D.2.3 SL Flashcards
Explain water as a solvent.
Solvation is the interaction of the solvent with the dissolved solute. Polar molecules such as ions will dissolve in water since they are hydrophilic. Ions are atoms that have lost or gained electrons meaning they can either have a positive or negative charge. Nonpolar molecules are unable to dissolve since they are hydrophobic and they clump to each other when exposed to water (lipids). Covalent compounds (glucose and oxygen) can also dissolve in water because they form intermolecular interactions with the dipolar water molecules even though they may mot dissociate into ions.
What are the different levels of water concentration and what can they lead to?
Hypertonic solutions have a high concentration of solute and lower concentration of water outside the cell. This would lead to the cell shrinking as the water moves out of the cell causing plasmolysis. Hypotonic solutions have a low concentration of solute and higher concentration of water outside the cell. This would lead to the cell possibly bursting as the water moves into the cell causing cytolisis. Isotonic solutions have similar levels of concentration of solute and water which means they are typically at an optimal level.
Explain the movement of water by osmosis.
Osmosis is the net movement of water molecules from a region of high water concentration to a region of lower water concentration. It happens through a partially permeable membrane in areas like the kidney. In a hypotonic solution the water will move into the cell and in a hypertonic solution the water will move out. In an isotonic solution there is no movement of water.
State the effects of water movement on cells without cell wall.
Hypotonic solutions have a low concentration of solute and higher concentration of water outside the cell. This would lead to the cell possibly bursting as the water moves into the cell causing cytolisis. Unicellular cells have contractile vacuoles which actively expel water from the cell as an adaptation. Humans have a constant isotonic environment to prevent water gain or loss.
State the effects of water movement on cells with a cell wall.
Cells with a cell wall maintain structure better meaning they don’t burst but rather maintain their shape. Instead, there is an increase in internal pressure which is also known as turgor pressure. This pressure is exerted by the cytoplasm against the cell wall and causes a cell to be turgid. The water then leaves the cell through osmosis causing the plant to shrink and the plasma membrane to move away from the cell wall. This process is called plasmolysis and causes a loss of turgor pressure.
Explain the medical applications of isotonic solutions.
The solutions must have the same water concentration as the cytoplasm of the cells in the body to prevent excess water loss or gain. Fluids may be given intravenously in medical settings which allows rapid and direct absorption into the circulatory system or the replacement of lost fluids. Organs are stored in these solutions to replicate our interior environment and keep them alive
