The Water Goes To The Salt

You'll learnwhich way water crosses a membrane, and why it moves toward the solute.

A membrane lets water through and holds the solute back, and that one asymmetry decides whether a red blood cell shrivels or bursts and why a Paramecium bails out its own pond all day. The rule is short and almost everyone writes it backwards: water runs toward the solute, not away from it. Twelve short steps; press Next for each one.

AP BIOLOGY · 12 STEPS · 6 QUICK CHECKS · WATER MOVES, SOLUTE IS TRAPPED · HIGH Ψ → LOW Ψ · v5

water crosses · solute is trapped · the water goes to the salt

Before you start

What you're looking at

One membrane in cross-section with solute discs on both sides and water crossing it — outside above, cytosol below.

The question

If one side holds more trapped solute, which way does the water move?

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