AP Biology Flashcards: Tonicity and Osmoregulation
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
Why are osmoregulatory mechanisms vital for an organism's survival?
Osmoregulatory mechanisms contribute to health and survival by maintaining an organism's internal water balance and solute concentrations.
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Why are osmoregulatory mechanisms vital for an organism's survival?
Osmoregulatory mechanisms contribute to health and survival by maintaining an organism's internal water balance and solute concentrations.
Describe a hypotonic environment relative to a cell.
A hypotonic environment has a lower solute concentration and a higher water potential relative to the cell's internal environment.
How do concentration gradients affect the movement of molecules across membranes?
Concentration gradients dictate the direction of molecular movement across membranes, which is essential for maintaining growth and homeostasis.
A cell is moved from an isotonic environment to one with a lower water potential. Which way will water move and what is this new environment called?
The new environment is hypertonic, and water will move by osmosis from inside the cell to the external environment.
What are the three types of external environments a cell can be in, relative to its internal environment?
Relative to a cell, external environments can be hypotonic, hypertonic, or isotonic.
What is the relationship between the constant movement of molecules across membranes and homeostasis?
The constant movement of molecules across membranes is an essential process for maintaining an organism's growth and internal homeostasis.
What is osmoregulation?
Osmoregulation is the process that maintains water balance and allows organisms to control their internal solute concentration and water potential.
Describe a hypertonic environment relative to a cell.
A hypertonic environment has a higher solute concentration and a lower water potential relative to the cell's internal environment.
If a cell is placed in an isotonic solution, what is the net movement of water?
In an isotonic environment, there is no net movement of water across the cell membrane because the water potential is equal inside and outside the cell.
In which direction does water move during osmosis?
Water moves by osmosis from areas of high water potential to areas of low water potential.