Question

proteins do not pass through plasma membranes because
multiple choice
the membrane is made of protein.
they contain nitrogen.
they bind to the phospholipids.
they are very large molecules.
they cause emulsification.

Explanation:

Plasma membranes have a lipid - bilayer structure. Proteins are large macromolecules that cannot easily diffuse through the non - polar lipid bilayer of the plasma membrane. The other options do not accurately explain why proteins don't pass through plasma membranes. The membrane is mainly made of lipids and proteins, but that's not why proteins can't pass through. Nitrogen content has no relation to membrane passage. Binding to phospholipids doesn't prevent passage and emulsification is not relevant to membrane passage of proteins.

Answer:

D. they are very large molecules.