Question

What types of molecules are permeable to a phospholipid bilayer? Rank their properties from low permeability and high permeanility

Answer 1

The permeability of molecules through a phospholipid bilayer correlates with their size, polarity, and charge. Small, nonpolar molecules like oxygen and carbon dioxide have high permeability, while large, polar molecules, and charged ions require membrane proteins to facilitate their passage.

Step-by-step explanation:

Types of Molecules Permeable to a Phospholipid Bilayer

The phospholipid bilayer is selectively permeable, allowing certain types of molecules to pass through while restricting others. Molecules that are permeable to the phospholipid bilayer include small, nonpolar molecules, such as oxygen (O₂) and carbon dioxide (CO₂). These molecules can easily pass through the bilayer because of their nonpolar nature, which is compatible with the hydrophobic interior of the bilayer.

In contrast, electrically charged ions like Na+, Cl⁻, and large or polar molecules such as sugars and amino acids, are typically not permeable because of their hydrophilic characteristics or size. They require the assistance of membrane proteins like integral or peripheral proteins to move across the cell membrane through mechanisms such as facilitated diffusion or active transport.

To rank the properties of molecules by permeability through the bilayer:

1. High Permeability: Small, nonpolar molecules (like O₂ and CO₂)
2. Moderate Permeability: Small, polar molecules without charges (like water)
3. Low Permeability: Large, polar molecules (like glucose)
4. Very Low Permeability: Charged ions (like Na+ and Cl⁻)