Transcript Document
1 PROBLEM – What about physical pressure? physical pressure. It is easy to say that water will move from high concentration to low concentration…but look at the cell to the right…can the water keep going in? NO, as water enters and the cytoplasm begins to put pressure on the cell wall, the cell wall will begin push back (3rd law of motion) – physical pressure. The combined effects of __________________and __________________are given in a single measurement called the ___________________(Ψ; psi) for a given solution (EACH SOLUTION IS ASSIGNED A WATER POTENTIAL). WATER POTENTIAL How is water potential calculated? Ψ = water potential of the given solution 1. 2. 3. 4. physical pressure. WATER POTENTIAL physical pressure. How is water potential calculated? Ψ = Ψs + Ψp Ψ = water potential of the given solution Ψs = solute potential (osmotic potential) 1. 2. 3. WATER POTENTIAL physical pressure. How is water potential calculated? Ψ = Ψs + Ψp Ψ = water potential of the given solution Ψs = solute potential (osmotic potential) Ψp = [physical] pressure potential 1. 2. Quantitative analysis of WATER POTENTIAL Look at the four conditions on the right and explain what you are observing in terms of water potential. Water is moving from ____________________to ____________________________whose values are dependent on solute potential and pressure potential. More solute, more ______________Ψs More pressure _______________ Ψp Less pressure _______________ Ψp Quantitative analysis of WATER POTENTIAL Look at the four conditions on the right and explain what you are observing in terms of water potential. Quantitative analysis of WATER POTENTIAL 1. A solution in a beaker has sucrose dissolved in water with a solute potential of -0.5MPa. A flaccid cell is placed in the above beaker with a solute potential of -0.9MPa. a) What is the pressure potential of the flaccid cell before it was placed in the beaker? b) What is the water potential of the cell before it was placed in the beaker? c) What is the water potential in the beaker containing the sucrose? d) How will the water move? e) What is the pressure potential of the plant cell when it is in equilibrium with the sucrose solution outside? Also, what is its final water potential when it is in equilibrium? f) Is the cell now turgid/flaccid/plasmolysed? g) Is the cell hypotonic or hypertonic with respect to the outside? Quantitative analysis of WATER POTENTIAL 2. A solution in a beaker has sucrose dissolved in water with a solute potential of -0.7MPa. A flaccid cell is placed in the above beaker with a solute potential of -0.3MPa. a) What is the pressure potential of the flaccid cell before it was placed in the beaker? b) What is the water potential of the cell before it was placed in the beaker? c) What is the water potential in the beaker containing the sucrose? d) How will the water move? e) What is the pressure potential of the plant cell when it is in equilibrium with the sucrose solution outside? Think carefully – does the plant cell wall change shape? f) Also, what is the cell’s final water potential when it is in equilibrium? g) Is the cell now turgid/flaccid/plasmolysed? h) What is the cell’s solute potential when it is in equilibrium? I) Is the cell hypotonic or hypertonic with respect to the outside? J) If it is hypo/hyper (choose one) tonic – this means that its water potential is higher/lower (choose one) than the outside. Review Questions: Review Questions: