solute

Examples of solute in the following topics:

• Tonicity

  • A solution's tonicity often directly correlates with the osmolarity of the solution.
  • Osmolarity describes the total solute concentration of the solution.
  • A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles.
  • Therefore, a solution that is cloudy with cells may have a lower osmolarity than a solution that is clear if the second solution contains more dissolved molecules than there are cells.
  • Cells in an isotonic solution retain their shape.

• Concept of Osmolality and Milliequivalent

  • The unit for measuring solutes is the mole.
  • One mole is defined as the molecular weight of the solute in grams.
  • A solution's molarity is the number of moles of solute per liter of solution.
  • On the other hand, a solution's molality is the number of moles of solute per kilogram of solvent.
  • Concentration of solutions; part 2; moles, millimoles & milliequivalents by Professor Fink

• Osmosis

  • Osmosis is the movement of water across a membrane from an area of low solute concentration to an area of high solute concentration.
  • The semipermeable membrane limits the diffusion of solutes in the water.
  • If the volume of the solution on both sides of the membrane is the same but the concentrations of solute are different, then there are different amounts of water, the solvent, on either side of the membrane.
  • If there is more solute in one area, then there is less water; if there is less solute in one area, then there must be more water.
  • In this example, the solute cannot diffuse through the membrane, but the water can.

• Water and Solute Potential

  • The water potential in plant solutions is influenced by solute concentration, pressure, gravity, and factors called matrix effects.
  • Solute potential (Ψs), also called osmotic potential, is negative in a plant cell and zero in distilled water.
  • Solute molecules can dissolve in water because water molecules can bind to them via hydrogen bonds; a hydrophobic molecule like oil, which cannot bind to water, cannot go into solution.
  • Thus, Ψs decreases with increasing solute concentration.
  • This is why solute potential is sometimes called osmotic potential.

• Transport of Electrolytes across Cell Membranes

  • Osmotic pressure is influenced by the concentration of solutes in a solution.
  • It is directly proportional to the number of solute atoms or molecules and not dependent on the size of the solute molecules.
  • Because electrolytes dissociate into ions, adding relatively more solute molecules to a solution, they exert a greater osmotic pressure per unit mass than non-electrolytes such as glucose.
  • Facilitated diffusion of solutes occurs through protein-based channels.

• Introduction to Osmoregulation

  • The solutes in body fluids are mainly mineral salts and sugars.
  • An electrolyte is a solute that dissociates into ions when dissolved in water.
  • Solutions on two sides of a semi-permeable membrane tend to equalize in solute concentration by movement of solutes and/or water across the membrane.
  • In contrast, a cell shrivels when placed in a solution of high salt concentration.
  • Response of red blood cells in hypertonic, hypotonic, and isotonic solutions

• Kidney Function and Physiology

  • Almost all solutes, except for proteins, are filtered out into the glomerulus by a process called glomerular filtration.
  • Most of the solutes are reabsorbed in the PCT by a process called tubular reabsorption.
  • The "leaky" connections between the endothelial cells of the glomerular capillary network allow solutes to pass through easily.
  • Every solute, however, has a transport maximum; the excess solute is not reabsorbed.
  • The descending limb is permeable to water, not solutes; the opposite is true for the ascending limb.

• The Plasma Membrane and the Cytoplasm

  • It occurs when there is an imbalance of solutes outside of a cell versus inside the cell.
  • The solution that has the higher concentration of solutes is said to be hypertonic and the solution that has the lower concentration of solutes is said to be hypotonic.
  • Water molecules will diffuse out of the hypotonic solution and into the hypertonic solution (unless acted upon by hydrostatic forces).
  • If a membrane is permeable to water, though not to a solute, water will equalize its own concentration by diffusing to the side of lower water concentration (and thus the side of higher solute concentration).
  • In the beaker on the left, the solution on the right side of the membrane is hypertonic.

• pH, Buffers, Acids, and Bases

  • The pH of a solution indicates its acidity or basicity (alkalinity).
  • An acid is a substance that increases the concentration of hydrogen ions (H+) in a solution, usually by dissociating one of its hydrogen atoms.
  • An example of a weak basic solution is seawater, which has a pH near 8.0, close enough to neutral that well-adapted marine organisms thrive in this alkaline environment.
  • The pH scale measures the concentration of hydrogen ions (H+) in a solution.
  • Explain the composition of buffer solutions and how they maintain a steady pH

• Osmoregulation

  • Tonicity is the ability of a solution to exert an osmotic pressure upon a membrane.
  • In a hypertonic solution, water leaves a cell and the cell shrinks.
  • In an isotonic condition, the relative concentrations of solute and solvent are equal on both sides of the membrane.
  • Osmoreceptors are specialized cells in the brain that monitor the concentration of solutes in the blood.
  • The turgor pressure within a plant cell depends on the tonicity of the solution in which it is bathed.