A molecule that blocks the ion channels lining integral proteins in the plasma membrane would interfere with

Atoms

Explanation:

The windsurfer, wind and water all the things in the surroundings are made up of matter. Matter is made up of atoms. Atoms are the smallest unit that cannot be simplified further. All solid liquids and gases are made up of atoms.  

An atom is made up of three sub particles that are known as protons electrons and neutrons. An atom typically weighs around 100 pm  (picometers)