Osmotic pressure formula, equation, and definition

The osmotic pressure formula and its concept are critical in biology. The equation is used to calculate the pressure when two solutions with different concentrations are separated by a semipermeable membrane.

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Osmotic pressure definition in biology

Osmotic pressure is defined as the minimum pressure required to apply to a solution in order to stop the flow of solvent molecules through a semipermeable membrane.

What is osmotic pressure?

Osmotic pressure is defined as the pressure required to prevent water from diffusing through a barrier due to osmosis.

It is also defined as the measure of a solution’s proclivity to absorb a pure solvent through osmosis. It is a colligative property that is affected by the concentration of solute particles in the solution. In other words, it refers to how hard the water would have to “push” through the barrier to diffuse to the other side.

In addition, osmotic pressure is determined by solute concentration. Because water will “try harder” to diffuse into an area with a high concentration of a solute, such as salt, than in an area with a low concentration.

In reality, osmotic pressure is an extension of the natural law that all matter will become randomly distributed over time, rather than a “desire” of water to move. When the concentrations of substances in two areas differ and the areas come into contact with each other, the random motion of particles causes the substances to diffuse until the solution is uniform throughout the entire area.

Osmotic pressure is a critical factor in biology because of the difference between the intracellular environment and the extracellular environment. The changes in the extracellular environment will cause water to flow into or out of cells.

This principle has been exploited by some organisms, such as plants that use osmotic pressure to move water. However, when there is too much or too little water in the extracellular environment compared to the inside of the cell, it can endanger the health of cells and organisms.

Colloid osmotic pressure

Colloid osmotic pressure also known as oncotic pressure, is a type of blood osmotic pressure caused by proteins, most notably albumin, in the plasma (blood/liquid) of a blood vessel, which causes a pull on fluid back into the capillary. Participating colloids displace water molecules, resulting in a relative water molecule deficit, with water molecules moving back into the circulatory system via capillaries at the lower venous pressure end.

The osmotic pressure of blood has the opposing effect on both hydrostatic blood pressure and interstitial colloidal osmotic pressure pushing water and small molecules out of the blood into the interstitial spaces within the arterial end capillaries. These interacting factors govern the partitioning of extracellular water between the blood plasma and the rest of the body.

Blood colloid osmotic pressure has a significant impact on the physiological function of the circulatory system. It is thought to have a significant impact on the pressure across the glomerular filter.

Osmotic pressure formula

The following formula can be used to calculate osmotic pressure

π= iCRT

  • Where π is the osmotic pressure.
  • i is the van’t Hoff factor.
  • C is the solute’s molar concentration (the number of atoms, ions, or molecules in a solute). This is significant because the number of particles (not the volume or weight) determines how the particles interact in osmosis. The molecular weight and density of the solute will determine how much a mole (a particle measurement unit) weighs or how much volume it takes up.
  • R is the ideal gas. Although the ideal gas constant was developed to refer to gases and how they diffuse and behave, it also applies to liquids.
  • T is the temperature in degrees Kelvin.

Osmotic pressure calculator

The osmotic pressure calculator assists you in calculating the pressure required to completely stop the osmosis process.

How to calculate osmotic pressure

Question

One mole of table salt is dissolved into water with a volume of one liter. At a temperature of 27C. Determine the osmotic pressure of this solution.

Working solution on how to find osmotic pressure

The molar concentration of table salt i.e. sodium chloride in the solution is 1mol per 1litre.

So, C = 1 M

Since NaCl dissociates into two ions. So, the value of the van’t Hoff factor will be 2.

i.e. i = 2.

Temperature, T = 27 C = 27 + 273 = 300 K.

Universal Gas Constant, R will be 0.0821 atm L mol−1K−1.

Now, we can apply the osmotic pressure equation:

π=i×C×R×T
Substituting the known values in the above equation we will have,

π=2×1×0.0821×300
π=49.26atm.

Thus, the osmotic pressure of the 1 M salt solution will be 49.26 atmospheres at a temperature of 27C.

Hydrostatic pressure vs osmotic pressure

Osmotic pressure vs hydrostatic pressure shows the differences between hydrostatic and osmotic pressure. These two pressures affect liquid and the differences between hydrostatic pressure and osmotic pressure will be depicted in the chart below.

Criteria
Hydrostatic pressure
Osmotic pressure
Definition
This is the pressure exerted by gravity at any point in a non-flowing liquid.
It is known as the pressure required to prevent osmosis in a solution.
Movement of solute
In non-flowing solutions, hydrostatic pressure is observed.
Osmotic pressure is measured in solutions where solutes move.
Purity of solution
Hydrostatic pressure exists in both pure and homogeneous solutions.
Pure solutions do not have osmotic pressure.
Semi-permeable membrane
A semi-permeable membrane is not used in hydrostatic pressure.
A semi-permeable membrane is involved in osmotic pressure.
Pressure at different levels
In different levels of the same liquid, the hydrostatic pressure varies.
Because osmotic pressure is constant throughout the liquid, it is calculated using the entire system.
This table shows hydrostatic vs osmotic pressure.

The primary difference between hydrostatic and osmotic pressure is that hydrostatic pressure can be found in any type of homogeneous fluid, whereas osmotic pressure can only be found in pure solutions.

Osmotic pressure examples

  1. Wilting plants
  2. Effects of dehydration and overhydration

These two examples of osmotic pressure are explained below.

Wilting plants

Many plants use osmotic pressure to keep their stems and leaves in shape. An example of osmotic pressure in plants can be seen in potted plants if you have ever kept any. In potted plants, you are probably aware that if they are not watered regularly, they can quickly wilt. However, after just a few minutes of watering, they can perk right back up. This is because osmotic pressure causes the stems and leaves of many plants to be “inflated”. This means that the salts in the cells cause water to be drawn in through osmosis, making the cell plump and firm.

If there is insufficient water, the plant will wilt because its cells will become “deflated.” In essence, they are “hypertonic” in scientific terms, which means “the concentration of solute is too high.”

As they grow, plants can also demonstrate the power of osmotic pressure. Plants may have sprouted through asphalt, or tree roots may have grown through bricks or concrete. This, too, is enabled by osmotic pressure because as plants grow, their cells absorb more water. The slow but constant pressure of water moving through the membranes of plant cells can actually push through asphalt.

Effects of dehydration and overhydration

We have all heard about the dangers of dehydration, where lack of water can have disastrous consequences for our bodies. We may be unaware that these effects are directly related to osmotic pressure.

When our bodies are dehydrated, water can actually move out of our cells and into our blood. This can result in excessive salt and other solute concentrations in our cells, interfering with cellular function. When we drink water, it enters our bodies via our bloodstreams and is able to diffuse back into our cells via osmosis, restoring their proper function.

The inverse is also true because it is possible to die from drinking too much water. Although it is difficult to “overdose” on the water by accident. Nevertheless, in extreme cases, such as water-drinking contests, it is possible to drink so much water that too much of it diffuses into your cells. In severe cases, this can result in brain swelling. For the same reason, rapid rehydration after severe dehydration can be hazardous. It is best to rehydrate slowly because filling dehydrated cells with large amounts of water all at once can cause them to burst.

FAQs on osmotic pressure

What is the osmotic pressure equation?

The osmotic pressure equation is π= iCRT. where π= osmotic pressure, i = van holt’s constant, C= molar concentration, R= ideal gas, and T= temperature in degree kelvin.

What are the osmotic pressure units?

The units of osmotic pressure are usually in pascals (pa).

A solution that contains a lower osmotic pressure than the cytoplasm of a cell is called?

A solution that contains a lower osmotic pressure than the cytoplasm of a cell is called a hypotonic solution.

Does the blood colloid osmotic pressure mostly depend on the?

The blood colloid osmotic pressure mostly depends on the high quantities of albumin.

How does high osmotic pressure occur?

First, osmotic pressure is the pressure created by water moving across a membrane due to osmosis. Therefore, the greater the movement of water across the membrane, the higher the osmotic pressure.

What causes osmotic pressure in capillaries?

Osmotic pressure in capillaries is caused by albumin proteins which results in the pulling of water into the blood.

What is plasma colloid osmotic pressure used for?

Plasma colloid osmotic pressure (COP) is an important determinant in the appearance of edema.

Which of the following generated osmotic pressure?

Sodium chloride, glucose, and albumin are the following that generated osmotic pressure.

An animal cell that is surrounded by freshwater will burst because the osmotic pressure causes?

An animal cell that is surrounded by freshwater will burst because the osmotic pressure causes water to move into the cell.

Osmotic pressure resulting from presence of plasma proteins in blood is called?

Osmotic pressure resulting from the presence of plasma proteins in blood is called blood colloid osmotic pressure.

A solution that has an osmotic pressure less than that of red blood cells is called?

A solution that has an osmotic pressure less than that of red blood cells is called a hypotonic solution or hypotonicity.

How do we define osmotic pressure?

Osmotic pressure is defined as the minimum pressure required to prevent the inward flow of a solution’s pure solvent across a semipermeable membrane. It is also defined as the measure of a solution’s proclivity to absorb a pure solvent.

An increase in the blood osmotic pressure will stimulate the release of?

An increase in the blood osmotic pressure will stimulate the release of vasopressin (also called antidiuretic hormone [ADH]) from the posterior pituitary.

What is oncotic vs osmotic pressure?

The primary distinction between osmotic pressure and oncotic pressure (oncotic pressure vs osmotic pressure) is that osmotic pressure is the pressure required to stop the net movement of water across a permeable membrane that separates the solvent and solution. Whereas, oncotic pressure is the contribution of colloids to total osmolality.

Blood colloid osmotic pressure (bcop) in the glomerulus is generated by?

Blood colloid osmotic pressure (bcop) in the glomerulus is generated by suspended proteins in the blood.

What happens to cells that are placed in hypotonic solutions?

Cells placed in a hypotonic solution tend to lose water due to osmotic pressure.

What is the osmotic pressure constant?

The osmotic pressure r constant is also known as the ideal gas constant R is 0.08206 L atm mol-1 K-1, or other values depending on the pressure units.

The plasma protein that is the major contributor to osmotic pressure is?

The plasma protein that is the major contributor to osmotic pressure is called serum albumin

The changes in blood osmotic pressure would most affect the secretion of?

Changes in blood osmotic pressure would most affect the secretion of antidiuretic hormone, which is also known as vasopressin.

What functions to maintain osmotic pressure and pH balance?

Albumin, a protein produced in the liver functions to maintain osmotic pressures and pH balance.

What is r in osmotic pressure?

R in osmotic pressure is the ideal gas constant.

What is osmotic pressure MCAT?

According to the medical college admissions test (MCAT), osmotic pressure is the tendency of water to flow through a semi-permeable membrane.

What are the most abundant plasma proteins that also establish the osmotic pressure of the plasma?

Albumins are the most abundant plasma proteins and contribute by establishing the osmotic pressure of the plasma.

Osmotic pressure is measured in units of?

Osmotic pressure is measured in units of pascal (pa)

Glomerular colloid osmotic pressure is created by?

Glomerular colloid osmotic pressure is created by plasma proteins, namely albumin.

The cation that plays a major role in determining the osmotic pressure of the plasma is?

The cation that plays a major role in determining the osmotic pressure of the plasma is the sodium ion.

What plasma protein is most important for the blood’s colloid osmotic pressure?

Albumin is the most important protein for blood colloid osmotic pressure.

The variable that affects osmotic pressure is?

The variable that affects osmotic pressure is solute concentration.

Having equal osmotic pressure with the surrounding environment is called?

Having equal osmotic pressure with the surrounding environment is called isotonicity.

What is the relationship of osmotic pressure and the number of solute particles in a solution?

The relationship between osmotic pressure and the number of solute particles in a solution is seen in the proportionality of osmotic pressure to the molar concentration of the solute particles in the solution.

What causes colloid osmotic pressure in blood?

Blood colloid osmotic pressure is largely due to plasma proteins, namely albumin, that do not diffuse readily across the capillary membrane.

A solution with the same osmotic pressure as the blood is?

A solution with the same osmotic pressure as the blood is an isotonic solution.

What causes fluid shift from osmotic pressure?

Tonicity causes a fluid shift from osmotic pressure. For example, a hypotonic solution contains fewer particles than the bloodstream, fluid moves from extracellular spaces into cells, causing cells to swell. A hypertonic solution, on the other hand, contains more solutes.

The colloid osmotic pressure in the capillary is caused by?

The colloid osmotic pressure in the capillary is caused by proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that causes a pull on fluid back into the capillary.

What is the difference between osmosis and osmotic pressure?

Osmosis is a passive process that occurs without the use of any energy. It entails the movement of molecules from a region of higher concentration to a region of lower concentration until the concentrations on both sides of the membrane become equal.

Whereas, the pressure required to prevent water from diffusing through a membrane via osmosis is referred to as osmotic pressure. The concentration of the solute determines it. Water diffuses from the lower concentration area to the higher concentration area. When the concentrations of the substances in the two areas in contact differ, the substances diffuse until the concentrations are uniform throughout.

How do we define colloid osmotic pressure?

Colloid osmotic pressure also known as oncotic pressure is a type of osmotic pressure caused by proteins, most notably albumin, in the plasma of a blood vessel, which causes a pull on fluid back into the capillary.

At what stage is the lowest osmotic pressure and highest osmotic pressure observed in humans?

The average COP of human plasma is 25.4 mm Hg. This value decreases with age, is lower in females, and is also lower in bed rest subjects. The highest osmotic pressure is observed when water is lost faster than electrolytes.

What are the structures that protect plant and animal cells from damage resulting from osmotic pressure?

The cell walls of the plant protect the plant cell from bursting when too much water has entered the cell.

How is osmotic pressure in medicine used?

In medicine, one of the ways osmotic pressure is used is in the removal of an active drug from a pill. For example, when water is absorbed through the semi-permeable membrane by osmosis, resulting in osmotic pressure. This pressure pushes the active drug out of the pill through the drilled hole (s).

Is there anything like hydrostatic osmotic pressure?

No, there is nothing like hydrostatic osmotic pressure, only hydrostatic pressure. Therefore hydrostatic pressure is the force of the fluid volume against a membrane.

How is osmotic pressure measured?

Osmotic pressure is measured in units of pascal.

What is the definition of osmotic pressure?

Osmotic pressure is the pressure that must be applied to a pure solvent in order to prevent it from passing into a given solution via osmosis; it is frequently used to express the concentration of the solution.

What is the major contributor to plasma osmotic pressure?

The major contributor to plasma osmotic pressure is Ions and glucose.

How do you explain the effect that increasing the NaCl concentration has on osmotic pressure?

Increasing the NaCl concentration increases the osmotic pressure because the force required to oppose osmosis in the closed system increases.

What is an osmotic pressure gradient?

The osmotic gradient is the concentration difference between two solutions on either side of a semipermeable membrane, and it is used to calculate the percentage concentration of a specific particle dissolved in a solution.

A major plasma protein that maintains the blood osmotic pressure is?

A major plasma protein that maintains the blood osmotic pressure is serum albumin, a protein found in blood plasma.

How do you find the osmotic pressure of combined solution?

The osmotic pressure of combined solution is proportional to the molar concentration of the solute particles in the solution. Therefore, the greater a solution’s concentration (M) or temperature (T), the greater its osmotic pressure. So when you apply the osmotic pressure equation, you can find the pressure of combined solution.

The relationship of osmotic pressure and the number of solute particles in a solution is?

The relationship of osmotic pressure and the number of solute particles in a solution is: proportional to the molar concentration of the solute particles in the solution.

Is the net osmotic pressure equal at both the arterial and the venous ends of the capillary?

Yes, the net osmotic pressure is equal at both the arterial and the venous ends of the capillary.

How is the concentration gradient of water related to osmotic pressure?

Osmotic pressure occurs according to the concentration gradient of water across the membrane, which is inversely proportional to the concentration of solutes.

What is the difference between osmotic pressure and hydrostatic pressure?

The primary difference between hydrostatic pressure and osmotic pressure is that hydrostatic pressure can be found in any type of homogeneous fluid, whereas osmotic pressure can only be found in pure solutions.

The plasma proteins that have the greatest effect on osmotic pressure are?

The plasma proteins that have the greatest effect on osmotic pressure are albumin (21.8 mm Hg), followed by globulins (6 mm Hg), and then fibrinogen (0.2 mm Hg).

What is the van t Hoff equation of osmotic pressure?

The van’t Hoff equation of osmotic pressure is π= iCRT. where π= osmotic pressure, i = van holt’s constant, C= molar concentration, R= ideal gas, and T= temperature in degree kelvin.

What is blood osmotic pressure?

Blood colloidal osmotic pressure is the pressure created by the concentration of colloidal proteins in the blood (BCOP).

How will the osmotic pressure of an aqueous solution change as evaporation occurs?

The osmotic pressure will increase or decrease when its unit equals the vapor pressure of water.

How do you calculate the osmotic pressure?

To calculate the osmotic pressure, one must use the equation of the formula (π= iCRT).

How is blood colloid osmotic pressure produced?

Blood colloid osmotic pressure is produced by albumin.

What is the osmotic pressure of glucose?

The osmotic pressure of the glucose solution is the difference in the pressure between the two sides of the solution.

Which plasma constituent is the main contributor to osmotic pressure?

Albumin.

Which ideal solution exhibits the greatest osmotic pressure?

MgCl2 has the highest osmotic pressure because it breaks down into three ions in water, whereas the others only break down into two.

Which of the electrolyte solutes is most responsible for osmotic pressure in body fluids and cells?

The only electrolyte solutes that exert significant osmotic pressure are sodium.

How is osmotic pressure in the body maintained?

The body is constantly consuming and losing water and electrolytes. Excess electrolytes and wastes produced by osmoregulation are transported to and excreted by the kidneys. The excretion process aids the body in maintaining osmotic balance.

What is the osmotic pressure meaning?

It is the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution via osmosis, which is frequently used to express the solution’s concentration.

What is the relationship of osmotic pressure and the number of solute particles in a solution?

The relationship of osmotic pressure and the number of solute particles in a solution is the proportionality of molar concentration to osmotic pressure.

This video explains osmotic pressure.

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