Question

1. selective permeability (2.5) define selective permeability. how does the structure of the plasma membrane determine the permeability of various types of molecules? give examples of molecules which can and can not freely diffuse through the membrane. list the three characteristics a molecule must have in order to freely pass through a membrane.

Explanation:

Selective permeability is the property of a membrane to allow certain substances to pass through while restricting others. The plasma - membrane's structure, with its lipid bilayer and embedded proteins, determines molecule permeability. Non - polar, small, and uncharged molecules like oxygen and carbon dioxide can freely diffuse, while large, polar, or charged molecules like glucose and ions cannot. For a molecule to freely pass, it should be small, non - polar, and uncharged.

Answer:

Selective permeability is the ability of a membrane to allow some substances to cross it more easily than others. The plasma membrane's lipid bilayer is hydrophobic in the interior, which allows small, non - polar molecules to diffuse through easily. Proteins in the membrane can also facilitate the passage of specific molecules. Examples of molecules that can freely diffuse are oxygen ($O_2$) and carbon dioxide ($CO_2$), while glucose and sodium ions ($Na^+$) cannot freely diffuse. A molecule must be small, non - polar, and uncharged to freely pass through a membrane.