TEAS science practice explained: osmosis and net movement
Short answer: Check membrane permeability and the concentration gradient before choosing a direction. At equilibrium, molecules still move even when there is no net movement.
Start with a mechanism, not an isolated definition
For a membrane question, identify what can cross, which substance is being discussed, and where its concentration is higher. A solute gradient and water movement are related, but they are not interchangeable descriptions.
Original question: predict water movement
A membrane separates two solutions. Water can cross it, but the dissolved solute cannot. Side A has a lower concentration of the solute than side B. Assume equal pressure and temperature initially. What is the initial net movement of water?
A) From A to B · B) From B to A · C) No movement because solute cannot cross · D) Only after ATP is supplied
Show the reasoning
Answer A. Under these conditions, net water movement is toward the side with the higher concentration of nonpenetrating solute. This is osmosis. B reverses the direction. C confuses the solute with the water that can cross. D confuses passive transport with an energy-requiring process.
Transfer question: change the starting condition
The same membrane now separates solutions with equal concentrations of the same nonpenetrating solute, at equal pressure and temperature. Which statement is best?
A) All water molecules stop · B) Water moves only from A to B · C) Water moves both ways with no net movement · D) The membrane begins pumping solute
Show the reasoning
Answer C. Molecular motion continues at equilibrium. Equal opposing movement means no net movement; it does not mean that individual water molecules are still. Neither a one-way flow nor a solute pump is established by the conditions in the question.
Explain why the tempting answer fails
If you chose “no movement,” separate microscopic motion from net movement. If you chose an ATP answer, ask whether the process described moves down a gradient passively. Write the actual confusion before attempting a fresh question; repeating the answer letter does not test understanding.
Use this as focused practice
These are original single-answer practice questions, not official ATI items. This page covers one concept and is not a complete Science review. ATI also uses alternative item types; these examples do not simulate those interactions. Continue with TEAS practice and read the product scope.
Sources: OpenStax Biology 2e: Passive Transport for the mechanism; ATI: TEAS Version 7 overview for exam-format scope. Examples and explanations on this page are newly written.
Can you separate the experiment from the explanation?
Practice identifying variables, spotting a confound and choosing what the observations actually support.
Frequently asked questions
Are these official TEAS questions?
No. They are original single-answer practice examples.
Does this cover all TEAS Science topics?
No. This is focused practice on passive transport; use the ATI content outline to plan broader preparation.
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