What is Osmosis? Read to learn more.
Throughout the rest of this week we will be asking you to evaluate different teaching strategies for helping students get to grips with osmosis, starting with the use of animations in biology, then practical work, and finally modeling. But first, we’ll begin with a quick overview of what osmosis is.
What is Osmosis?
Here’s the definition of osmosis that you will see in most textbooks:
In biology, osmosis is the movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell’s partially permeable membrane.
A partially permeable membrane (sometimes called a selectively permeable membrane) only allows certain molecules or ions to cross it
In the diagram above, the higher concentration of water molecules to the left of the partially permeable membrane makes it likely that a large number of water molecules will collide with the membrane and pass through it.
The lower concentration of water molecules on the right-hand side of the partially permeable membrane in the diagram makes it likely that fewer water molecules will collide with the membrane and pass through it.
This means that more water molecules move from left to right on this diagram than move from right to left, and so the overall movement (net movement) is to the right. It is important, though, to stress to students that water molecules are moving in both directions.
You will often see this described as movement ‘down the concentration gradient’, meaning the water is moving from a higher concentration of water (in this case, the dilute sucrose solution), to a lower concentration of water (the concentrated sucrose solution).
If a plant cell is surrounded by a solution that contains a higher concentration of water molecules than the solution inside the cell, water will enter the cell by osmosis and the plant cell will become turgid (firm). The pressure that develops inside a plant cell when it becomes turgid is called turgor pressure. Turgid plant cells help a stem to stay upright.
If a plant cell is surrounded by a solution that contains a lower concentration of water molecules than the solution inside the plant cell, water will leave the cell by osmosis and the plant cell will become flaccid (soft). If the cells in a plant stem become flaccid the turgor pressure inside them will decrease and the stem will wilt.
If a plant cell is surrounded by a solution that contains the same concentration of water molecules as the solution inside the plant cell, there is no overall net flow of water. The movement of water molecules into and out of the cell, through the partially permeable membrane, balances out.
Transpiration Keeps the Water Moving
In plants, water enters the root cells by osmosis and moves into tubes called xylem vessels to be transported to the leaves. Water molecules inside the xylem cells are strongly attracted to each other because of hydrogen bonding (this is called cohesion). When water evaporates from the leaves (through tiny pores called stomata), more water is drawn up from the root xylem cells to replace that which has been lost. A continuous column of water is, therefore, pulled up the stem in the xylem vessels by evaporation from the leaves. This is called transpiration.
This type of diagram and explanation is fairly common in biology text books, but the movement of molecules is quite abstract and this can be a difficult to concept for students to imagine.
Have a look online for a resource which helps to explain osmosis to students, and share a link below with an explanation of why it’s helpful.
© 2019-2021 STEM Learning Limited and University of Cambridge. All rights reserved.
FAQs
Osmosis is a process where water molecules move from an area of low solute concentration to high solute concentration through a semipermeable membrane. This movement can be influenced by factors like solute size and charge.
What is osmosis answers? ›
Osmosis is the passage of water molecules across a semi-permeable membrane from a solution with a high concentration to a solution with a lower concentration. It is a generalized process in which gases also participate.
What is osmosis short question answer? ›
What is osmosis? Answer: Osmosis refers to the movement of particles from low concentration to high concentration through a semi-permeable membrane. Example: Absorption of water from the soil and swelling of raisins when placed in water are examples of osmosis that we encounter in everyday life.
What is a simple definition of osmosis? ›
In biology, osmosis is the movement of water molecules from a solution with a high concentration of water molecules to a solution with a lower concentration of water molecules, through a cell's partially permeable membrane.
What is osmosis responses? ›
osmosis, the spontaneous passage or diffusion of water or other solvents through a semipermeable membrane (one that blocks the passage of dissolved substances—i.e., solutes). The process, important in biology, was first thoroughly studied in 1877 by a German plant physiologist, Wilhelm Pfeffer.
Which best explains osmosis? ›
Osmosis is the diffusion of water molecule s across a selectively permeable membrane from an area of higher concentration to an area of lower concentration. Water moves into and out of cells by osmosis.
How to explain osmosis to a child? ›
Human red blood cells placed in fresh water expand and burst. These are examples of the effects of osmosis, the process by which water passes through a cell membrane. Osmosis is possible because of the constant state of motion that exists at the atomic and molecular levels of matter.
What is osmosis short sentence? ›
osmosis noun [U] (LIQUID)
Add to word list Add to word list. biology specialized. the process in plants and animals by which a liquid moves gradually from one part of the body or the plant to another through a membrane (= cell covering): Fluid flows back into the tiny blood vessels by osmosis.
Why is water osmosis? ›
Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely maintained by osmosis across the cell membrane between the cell interior and its relatively hypotonic environment.
What is the meaning of osmosis quizlet? ›
By definition, osmosis is the diffusion of water through a selectively permeable membrane from an area of high water potential (low solute concentration) to and area of low water potential (high solute concentration).
Final answer: Osmosis is the movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.
What is the definition of osmosis in real life? ›
Osmosis refers to the movement of one, less concentrated solvent through a semi-permeable membrane to another, more concentrated solvent. Some examples of Osmosis in everyday life are:- When you keep raisin in water and the raisin gets puffed.
What is the process known as osmosis? ›
Osmosis is the process by which water moves from area of lower solute concentration to higher solute concentration across a semi-permeable membrane. This is the same as the movement of water from a higher water concentration to a lower water concentration.
What is an example of osmosis? ›
There are many everyday examples of osmosis. You can try this one yourself: if you put a potato into pure water, it swells up over time. This is because there's a much higher concentration of starch and other solutes inside the potato's cells than in the water, so water flows into the potato cells by osmosis.
Which statement best defines osmosis? ›
The correct definition of osmosis is “ Movement of solute molecules from lower concentration to a higher concentration of solution through a semipermeable membrane”.
What triggers osmosis? ›
Osmosis is a process where water molecules move from an area of low solute concentration to high solute concentration through a semipermeable membrane. This movement can be influenced by factors like solute size and charge.
What is osmosis quizlet? ›
Osmosis is best defined as the movement of. water molecules across a membrane from an area of high water concentration to an area of lower concentration.
What can osmosis be explained as? ›
The diffusion of water or solvent through a semipermeable membrane from a solution of a lower concentration of solutes to a solution of a higher concentration of solutes, to which the membrane is relatively impermeable, is called osmosis.
What is the definition of osmosis quizizz? ›
The movement of materials across the cell membrane that requires NO ENERGY from the cell. The movement of materials through (or across) the cell membrane. The ability of the cell membrane to allow some things to pass through while preventing other things from passing through.
