Learners explore a situation in which molecules could potentially pass through a selectively permeable membrane.
After completing this tutorial, you will be able to complete the following:
Molecules move constantly. During this continuous movement, the molecules collide with one another and eventually spread out randomly. Diffusion, or more scientifically known as molecular diffusion, is the movement of molecules from an area of higher concentration to an area of lower concentration. After a period of time where diffusion has had time to move all molecules to equal concentrations, the system is described as reaching equilibrium. Equilibrium is when the concentration of molecules is the same throughout a system.
Diffusion across a cell membrane requires zero energy from the cell. The movement of molecules that requires no energy is termed as passive transport. Osmosis, or the movement of water molecules from an area of higher concentration to an area of lower concentration, is another type of passive transport.
Another form of diffusion which does not require energy is termed as facilitated diffusion. Facilitated diffusion uses transport proteins, or simple channels, to carry larger, more complex molecules from one side of a plasma membrane with a high concentration to the other, lower concentrated side. Facilitated diffusion, as mentioned, does not require energy and is there considered a type of passive transport, just as diffusion is.
|Approximate Time||2 Minutes|
|Pre-requisite Concepts||cellular membrane, homeostasis, solubility, solvent|
|Type of Tutorial||Experiment|
|Key Vocabulary||birth rate, competition, crowding|