Transport of Materials Worksheet (General Botany Lab) PDF

**NO PART OF THIS MATERIAL MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS \-\-- ELECTRONICALLY OR MECHANICALLY** **LBYBOTA (General Botany Laboratory)** **EXERCISE 4: TRANSPORT OF MATERIALS ACROSS THE CELL MEMBRANE AND CELL WALL (DIFFUSION, OSMOSIS, IMBIBITION)** **I. Introduction**...

**NO PART OF THIS MATERIAL MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS \-\-- ELECTRONICALLY OR MECHANICALLY** **LBYBOTA (General Botany Laboratory)** **EXERCISE 4: TRANSPORT OF MATERIALS ACROSS THE CELL MEMBRANE AND CELL WALL (DIFFUSION, OSMOSIS, IMBIBITION)** **I. Introduction** One of the most important functions of cell membranes is the maintenance of a steady living state or equilibrium in the midst of an ever-changing environment. This equilibrium is maintained by the regulation of the transport of substances into and out of the cell. Cellular activities such as growth, absorption, and respiration all involve the transport of dissolved substances through the cytoplasmic membranes. Transport across a membrane can either be passive or active, depending on the energy requirements of the process. **Simple diffusion** is a kind of passive transport. It is the tendency for dissolved molecules to move from a region of higher concentration to that of lower concentration. This process is possible only for solutes that are readily permeable such as nonpolar and small polar molecules. Water influences many activities of the cell, including cell growth, structural rigidity, and photosynthesis. It moves across cell membranes by simple diffusion. Because of its role in so many processes, the diffusion of water through a selectively permeable membrane has a special name: **osmosis**. Like solutes, water also has potential energy to flow to where it is less concentrated. Water flows passively from one place to another because of differences in potential energy. The tendency for water to move into and out of the cell is determined by the difference between cell contents and the external medium. The potential energy of water has a special name: **water potential or psi (Ψ~w~).** It represents the suction force of the cell or the difference between the activity of pure water and water in any other system. By general agreement, the water potential of pure water is zero. This means that the water potential of a solution has a negative value because the water is less concentrated than pure water. Also, water potential is expressed in units of pressure like megaspascals (Mpa) or bars. The relationship between water potential and its components may be expressed mathematically as: Ψ~w~ = Ψ~s~ + Ψ~p~ Where: If a cell is placed in a solution more concentrated than that in the vacuole, water is drawn out of the cell. As a result, the volume of the vacuole is reduced and the elastic cell wall is less distended, exerting less pressure on the protoplast. That point when the protoplast begins to pull away from the cell wall is called incipient plasmolysis. The continued loss of turgor causes the cytoplasm to shrink away from the cell wall. Osmotically-induced shrinkage of the cytoplasm is called **plasmolysis**. To demonstrate this, link to: Diffusion and Active Transport [[https://www.youtube.com/watch?v=eDeCgTRFCbA]](https://www.youtube.com/watch?v=eDeCgTRFCbA) Tonicity [[https://www.youtube.com/watch?v=FU9xE8rxnOo]](https://www.youtube.com/watch?v=FU9xE8rxnOo) [[https://www.youtube.com/watch?v=IMCj1Fm2RQ8]](https://www.youtube.com/watch?v=IMCj1Fm2RQ8) Water potential [[https://www.youtube.com/watch?v=jTDATlaBV-o]](https://www.youtube.com/watch?v=jTDATlaBV-o) **II. Objectives** At the end of this exercise, the student will be able to: 1. determine some factors that affect the diffusion process or the permeability of cell membranes; 2. differentiate between diffusion and imbibition; 3. determine how solute concentration in the external environment of a cell controls its turgor; 4. estimate the solute concentration of the cells in an epidermal tissue; and 5. estimate water potential of the storage tissue. **III. Methods** **Section A. Osmosis: Cell Changes in Plasmolysis\ ** Observe the experiment in this link: [[https://www.youtube.com/watch?v=OtPaPbVBMbM&feature=youtu.be]](https://www.youtube.com/watch?v=OtPaPbVBMbM&feature=youtu.be) Explain results of this experiment as shown in these images: **2.1. Temperature effect** **2.2. Organic solvent effect** Observe the following experiment in this link: [[https://www.youtube.com/watch?v=GklEQvy52L0]](https://www.youtube.com/watch?v=GklEQvy52L0) If you were to do the following experiment with red beets, what will be the expected result? Explain extensively your results. 1\. In 3 test tubes, put 5 pcs of 3cm cylinders of red beets**.** 2\. Add 10 ml of distilled water to test tube D, 10ml of 50% chloroform to tube E, and 10ml of 50% acetone to tube F 2\. Seal the tubes with corks to avoid escaping fumes. 3\. After 30 min, remove the beet sections and compare the red color intensity in each tube by +, ++, and +++. Record your observation in Table 2. **Section C. Imbibition** The uptake of liquid by hydrophilic surfaces accompanied by swelling is known as imbibition. Observe the following experiment in this link: [[https://www.youtube.com/watch?v=T5FhDDZzRMs]](https://www.youtube.com/watch?v=T5FhDDZzRMs) If you were to do the following experiment, what will be the expected result? Explain extensively your results. 1. Get wood, rubber and corn seeds weighed to approx. 20g each. Immerse these materials in beakers with water, and another set in kerosene. 2. Allow to stand for 90 minutes. After 90 minutes, get a large piece of blotting paper. Using a spatula, take out the wood, rubber and seeds immersed in water and gently blot dry. 3. Weigh the wood, rubber, and seeds. 4. Indicate if there is a gain or loss of weight as results in Table 3. **Section D. Determination of the Solute Concentration of Cells (Osmotic or Solute Potential Ψs) by the Plasmolytic Method** Observe the following experiment in this link: [[https://www.youtube.com/watch?v=kjKGIYybRq0]](https://www.youtube.com/watch?v=kjKGIYybRq0) This experiment is repeated as follows:   0.4M 0.5M  0.6M 0.7M 0.8M +-----------+-----------+-----------+-----------+-----------+-----------+ | Sucrose | Osmotic | Plasmolyz | Unplasmol | Total \# | \% | | | Potential | ed | yzed | of Cells | Plasmolyz | | Concentra | (bars) | | | Counted | ed | | tion | | Cells | Cells | | | | | | (\#) | (\#) | | | | (M) | | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.0 | -2.6 | | | | 0% | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.2 | -5.4 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.3 | -8.2 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.4 | -11.3 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.5 | -14.5 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.6 | -18.0 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.7 | -21.8 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0.8 | -25.8 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 1.0 | -30.2 | | | | 100% | +-----------+-----------+-----------+-----------+-----------+-----------+ *Allium cepa*   Table 5. +-----------+-----------+-----------+-----------+-----------+-----------+ | Salt | Osmotic | Plasmolyz | Unplasmol | Total \# | \% | | | Potential | ed | yzed | of Cells | Plasmolyz | | Concentra | (bars) | | | Counted | ed | | tion | | Cells | Cells | | | | | | (\#) | (\#) | | | | (M) | | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 0% | -2.6 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 1% | -5.4 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 2% | -8.2 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 3% | -11.3 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 4% | -14.5 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ | 5% | -18.0 | | | | | +-----------+-----------+-----------+-----------+-----------+-----------+ Note: a. convert the % concentration of NaCl to M, the molecular weight of NaCl is 58.44mole/L) b. Molarity = (g of solute/MW of solute) x 1 L **Percent to Molarity** **Example:** 3% = 3 g / 100 mL 3 g/ 100 mL = Xg / 1000 mL (3g) (1000 mL) = (Xg) (100 mL) (3g) (1000 mL)/ 100 mL = (Xg) (100 mL)/ 100 mL X = 30 g / L Molarity = (g of solute/MW of solute) x 1 L = (30 g /58.44 g/mol ) x 1 L **= 0.51 M** What is the **osmotic or solute potential** (Ψs) of the *Rhoeo discolor/Tradescantia* and *Allium cepa*? Show your computation. **Section E. Estimation of the Water Potential (Ψw) of Storage Tissue by Volume Change Method** Observe these experiments in these links: [[https://www.youtube.com/watch?v=jTDATlaBV-o]](https://www.youtube.com/watch?v=jTDATlaBV-o) [[https://www.youtube.com/watch?v=k1O9jBHgsxs]](https://www.youtube.com/watch?v=k1O9jBHgsxs) Estimates of water potential of various tissues have been obtained after equilibrating the tissues in solutions of different osmotic potentials. The principle depends upon finding the concentration of sucrose that would cause no change in weight of the tissue before and after an incubation period in the solution. This concentration may be assumed to have a water potential equal to that of the tissue. A similar experiment is as follows: Sucrose Concentration (Molarity) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Initial Weight (g) 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.0 Final Weight (g) 3.61 3.38 3.10 3.02 2.93 2.70 2.50 1.90 1.80 1.63 1.38 Δ Weight (g) % Weight Change Sucrose Concentration (Molarity) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Initial Weight (g) 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.0 Final Weight (g) 6.41 6.38 5.80 5.05 4.50 4.00 3.50 2.90 2.20 1.75 1.38 Δ Weight (g) % Weight Change What is the sucrose concentration at which zero percent change in weight is observed? What is the water potential Ψw of *Tradescantia* or *Allium cepa* cells? What is the water potential Ψw of the *Solanum tuberosum* potato cells? Note: The output of this activity is a SCIENTIFIC PAPER **Formative Learning (Labster Simulation)** Visit the Virtual Laboratory Works in your Canvas: 1. Cell Membrane and Transport: Learn how transporters keep cells healthy 2. Cell Membrane and Transport: Modifying the cell membrane (NEW) 3. Cell Membrane and Transport: Types of transporter proteins (NEW) **Submission Note:** 1. Save the document in x.pdf format with the file name: Section\_Group\#\_ Activity\# (ex. N03\_Group5\_Activity05) 2. Upload the file to the corresponding module under the submission page in the CANVAS. **Table of Contributions:** Indicate the work contribution of the group members below. Member with no participation will be graded zero (0). ---------- ------------------ ------------- **Name** **Contribution** **Remarks** **1.** **2.** **3.** **4.** **5.** ---------- ------------------ ------------- COPYRIGHT OF THIS MATERIAL (except video links) BELONGS TO: Biology Department De La Salle University **References** 1\. Barbour, M.G., B.A Bonner and G.J. Breckon. 1975. Botany. A Laboratory Manual. 5^th^ edition. John Wiley and Sons, Inc., New York. 2\. Balbach, M. and L.c. Bliss. 1991. A Laboratory Manual for Botany. 7^th^ edition. Saunders College Publishing, Orlando, Florida. 3\. Kaufman, P.B., A. Labavitch, J. Anderson-Prouty and N. Ghosheh. 1975. Laboratory Experiments in Plant Physiology. MacMillan Publishing Co., Inc. New York. 4\. Moore, R., W.D. Clark., K.R. Stern, and D. Vodopich. 1995. Botany. Wm. C. Brown Publishers. Dubuque, Indiana. 5\. Reiss, C. 1994. Experiments in Plant Physiology. Prentice-Hall, Inc., New Jersey. 6\. Vodopich, D.S. and R. Moore. 1989. Demonstrating the effects of stress on cellular membranes. The American Biology Teacher 51(1) : 40-42. COPYRIGHT OF THIS MATERIAL (except video links and photos) BELONGS TO: Biology Department De La Salle University