D2.3 Water potential

D2.3 Water potential

Solvation with water as the solvent

• Solute particles can dissolve in water to make a solution

• Water is polar with oxygen bing slightly negative and hydrogen slightly positive

• Watter molecules can form hydrogen bonds with neighbouring water molecules

  • Can also interact with solutes which are polar and ions

• In ionic compounds, the positive and negative ions are surrounded by water molecules and they cannot recombine

• When there are polar solute molecules, like sugar, hydrogen bonds are formed and the solute is pulled apart and dissolved

Hypotonic environment

• The solution has a lower concentration of solute (and a higher concentration of water) than the cell. 

• Water will move into the cell and burst cells (lysis)

• Contractile vacuole will pump out the excess water to stop the organism swelling and bursting

  • Vacoule expands -> pushing the cytoplasm against the cell wall

    • The pressure exterderd by the cell contents against the cell wall is called turgor pressure

      • Provides structural support to the cell and helps maintain its shape

Isotonic environment

• The solution has the same concentration of solute as the cell

• No net movement of water

• Water moves in and out of the cell -> cells don’t swell or shrink

• Organs being moved or stored for organ transplant -> medical application

Hypertonic environment

• The solution has a higher concentration of solute (& a lower concentration of water) than the cell

• Water will move out of the cell and cause shrinkage and crenation

  • Shrinkage away from the cell wall is known as plasmolysis

    • Leads to the loss of turgor pressure -> can result in wilting or collapse of the cell

    • In extreme cases, caan cause irreversible damage to the cell and disrupt its normal functioning