| A | B |
|---|
| phospholipid | the biomolecule that makes up the cell membrane |
| equilibrium | a condition where the concentration of a substance is the same throughout |
| concentration gradient | the concentration of a substance varying from high to low |
| diffusion | a form of passive transport where substances move from high to low concentration |
| carrier protein | a protein in the cell membrane that helps ions or molecules move through |
| osmosis | a specialized type of diffusion involving water |
| sodium potassium pump | a channel molecule that controls the movement of sodium and potassium across the membrane |
| signal | the stimulus that causes a cell to respond |
| receptor protein | cell surface proteins that bind molecules that need to get inside the cell |
| second messenger | a chemical produced inside the cell in response to a signal |
| homeostasis | the steady state of a cell |
| lipid bilayer | the cell membrane; two layers of phospholipid that controls what enters the cell |
| passive transport | transport without the expenditure of energy |
| active transport | transport that requires ATP |
| facilitated diffusion | diffusion that involves a cell surface protein |
