* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
AP Water Potential Math Name: Introduction: Water potential is the measure of water’s potential energy or it’s ability to do work. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as capillary action (which is caused by surface tension). Water potential integrates a variety of different potential drivers of water movement, which may operate in the same or different directions. Within complex biological systems, it is common for many potential factors to be important. For example, the addition of solutes to water lowers the water's potential (makes it more negative), just as the increase in pressure increases its potential (makes it more positive). If there is no restriction on flow, water will move from an area of higher water potential to an area that has a lower water potential. Ψ = Ψ𝑠 + Ψ𝑝 Pressure potential is based on mechanical pressure, and is an important component of the total water potential within plant cells. Pressure potential increases as water enters a cell. As water passes through the cell wall and cell membrane, it increases the total amount of water present inside the cell, which exerts an outward pressure that is opposed by the structural rigidity of the cell wall. By creating this pressure, the plant can maintain turgor, which allows the plant to keep its rigidity. Without turgor, plants lose structure and wilt. The pressure potential in a living plant cell is usually positive. In plasmolysed cells, pressure potential is almost zero. Negative pressure potentials occur when water is pulled through an open system such as a plant xylem vessel. Withstanding negative pressure potentials (frequently called tension) is an important adaptation of xylem. Ψ𝑠 = −𝑖𝐶𝑅𝑇 Osmotic potential has important implications for many living organisms. If a living cell is surrounded by a more concentrated solution, the cell will tend to lose water to the more negative water potential of the surrounding environment. A soil solution also experiences osmotic potential. The osmotic potential is made possible due to the presence of both inorganic and organic solutes in the soil solution. As water molecules increasingly clump around solute ions or molecules, the freedom of movement, and thus the potential energy, of the water is lowered. As the concentration of solutes is increased, the osmotic potential of the soil solution is reduced. Since water has a tendency to move toward lower energy levels, water will want to travel toward the zone of higher solute concentrations. Osmotic potential has an extreme influence on the rate of water uptake by plants. a) addition of solutes on right side reduces water potential. S = -0.23. Water flows from hypotonic to hypertonic or from high on left to low on right. b) adding +0.23 pressure with plunger creates no net flow of water. c) applying +0.30 pressure increases water potential solution now has of +0.07. Water moves right to left d) negative pressure or tension using plunger decreases water potential on the left. Water moves from right to left Helpful Hints Remember water always moves from [high] to [low]. Water moves from hypotonic to hypertonic. [Solute] is related to osmotic pressure. Pressure is related to pressure potential. Pressure raises water potential. When working problems, use zero for pressure potential in animal cells & open beakers. 1 bar of pressure = 1 atmosphere Directions: Answer the following questions using the equations on the front page. Keep in mind that is measured in megapascals (MPa) and 1 Mpa = 10 atmospheres of pressure. 1. If a plant cell’s P = 2 bars and its S = -3.5 bars, what is the resulting ? a. The plant cell from question 1 is placed in a beaker of sugar water with S = -4.0 bars. In which direction will the net flow of water be? b. The original cell from question 1 is placed in a beaker of sugar water with S = -0.15MPa (megapascals). We know that 1 MPa = 10 bars. In which direction will the net flow of water be? 2. The value for in root tissue was found to be -3.3 bars. If you place the root tissue in a 0.1 M solution of sucrose at 20°C in an open beaker, what is the of the solution, and in which direction would the net flow of water be? a. NaCl dissociates into 2 particles in water: Na+ and Cl-. If the solution in question 2 contained 0.1 M NaCl instead of 0.1 M sucrose, what is the of the solution, and in which direction would the net flow of water be? 3. A plant cell with a s of -7.5 bars keeps a constant volume when immersed in an open-beaker solution that has a s of -4 bars. What is the cell’s P? 4. At 20°C, a plant cell containing 0.6 M glucose is in equilibrium with its surrounding solution containing 0.5 M glucose in an open container. What is the cell’s P?