Water potential and osmosis

• What is solvation?


  Solvation is the combination of a solvent with the molecules or ions of a solvent. Due to attractions, water molecules form a shell around the ions and charged particles, preventing them from clumping together. This is important because the cytoplasm is solute, and allows metabolism to occur.
• What is the definition for osmosis?

  Osmosis may be defined as a net movement of water from a hypotonic to a hypertonic solution due to the attraction between solute and water. Solutes are osmotically active is intermolecular attractions form between them and water.
• Why does osmosis occur?

  Intermolecular attractions between solutes and water are even stronger than the hydrogen bonds holding water together, which is why solutions are more viscous than water- the attractions restrict the movement of the individual water molecules. This is why in osmosis, there is a net movement of water from a less concentrated solution, hypotonic, to a more concentrated solution, hypertonic. There is no net movement between two isotonic solutions because there is no difference between the concentrations of osmotically active solutes, known as dynamic equilibrium.
• What is standard deviation?

  Standard deviation is a measure of the range of variation from the mean. To calculate standard deviation, first calculate the mean. Then calculate how far each value is from the mean square them, and find the average of those values. Then square root.
• What is standard error?

  Standard error is the measure of how reliably the mean of a sample estimates the mean of a whole population, found by dividing the the sample standard deviation by the square root of the sample size
• What is normal saline?

  Isotonic solutions are used during medical procedures- usually what is known as 'normal saline', containing sodium chloride. Normal saline may be safely introduced to a blood system via an IV, used to rinse skin abrasions, used to keep areas of damaged skin moistened, used in eye drops, and frozen to a slush to keep donor organs cool.
• What is osmolarity?


  Osmolarity is defined as the measure of the concentration of solute particles in a solution- and this is done through the number of osmole of solute per litre of solution.
• What is an osmole?

  An osmole is the number of particles in a solute that will split into ions when in solution.
• What are aquaporins?

  Although the phospholipid bilayer of the plasma membrane is hydrophobic, water molecules are small enough to pass through it. Some cells (such as root hair or kidney cells) have water channels known as aquaporins, increasing membrane permeability to water. Aquaporins are specialized membrane proteins that form channels in the cell membrane specifically for water molecules to pass through. The outside of the protein is hydrophobic allowing it to be embedded within the hydrophobic core of the membrane, but the channel is hydrophilic, allowing a faster rate of water movement across the membrane.
• What happens to an animal cell in a hypotonic solution?

  In an animal cell is placed in a hypotonic solution, it will gain water via osmosis and swell. Because it does not have the support of a cell wall, it will burst.
• What happens to an animal cell in a hypertonic solution?

  If an animal cell is placed in a hypertonic solution, it will lose water via osmosis, so the cytoplasm will shrink, but the area of plasma membrane will not change, so the cell will develop indentations known as crenations.
• What happens to a plant cell in a hypotonic solution?

  A plant cell placed in a hypotonic solution will gain water via osmosis and swell, but not burst- it is turgid. Turgid plant tissue provides support due to its strength under compression (in stems and leaves).
• What happens to a plant cell in a hypertonic solution?

  If a plant cell is placed in a hypertonic solution, it will loose water via osmosis. The pressure of the cytoplasm will decrease, and it will no longer push against the cell wall- the cell will be flaccid. This is seen as wilting, observed in plants that have lost too much water. The process of the plasma membrane pulling away from the cell wall may be known as plasmolysis and is damaging, usually causing cell death.