A self-made membrane only holds things in
- The idea
- Predict
- See it
- Why
- Check
The idea
“Once a membrane closes around molecules, you have a cell that can copy and fuel itself.”
A sphere with molecules inside already looks like a cell. It only holds them. Something inside still has to do the work.
The short version
The mistake: Once a membrane closes around molecules, you have a cell that can copy and fuel itself.
What's actually true: A membrane that self-assembles solves containment. Heredity, catalysis and energy capture each need other molecules.
- Fatty acids are amphipathic, with a hydrophilic head and a hydrophobic tail. In water they can close into bilayer spheres on their own.
- That solves containment. What's inside stays together, so a replicator and its products succeed or fail as one unit.
- Heredity needs a molecule that can be copied, likely RNA. Catalysis needs a catalyst, such as a ribozyme. Capturing light needs a pigment.
On the exam: A self-made membrane holds things in. Copying, catalysis and energy need other molecules.