Question

The major barrier to crossing a biological membrane is the hydrophobic interior of the membrane that repels what kind of molecules?

1) Hydrophilic molecules
2) Polar molecules
3) Charged molecules
4) Hydrophobic molecules

Answer 1

The hydrophobic interior of the biological membrane repels hydrophilic, polar, and charged molecules, which require transport proteins to cross. Hydrophobic molecules, however, can pass through easily if they are small enough due to their similar water-hating nature.

Step-by-step explanation:

The major barrier to crossing a biological membrane is the hydrophobic interior of the membrane, which repels hydrophilic molecules, polar molecules, and charged molecules. However, it is the easiest for hydrophobic molecules to pass through if they are small enough because they share the same water-hating characteristic of the membrane's interior. Due to this, hydrophobic molecules like carbon dioxide (CO₂) and oxygen (O₂) can easily pass through the cell membrane.

Hydrophilic molecules, polar molecules, and charged molecules, on the other hand, are repelled by the hydrophobic interior. This includes ions and large polar molecules such as sugars and proteins. If these molecules need to cross the membrane, they often require assistance from transport proteins, such as integral proteins which span the hydrophobic interior, or peripheral proteins on the membrane surface.