When is osmosis at equilibrium

Cells are placed in a solution and the cells then undergo hemolysis. What can be said about the relative concentrations of solute in the cell and the solution? Describe the relative concentrations inside and outside a red blood cell when crenation occurs. A saltwater fish is placed in a freshwater tank.

What will happen to the fish? Describe the flow of water molecules to explain the outcome. What makes up the "head" region of a phospholipid? Is it hydrophobic or hydrophilic? What makes up the "tail" region of a phospholipid? Water molecules will flow from the tank water into the fish because the fish has a higher concentration of salt. If the fish absorbs too much water, it will die. Allison Soult , Ph. Department of Chemistry, University of Kentucky. Learning Outcomes Define osmosis and diffusion.

Distinguish among hypotonic, hypertonic, and isotonic solutions. Describe a semipermeable membrane. Predict behavior of blood cells in different solution types.

Describe flow of solvent molecules across a membrane. Identify the polar and nonpolar regions of a cell membrane. Explain the components present in a phospholipid.

Figure 9. If a cell is in a hypertonic solution, the solution has a lower water concentration than the cell cytosol, and water moves out of the cell until both solutions are isotonic. Cells placed in a hypotonic solution will take in water across their membranes until both the external solution and the cytosol are isotonic. Diffusion Passive transport is a way that small molecules or ions move across the cell membrane without input of energy by the cell.

The Plasma Membrane and Cytosol If the outside environment of a cell is water-based, and the inside of the cell is also mostly water, something has to make sure the cell stays intact in this environment.

The Plasma Membrane The plasma membrane see figure below is made of a double layer of special lipids, known as phospholipids. The hydrophilic "water-loving" head and two hydrophobic "water-hating" tails are shown. The phospholipids form a bilayer two layers. The middle of the bilayer is an area without water. There can be water on either side of the bilayer. There are many proteins throughout the membrane. Cytosol The inside of all cells also contain a jelly-like substance called cytosol.

Supplemental Resources The Plasma Membrane: www. Concept Review Exercises 1. What are some of the features of a semipermeable membrane? What do the prefixes hyper, hypo, and iso mean? Answers 1. A semipermeable membrane allows some substances to pass through but not others. Key Takeaways Water moves into and out of cells by osmosis. Water solvent moves from an area of lower concentration solution i.

Which one has a higher concentration? Which way will water molecules flow? Which volume will increase? Which volume will decrease? Some special properties of solutions are dependent solely on the amount of dissolved solute molecules, regardless of what that solute is; these properties are known as colligative properties.

Osmosis is defined as the net flow or movement of solvent molecules through a semipermeable membrane through which solute molecules cannot pass. If a solution consisting of both solute and solvent molecules is placed on one side of a membrane and pure solvent is placed on the other side, there is a net flow of solvent into the solution side of the membrane.

Imagine osmosis taking place in an upright U-tube. The height of the solution will continue to increase due to a net flow of solvent until the added pressure of the height will cause the flow of solution to stop. The height difference between the two sides can be be converted into pressure to find the osmotic pressure exerted on the solution by the pure solvent.

Osmotic pressure is the pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane. However, in terms of solvent flow rates, the picture displays the opposite: transfer of liquid is much faster in the case of variable volume. Moreover, the established patterns of pressure and liquid influx rates differ significantly as a function of time, so do most of the osmotic characteristics, as determined at the two regimes. The results obtained in the current investigation have allowed our deriving convincing conclusions about the distinction in the kinetics of the osmotic process under different regimes: of constant and variable solution volume.

The data generated by means of the new method are of relevance to understanding the mechanisms of self-maintaining the living cell homeostasis. Further on, in stricter quantitative terms, the interpretation of the obtained differences is much more complex and would demand additional considerations. This, however, is beyond the scope of the present investigation and is the subject of our next study.

The authors of the present paper declare that none of them has any direct or indirect financial relations with any commercial identity mentioned in the paper that might lead to a conflict of interests for any of the authors.

This study is financially supported by Project no. Minkov et al. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors. Read the winning articles. Journal overview. Special Issues.

Minkov , 1,2 Emil D. Manev, 2 Svetla V. Sazdanova, 2 and Kiril H. Academic Editor: J. Received 12 Aug Accepted 07 Oct Published 26 Dec Abstract Osmosis is essential for the living organisms. Introduction Osmosis plays a primary role in biological systems. Figure 1. Schematic of the two experimental osmotic regimes: a open cell variable volume ; b closed cell constant volume. Solvent influx [mol] as a function of osmotic pressure [bar] in the regime of variable solution volume.

Table 1. Comparison of the osmotic pressure values at variable open and constant closed volume with the theoretical estimates. Figure 3. Comparison of equilibrium osmotic pressure values, as a function of solute concentration under regimes of constant and variable solution volume. The dotted line indicates the theoretical dependence see 1. Table 2. Comparison of the kinetic characteristics of the osmotic process in aqueous sucrose solutions for the two experimental regimes of constant and variable solution volume.

Active area of the semipermeable membrane. Figure 4. Osmotic pressure versus time dependence for three different initial sucrose concentrations at the two regimes: 1 0. Figure 5. Solvent influx as a function of elapsed time dependences for the three studied solute concentrations: a constant volume regime: 1 0.

Figure 6. Solvent rates of transfer dependences as a function of elapsed time for the three solute concentrations: a constant volume regime: 1 0. References J. View at: Google Scholar H. Morse, J. Frazer, and F. View at: Google Scholar J. Frazer and R. View at: Google Scholar P. Lotz and J. View at: Google Scholar D. View at: Google Scholar V. Granik, B. Smith, S. Lee, and M. Grattoni, M. Merlo, and M. Krustev, H. Kolikov, D.

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