d2.3 water potential Flashcards
(16 cards)
what is solvation?
solvation is the process by which solvent molecules surround and interact with solute molecules. a solute is any substance that is dissolved by a solvent molecule to form a solution. solutes that are able to be dissolved by a solvent are considered to be soluble.
why is water the universal solvent?
water is commonly referred to as the universal solvent due to its capacity to dissolve a large number of substances. water can dissolve any substance that contains charged particles or electronegative atoms. the polar regions of the water molecule associate with molecular surfaces that have an opposing charge, forming dispersive hydrogen shells.
how does osmosis move water molecules?
osmosis is a special form of simple diffusion that involves the movement of free water molecules. while water is a polar molecule, it is small enough to move between phospholipids in the bilayer. as a polar molecule, it is attracted to and will associate with other polar molecules or charged ions. water will therefore move towards the solution containing a higher concentration of ions or polar molecules.
water is a solvent capable of dissolving any polar or charged molecule (solute) to create a solution.
what are hypertonic solutions?
solutions with relatively higher solute concentrations are categorised as hypertonic (high solute → gains water)
what are hypotonic solutions?
solutions with relatively lower solute concentrations are categorised as hypotonic (low solute → loses water)
what are isotonic solutions?
solutions that have equivalent solute concentrations are categorised as isotonic (same solute → no net water flow)
how can you investigate the osmolarity of a tissue?
the osmolarity of a tissue may be interpolated by bathing the sample in solutions with established solute concentrations. the tissue will lose water when placed in hypertonic solutions and gain water when placed in hypotonic solutions. water loss or gain may be determined by weighing the sample before and after bathing in solution. tissue osmolarity may be inferred by identifying the concentration of solution at which there is no weight change.
what are the effects of osmosis on cells with a cell wall?
in plants and fungi, the effects of uncontrolled osmosis are moderated by the presence of an inflexible cell wall. in hypertonic solutions, the cytoplasm will shrink (plasmolysis) but the cell wall will maintain a structured shape. in hypotonic solutions, the cytoplasm will expand but be unable to rupture within the constrains of the cell wall (turgor). excess water may be stored in a large, central vacuole that has its own membrane.
what are the effects of osmosis on cells that lack a cell wall?
in cells that lack a cell wall, uncontrolled osmosis will have negative effects with regards to cell viability. in hypertonic solutions, water will leave the cell causing it to shrivel (crenation). in hypotonic solutions, water will enter the cell causing it to swell and potentially burst (lysis). in multicellular organisms, it is therefore important that tissue fluid remains isotonic to prevent harmful changes.
how do unicellular organisms regulate osmosis?
unicellular organisms (such as protists) may possess a contractile vacuole to regulate the osmotic conditions within the cell. excess water is absorbed into the contractile vacuole, causing it to swell. the vacuole then fuses to the plasma membrane and contracts, expelling the water. the amount of water expelled and the rate of contractions are determined by the extracellular conditions.
what are the medical applications of isotonic solutions?
tissues or organs to be used in medical procedures must be kept in solution to prevent cellular dessication (completely dried up). this solution must share the same osmolarity as the tissue/organ in order to prevent osmosis from occurring.
isotonic solutions can also be delivered intravenously to restore fluid levels to patients with hypovolemia (low blood plasma levels).
what is the definition of water potential?
water potential can be defined as ‘the potential energy of water, per until volume, relative to pure water’. as solutes are added to solution, the water potential decreases into negative values - solutions with a high solute concentration have a lower water potential.
in terms of potential energy, in what direction does water move?
water molecules move from an area of higher potential energy to an area of lower potential energy. water potential describes the tendency of water molecules to move from a dilute solution to a solution with a high solute concentration.
how does solute and pressure potential affect water potential?
the water potential of a solution is influenced by several factors, including solute potential and pressure potential. solute potential is the effect that solutes in a solution have on water potential. pressure potential is the hydrostatic pressure to which water is subjected. the total water potential for a solution is the sum of its solute potential and its pressure potential.
what are the effects of hypotonic solutions on plant tissue?
when plant tissue is placed in a hypotonic solution, water moves from the surrounding solution into the plant cell down its water potential gradient. the inward movement of water increasing pressure potential as the cytoplasm presses against the cell wall. plants in this state are turgid and will provide structural support to the plant.
what are the effects of hypertonic solutions on plant tissue?
when plant tissue is placed in a hypertonic solution, water moves out of the plant cell into the surrounding solution down its water potential gradient. the loss of water from the plant cell will result in a reduced volume of cytoplasm and a decreased pressure potential inside the cell. plant cells will lose turgor pressure and the plant will begin to wilt.
