Question

Which of the following would not move freely across the cytoplasmic membrane?

Answer 1

Answer:

A

Explanation:

All other  options will pass through because of the state of matter,  non polarity, ( uncharged state)and molecular  size.

However Hydrogen ion can not pass through because of its Positive charge, despite it small size  it postive charge interacts with the  hydrophobic internal layer  of the phospholipid bilayer, which prevent  it entry into the cells. It is this  structural and chemical  characteristic of phospholipid that prevent  charged ions from passing through.

Rather specific  channel proteins are used by hydrogen ions to move in and out of the cell across the plasma membrane . This enable them to avoid the barrier  of interacting with  hydrophobic  internal layer  of the phospholipid bilayer.

Answer 2

Answer:

POSITIVELY CHARGED HYDROGEN IONS can not freely move through the cytoplasmic membrane.

Explanation:

The cytoplasmic membrane serves as a protective barrier between the cell and it's immediate environment.

The selective permeability of the cell prevents the free movement of hydrogen ions into and out of the cell.

Dissolved Carbon iv oxide, oxygen, small alcohols can move through the membrane by simple diffusion, through the water channels and even the lipid bilayer of the membrane.

This is due to their small sizes and nature.

For alcohols to move, it must do so by combining with the proteins embedded in the membrane, a process calked FACILITATED DIFFUSION.

This process requires energy as it is transport against the concentration gradient.