This worksheet collection looks at the process of osmosis in detail and we explore the applications of reverse osmosis. The series spends a good amount of time exploring diffusion through membranes and compares both active and passive transport. We will compare diffusion and osmosis, which is are just a matter of the solutions that are involved. Students will explore all types of natural movement of particles. We will take a deep dive into solution science and the nature of dissolved particles and solvents. We will also look at how this process relates and functions in animal and plant cells.
Since a solute cannot pass through the membrane, the equalization has to occur by movement of the solvent. In biological systems, the solvent is always water.
In animals, osmosis plays a role in distributing nutrients to the cells and moving waste products out of them. In plants, it plays a role in how the plants absorbs water from the soil, and how that water makes its way higher up into the plant and out to the leaves.
A cell membrane (also plasma membrane or cytoplasmic membrane) is the thin, supple layer that encloses the cells of living organisms.
Its job is to keep what is inside of the cell separate from the outside of the cell.
In a biological system like a plant or an animal, osmosis is the movement of water through a cell membrane from an area of higher concentration of water to an area where the concentration of water is lower.
Reverse osmosis has many common applications. It is a common step in the purification of drinking water, as well as in converting seawater to drinking water by removing the salt and other undesirable particles.
In passive transport, the molecules move freely. This happens in processes like diffusion and osmosis, where molecules move spontaneously from areas of higher concentration to areas of lower concentration.
In diffusion, molecules move spontaneously from a higher to a lower concentration. Diffusion usually occurs in gas molecules or between molecules of liquid and gas.
When a plant absorbs water from the soil, particles of nutrients come along for the ride, and they enter the plant through the roots as well.
The function of the kidneys is to filter waste products from the blood and move them out of the body in the form of urine. After the kidneys separate waste particles from blood molecules, they have to absorb more water so that there is enough water in the blood.
Diffusion is what happens when you spray air freshener. The particles immediate begin to move away from one another until they fill the whole room.
The two processes are similar in that both result in two solutions having equal concentrations.
When there are differing concentrations of solute on either side of a membrane, it causes osmotic pressure on the side of the membrane where the concentration is highest.
A hypotonic solution has less solute and more water. A hypotonic solution has lower osmotic pressure than another solution.
When molecules move away from each other (from an area of higher concentration to an area of lower concentration), they aren’t doing it because they are aware of their surroundings.
The same thing happens with osmosis. Think of the water molecules as being in two rooms with a doorway between them that the molecules can move through.
Dutrochet noticed the similarity of the physical and chemical processes that take place in plants and animals.
Dutrochet was one of the first people to recognize that each individual cell plays a role in how a biological system (organism) functions.
When the concentration of solute is lower outside of the cell than it is inside of the cell, the tonicity is said to be hypotonic. A hypotonic solution has lower osmotic pressure than another solution.
n an isotonic situation in the human body, the fluid inside of a cell is in equilibrium with the fluid on the outside.
What Is Osmosis?
To understand biology and chemistry, you must first understand a few basic concepts on which other, more complex theories are based. These concepts may sound familiar to you but can often take time to fully understand, and one of these concepts is osmosis.
Osmosis is the movement of a liquid or other solvent (generally water) through a semipermeable membrane. In this process, the liquid/solvent moves from an area where the solute concentration is low to an area where the solute concentration is higher.
Osmosis is a simple, but highly effective process that is happening all the time inside us and around us. It is vital process which would make it exceedingly difficult for living things to thrive without. The basic concept involves the movement of solvent molecules in a solution and a membrane (soft barrier). Osmosis is the process of balancing the number of solvent molecules across this membrane. Given enough time, the number of molecules will balance on each side of this membrane. The movement of the molecules from a high concentration to the lower concentration is called osmosis. This is how plants and human body cells take in water. When we sit in a bathtub and our fingers get wrinkled, you guessed it, osmosis is the culprit. The skin in our fingers absorbs the water and gets expanded and bloated, leading to wrinkles.
Understanding Osmosis Concepts
To completely understand how osmosis works, I need to break down a few essential concepts.
Solute vs. Solvent
A solution is made up of two parts — the solute and solvent. The solvent is the base substance, while the solute is the substance dissolved in the solvent. For example, consider a solution of sugar and water. In that solution, the sugar is dissolved in the water.
Essentially, the water is the solvent, and the sugar is the solute.
If a sugar water solution is divided in half by a semipermeable membrane that allows water to pass through it, water will move from the half where there is little sugar to an area with a lot of sugar.
A semipermeable membrane is essentially a filter. It allows only the molecules of certain substances to pass through it while others are blocked. For example, consider your skin. Your skin allows certain substances to pass through it, as you'll notice when you apply lotion to your body. Others, however, are denied entry, such as (ironically) water.
Why Osmosis Is Important
Osmosis is vital for plants and animals as follows.
Many plants can only stay upright due to osmosis. When plants are placed in a hypotonic medium (where there's more solute inside the cell than outside), they take in water. This causes plant cells to become swollen, giving the structure of the plant the support it needs to stay upright.
Once the plant can stand upright, the water in the cells creates pressure against the solution the plant has been placed in. The pressure increases until it reaches osmotic pressure.
Osmotic pressure is the pressure at which a solvent is prevented from moving into a solution with a higher solute concentration, essentially halting the process of osmosis. In plants, osmosis is stopped when plant cells cannot safely take in any more water.
In animals, including humans, osmosis is essentially the foundation of life. Many of life's fundamental processes wouldn't be possible without this process.
Some of the critical roles of osmosis in humans and other animals include:
- Transporting nutrients into and waste materials out of cell walls
- Ensuring that there's a balance between the levels of water and other intercellular fluids in the body
- Ensuring that cells remain turgid without becoming overloaded with water
- Helps the small intestine absorb water
That said, it's essential to note that osmosis acts on animal cells in a different way than it does on plant cells. Animal cells can't absorb as much water as animal cells, and they'll burst open if there's too much water intake.
So, while plant cells need hypotonic solutions to allow them to stay upright, these solutions would be too much for animal cells. Instead, animal cells need isotonic solutions — that is, solutions where the levels of the solute are the same inside the cell as they're in the solution outside the cell.
There will be no net movement of water in an isotonic solution. However, water will pass back and forth such that water levels remain equal. This movement of water allows for waste expulsion, intake of nutrients, etc., and is based on osmotic principles.
Osmosis is among the most important biological processes. Without it, plants wouldn't be able to stand upright, and neither plants nor humans would be able to absorb nutrients and excrete waste products.