Test your knowledge of ion diffusion across the plasma membrane by placing the correct word(s) in each sentence. Then, click and drag the sentences to arrange them in a logical paragraph order. attract ion channels negative membrane potential positive integral membrane repel electrochemical gradient concentration channel gating Ion diffusion depends on the , which is the separation ion channels of electrical charge across the plasma membrane. To begin, ions diffuse across plasma membranes by passing through formed by proteins. Thus, in determining ion flux, both the concentration difference and the membrane potential, collectively known as the , must be considered. For example, most cells have a net charge inside with respect to the outside, so there is an electrical force attracting ions into the cell. Ion diffusion also depends on the gradient that exists for that ion across the plasma membrane. Finally, ion flux across the plasma membrane can be altered by opening or closing ion channels, which is a process known as . Electrical charges of the same sign, both positive or both negative, each other, while opposite charges .