What characteristics must a substance have in order to be easily transported across the cell membrane?

There are three factors that a substance must have in order to diffuse through a cell membrane.

1. A substance should have the right concentration in order to diffuse through membrane as we know that molecules can only diffuse through areas of high concentration to a lower concentration. Hence the substance should have higher concentration that the cell to diffuse through the membrane.

2. The substance should not be charged as the cell membranes do not allow charged particles to enter into the cell unless the cell has electrical potential.

3. The size of the particles matters as molecules of smaller size can easily diffuse through the cell membrane

what following? you said which of the following. but there is no be more specific.