Tonicity of Solutions

Tonicity of Solutions

• Tonicity refers to the ability of a solution to affect cell shape by altering internal water volume through osmosis.

Hypertonic Solutions

• Definition: A hypertonic solution has a higher solute concentration compared to inside the cell.

• Prefix Meaning: "Hyper" means above or beyond.

• Example: Saltwater is a common hypertonic solution.

• Effect on Cells:

  • Water moves out of the cells, leading to cell shrinkage or "shriveling".

  • Example Scenario:

    • Salad Wilt: When salt in salad dressing is applied to lettuce, it draws water out of the cells through osmosis, causing them to wilt.

    • Slug Experiment: Pouring salt on a slug draws water out of its body, potentially leading to the slug's death.

• Illustration:

  • Cell: 98% water / 2% sodium chloride

  • Solution: 96% water / 4% sodium chloride

  • Conclusion: Outside has higher solute concentration, causing water to exit the cell.

  • Consequences: Using salt to water plants causes them to lose water and potentially die.

Hypotonic Solutions

• Definition: A hypotonic solution has a lower solute concentration compared to inside the cell.

• Prefix Meaning: "Hypo" means below or under.

• Effect on Cells:

  • Water moves into the cells, which can lead to swelling or bursting of animal cells (which lack a cell wall).

  • Beneficial for plant cells due to turgor pressure keeping them rigid and upright.

• Example Scenario:

  • Produce Section: Use of water misters in grocery stores keeps vegetables fresh by causing them to absorb water, leading to a crisp appearance.

  • Watering Plants: Applying fresh water allows plants to absorb water and maintain structural integrity.

Isotonic Solutions

• Definition: An isotonic solution has an equal concentration of solutes compared to the inside of the cell.

• Prefix Meaning: "Iso" means same.

• Effect on Cells:

  • No net water movement; thus, cells remain the same size as water moves equally in and out.

• Example Scenario:

  • Saline IV: Hospital saline solutions are isotonic to blood (approx. 0.9% salt) so they do not alter cell size and effectively rehydrate patients without causing harm.