Biology

Lab 3- Cell Structure and Function

Your Name:

INSTRUCTIONS:

· On your own and without assistance, complete this Lab 3 Answer Sheet electronically and submit it via the Assignments Folder by the date listed in the Course Schedule (under Syllabus).

· To conduct your laboratory exercises, use the Laboratory Manual located under Course Content. Read the introduction and the directions for each exercise/experiment carefully before completing the exercises/experiments and answering the questions.

· Save your Lab 3 Answer Sheet in the following format: LastName_Lab3 (e.g., Smith_Lab3).

· You should submit your document as a Word (.doc or .docx) or Rich Text Format (.rtf) file for best compatibility.

Pre-Lab Questions

1. What is the water potential of an open beaker containing pure water?

1. Why don’t red blood cells swell or shrink in blood?

1. How do osmotic power plants work?

1. Research the structures that protect plant and animal cells from damage resulting from osmotic pressure. Write a few paragraphs explaining what they are, how they work, and where they are located.

Experiment 1: Osmosis Direction and Concentration Gradients

Data Tables

Table 5: Sucrose Concentration vs. Tubing Permeability

Band Color Sucrose % in Beaker Sucrose % in Bag Initial Volume (mL) Final Volume (mL) Net Displacement (mL)
Yellow
Red
Blue
Green

Post-Lab Questions

Hypotheses (write one hypothesis for each bag):

Yellow bag:

Red bag:

Blue bag:

Green bag:

1. Insert a picture of your results here:

2. Do your results support your hypotheses? Did the volume in each bag change as predicted based on the known tonicity of each bag? Explain.

3. If the results were unexpected, discuss the possible reason(s) your results deviated from your hypothesis.

4. Using the known sucrose concentrations inside each of the tubing pieces and their respective beakers, identify whether the solution inside the tube was hypotonic, hypertonic, or isotonic in comparison to the beaker solution it was placed in.

Yellow:

Red:

Blue:

Green:

5. Which tubing increased the most in volume? Why?

6. What would happen if the tubing with the yellow band was placed in a beaker of distilled water?

7. How are excess salts that accumulate in cells transferred to the blood stream so they can be removed from the body? Explain how this process works in terms of tonicity.

8. How is this experiment similar to the way a cell membrane works in the body? How is it different? Be specific with your response.

9. If you wanted water to flow out of a piece of dialysis tubing filled with a 50% sucrose solution, what would the minimum concentration of the beaker solution need to be? Explain your answer using scientific evidence.

Experiment 2: What Household Substances are Acidic or Basic?

Data Tables

Table 6: pH Values of Common Household Substances

Substances pH Prediction pH Test Strip Color
Acetic Acid (Vinegar)
Sodium Bicarbonate Solution (Baking Soda)

Post-Lab Questions

1. Insert a picture of your results here:

1. What is the purpose of determining the pH of the acetic acid and the sodium bicarbonate solution before testing the other household substances?

1. Compare and contrast acids and bases in terms of their H+ ion and OH- ion concentrations.

1. Name two acids and two bases you often use.

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