Cell membrane
A thin skin around the cell. It controls which substances go in and out.
Last updated
Analogy
A security guard at a door who checks who may enter.
In practice
Water and oxygen pass through the membrane easily. Large molecules need help.
Practice
Flashcards
- What is the job of the cell membrane?It controls what moves into and out of the cell.
Questions people ask
Why is the cell membrane called partially permeable?
Partially permeable means it lets some substances through but blocks others. Small molecules like water, oxygen and carbon dioxide pass easily. Larger molecules cannot cross freely. This lets the cell keep useful things inside and keep harmful things out, which protects the cell's chemistry.
What is the difference between a cell membrane and a cell wall?
The membrane is a thin, flexible skin found in every cell. It controls what enters and leaves. The cell wall is a thick, stiff layer made of cellulose found outside the membrane in plant cells. The wall gives support. Almost anything can pass through it.