Difference in solute concentration between two regions that drives diffusion toward the region of lower concentration.

Kinetic Energy (in diffusion)

Inherent molecular energy that causes random motion and powers diffusion without cellular energy input.

Equilibrium (in diffusion)

State in which molecules are uniformly distributed and move in all directions at equal frequency, so net diffusion ceases.

Absorption (physiological)

Process where substances enter body fluids or cells, often facilitated by diffusion across membranes.

Excretion

Removal of waste substances from the body; diffusion contributes by transporting wastes out of cells into body fluids for elimination.

Gas Exchange

Diffusion-driven movement of O₂ and CO₂ between bloodstream and tissues.

Molecular Weight (effect on diffusion)

Characteristic of a molecule that inversely affects its diffusion rate; heavier molecules generally diffuse more slowly.

Agar Gel (experimental medium)

Semisolid matrix used in labs to visualize and measure diffusion rates of dyes or other solutes.

Osmosis

The diffusion of water molecules across a selectively permeable membrane

Solution

Comprised of a solute dissolved in a solvent

Tonicity

Fluid with the higher solute concentration

Osmotic pressure

When water crosses a membrane by osmosis and enters a compartment

Hydrostatic pressure

The force of the fluid column that pushes water out of the tube through the membrane

What is Active Transport?

The movement of molecules across a cell membrane against their concentration gradient, from a region of lower concentration to a region of higher concentration, a process that requires energy.

Vesicular Transport

Vesicular transport is a general term for the movement of substances into or out of cells by vesicles. It involves the formation of membrane-bound sacs (vesicles) that enclose the substances to be transported. This process is crucial for transporting large molecules, particles, or even entire cells, which cannot pass through the plasma membrane via protein channels or transporters.

Pinocytosis

Pinocytosis is a process by which cells take in liquids or small particles from outside the cell by engulfing them in a small pocket, forming a vesicle. It's often called "cell drinking."