The membrane decides what enters a plant cell
- The idea
- Predict
- See it
- Why
- Check
The idea
“The cell wall controls what gets into a plant cell.”
The wall is the outermost layer, thick and easy to see, so it looks like the gatekeeper. Water and most dissolved molecules pass right through it.
The short version
The mistake: The cell wall controls what gets into a plant cell.
What's actually true: The cell wall is a porous mesh that gives support. The plasma membrane under it controls what enters.
- The cell wall is a mesh of cellulose fibers. Water and most dissolved molecules, even the dye, pass through its gaps. It gives shape and keeps the cell from bursting.
- The plasma membrane is selectively permeable. Small nonpolar molecules like O2 cross its lipid core. Ions and large polar molecules need a transport protein.
- A cell with a damaged membrane lets the dye in, wall or no wall.
On the exam: The wall holds the cell's shape. The membrane decides what gets in.