Cell Structure and Function Tonicity and pH

Question: #6467

Cell Structure and Function - Tonicity and pH complete solution correct answer key

Exercise 1: The Case of the Limp Vegetable

Results:

Table 1: Comparison of States of Tonicity

Conclusions:

A. How does each potato strip look? Which one is limp and which one is crisp?

B. How can the difference be explained?

C. What caused the change in appearance of each strip?

Discussion:

A. Did the experiment support or refute the initial hypothesis? Explain why.

B. Explain why vegetables stored in a refrigerator over time become limp.

C. In this exercise two of the three types of tonicity gradients were observed. Suggest an experiment to provide an example of the third type of tonicity gradient in action.

D. What kinds of cell environmental conditions might affect tonicity in cells?

Exercise 2: Turgor

Results:

Table 2: Comparison of Turgor Pressure States in Elodea Leaf Cells

Conclusion:

A. How can the differences in appearance of the cells in the two solutions be explained?

B. What caused the appearance of the cell to be altered by using 10% NaCl solution instead of water?

C. In what direction did the water move in the hypotonic solution? In the hypertonic solution?

D. Plasmolysis refers to the movement of water out of the cell, thus causing the central vacuole to become smaller. The volume of the entire cell is reduced and the plasma membrane may be visible, separated from the cell wall, because it pulls away from the cell wall with the reduction in volume. In which turgor state would this be most likely to occur?

Discussion:

A. Did this exercise support or refute the initial hypothesis? Explain.

B. Where might an example of this turgor pressure adjustment be observed happening in nature or around your home?

Exercise 3: Buffering Effect and pH

Results:

Table 3: Initial and Ending pH Comparison for Test Tube Solutions

Table 4: Results of Acid Addition to Buffered Solutions

Conclusions:

A. What was the initial pH of the water in test tube #1?

B. What was the pH of the water after the addition of acid?

C. What was the initial pH of test tube solutions #2 and #3?

D. What was the pH after adding 5 drops of acid in each of test tubes #2 and #3?

E. When did the pH appreciably change?

F. What caused this dramatic shift in pH?

Figure 1: Graph of pH Change in Response to Buffering

Discussion:

A. Did this experiment support or refute the initial hypothesis? Explain.

B. Why did this pattern occur?

C. What was the difference between solutions #2 and #3?

D. What difference was observed in the way the two solutions reacted to the addition of acid?

E. Why is the buffering capacity of organic substances so important to living organisms, including humans?

Laboratory Summary:

What did you learn from doing this laboratory?

References (must be in correct format for credit):

Solution: #6483

Cell Structure and Function - Tonicity and pH

COPY OR SAVE TO A WORD PROCESSING PROGRAM to fill out and hand in to your instructor Name:___________________________Date:________________________ Cell Structure and Function – Tonicity and pH Exercise 1: The Case of the Limp Vegetable Results: Table 1: Comparison of States of Tonicity Test Tube Solute/Solvent Appearance of Potato Strip Type of Tonicity Gradient: Is the potato strip in a Hypertonic, Hypotonic or Isotonic at the beginning of this exercise? 1 Sugar solution Crispy Hypotonic solution 2 Salt solution Limp Hyper tonic solution Conclusions: A. How does each potato strip look? Which one is limp and which one is crisp? Answer The potato strip in first test tube appears crispy, while in other appears limp. That is the potato strip present in sugar solution is crispy, while in salt solution is limp. B. How can the difference be explained? Answer The difference is due to concentration of solution, C. What caused the change in appearance of each strip? Answer If solution is less concentrated (sugar solution) than potato, its water enters in it and provides potato’s strip a crisp appearance, but if it is more concentrated than potato, then, water from potato comes outside and potato’s strip limps. Discussion: A. Did the experiment support or refute the initial hypothesis? Explain why. Answer Yes, as initially, our hypothesis was that, salt solution may provide limp appearance to potato, hence, it has been proven true, B. Explain why vegetables stored in a refrigerator over time become limp. Answer As, with the passage of time, dehydration occurs so, due to removal of water, they appear limp. C. In this exercise two of the three types of tonicity gradients were observed. Suggest an experiment to provide an example of the third type of tonicity gradient in action. Answer In third kind of experience, we may take a solution, that is isotonic with water and will not show any effect on its appearance as no, net movement of water will take place. D. What ki...