D2.3 Water Potential Flashcards
Explain why water molecules are polar.
Unequal sharing of electrons in the covalent bonds between oxygen and hydrogen (H₂O). Oxygen is more electronegative than hydrogen, meaning it can attract electrons toward itself - causing partial negatives, which results in a dipole moment, making the water molecule polar.
Explain why water is a medium for metabolic processes of cells.
- An excellent solvent, can dissolve polar and ionic compounds.
- Many biological reactions occur in aqueous environments.
- Solvent for reactants and products.
- Polar nature - separates charged molecules.
- Maintains optimal conditions for enzymatic activity through high specific heat capacity.
How is water able to regulate temperature?
High specific heat capacity - can absorb large amounts of heat energy without undergoing temp changes.
How is water’s temperature control important for the environment?
Allows the maintenance of plants and animals without major fluctuations in temperature.
Describe the impact of high heat vaporization.
When water evaporates, it absorbs a considerable amount of heat (energy), cooling the organism or its surroundings. E.g. sweating in mammals to regulate body temp.
How does water move from the roots to the leaves of trees?
- Evaporation of water from the leaves creates a negative pressure (tension) in the xylem vessels.
- The cohesive and adhesive properties of water molecules contribute to the capillary action that allows water to move upward against gravity.
- These properties enable water to form a continuous column in the plant’s xylem vessels, allowing it to be pulled upward from the roots to the leaves.
What is transpiration?
Water’s movement up a tree from its roots to its leaves.
What is a solute?
The “solute” is the substance that is dissolved in the solution; typically present in a smaller amount compared to the solvent. Can be liquid, gas, or solid.
What is a solvent?
The solvent is the substance in which the solute dissolves to form a solution - usually the component present in larger quantities. Solid, liquid, or gas.
What does hypertonic mean?
A solution with a higher concentration of solutes (such as salts or other molecules) compared to another solution.
What does hypotonic mean?
A solution with a lower concentration of solutes compared to another solution
What does isotonic mean?
A solution with the same concentration of solutes as another solution.
What happens to a cell when placed in hypertonic, hypotonic, and isotonic solutions?
Hypertonic: water tends to move out of the cell, leading to cell shrinkage or crenation.
Hypotonic: water tends to move into the cell, causing the cell to swell or potentially burst (lyse).
Isotonic: there is no net movement of water, and the cell maintains its shape and size.
Explain the role of electrolytes in maintaining proper cell function.
Influences osmotic balance and tonicity. (Imbalances can lead to hypertonic or hypotonic conditions affecting cell integrity).
What effect would a hypotonic medium have on a cell with no cell wall?
They will take in excess water, leading to swelling and potential bursting (lysis). E.g. a red blood cell in pure water.
What effect would a hypertonic medium have on a cell with no cell wall?
They will lose water, causing shrinkage and crenation.
How do contractile vacuoles function?
They maintain osmotic balance.
Why is it essential for freshwater unicellular organisms to have mechanisms, such as contractile vacuoles, for removing excess water?
Freshwater unicellular organisms face hypotonic environments, and contractile vacuoles actively pump out excess water to prevent cell swelling and bursting.
Why is it important for an IV solution to have salts in it?
Electrolytes maintain balance of ions. E.g. sodium, potassium, chloride, and others, play crucial roles in nerve function, muscle contraction, and maintaining proper fluid balance.
What would happen if you were given pure water in an IV?
If pure water were given in an IV without salts, it would create a hypotonic environment in the bloodstream - could lead to the influx of water into red blood cells, causing them to swell and potentially burst (hemolysis).
Formula for water potential:
Ψ=Ψsolute+Ψpressure
How is solute potential determined?
Determined by the concentration of solutes in the water. The more solutes present, the lower the water potential.
How is pressure potential determined?
Determined by physical pressure on the water. Positive when pressure is applied to the system and negative when pressure is exerted by the system.
What direction does water move regarding water potential?
Moves from regions of higher water potential to lower water potential. Follows the gradient established by the combined effects of solute potential and pressure potential.
What is the relationship between temperature and water potential?
As temperature increases, water molecules gain kinetic energy, and the water potential typically decreases.
What is the relationship between concentration and water potential?
An increase in solute concentration leads to a decrease in solute potential (Ψsolute), resulting in a lower overall water potential (Ψ). The more concentrated a solution, the lower its water potential.
What is the formula for the solute potential of a sucrose solution?
s = -iCRT
