Which of the following best describes a process that helps a cell maintain homeostasis without requiring energy to be used?
1. Channel proteins provide a passage for molecules to cross the membrane via facilitated diffusion.
2. Membrane carrier proteins help substances enter the cell against a concentration gradient.
3. Pieces of the cell membrane for vesicles circulate around extracellular materials during endocytosis.
4.Protons are pumped out of the cell to create a voltage across the cell membrane.