Cell Water Relations Flashcards
What are the 5 functions of water in plants?
- Water provides structural support
- Drives growth of cells and tissues
- Helps transport nutrients in xylem and sugars in phloem
- Is an electron donor during photosynthesis
- Lubricates the functions of plant cells - DNA, membranes, and enzymes lose their function without water
What are the properties of water?
- Water is a good solvent for polar compounds due to cohesion of its hydrogen bond’s
- Molecules on the surface have fewer hydrogen bonds, minimizing its surface area
- Often at a metastable state
Cohesion vs adhesion
Cohesion: attraction between the same substances
Ex: Hydrogen bonds of a water molecule
Adhesion: attraction between different substances
Ex: water molecule attaching to a hydrophilic surface
Why is ice less dense than water?
Compared to water ice has a greater amount and more stable hydrogen bonds, but the crystalline structure contains more gaps where molecules are able to push farther apart.
Properties: define metastable
Occurs when water is not in a state of equilibrium. Water transitions back to an equilibrium state only after a trigger
Ex: water in the xylem of plants - is a liquid rather than vapor due to cavitation
Metastable: name 3 examples
- Supercooled water: it can remain liquid below 0C
- Stretched water: liquid under tension (water in xylem)
- Glassy water: during below freezing temps, molecular structure are different than ice
Name 3 types of water movement
- Diffusion: movement of molecules under a concentration gradient over short distances
- Osmosis: movement of molecules through a semipermeable membrane
- Bulk flow: movement of masses of liquid and nutrients due to pressure difference
Define turgor pressure
Pressure exerted by a fluid in a cell that forces the membrane against the cell wall
Ex: watering a plant
Define aquaporins
Channel proteins that facilitate the transport of water across membranes, resulting in rapid plant movements
