Biol. 3151: Week 3 Lab -­‐ FORUM DISCUSSION & ASSIGNMENT Winter 2015 DATA ANALYSIS, INTERPRETATION, & COMMUNICATION: Water and Solute Movement through RBC Membranes LEARNING OBJECTIVES • To understand the physiological bases for the RBC osmosis experiments and to interpret your data on these bases. • To understand and apply the norms/traditions of scientific presentation of research. • To apply the most effective ways of summarizing, analyzing, and presenting (thus communicating) your results. PREPARING FOR LAB You will need access to: (1) The document, “Introduction to Statistical Analyses & Graphing” (2) The Excel workbook, “RBC Osmosis 2015 Class Data” (3) A laptop, Excel, and Word (4) This document, “RBC Osmosis Lab Forum & Assignment Instructions” (5) The document, “RBC Osmosis Assignment Worksheet” (6) The lab instructions from last week, “RBC Osmosis Lab 2015” Review the following questions and be prepared to discuss the answers this week in lab. You are encouraged to review last week’s lab description and chapter 3 in your textbook (pp. 77-­‐80). (1) Why is molarity the most accurate measurement of a solution’s concentration? How are molarity and osmolarity related? (2) When we compare the relative osmolarities of two solutions (such as between the ICF and ECF), we use the terms hyperosmotic, isosmotic, and hyposmotic. What do these terms mean? How does the relative osmolarity between the ICF and ECF determine a red blood cell’s “response” (hypertonic, isotonic, or hypotonic) when placed in extracellular fluids that are hyper-­‐, iso-­‐, or hyposmotic to the internal fluids of the cell? How does solute permeability influence whether cells respond hypertonically, isotonically, or hypotonically when placed in extracellular fluids of varying concentrations? (3) Do the class results for the NaCl and urea experiments agree with what you expected based on your understanding of solute permeability and osmosis? Why or why not? Keep in mind that sheep RBCs are capable of swelling quite a bit before they hemolyze, and hemolysis is irreversible. (4) What are the fundamental questions/hypotheses for each of the three experiments? 1 (5) Focusing on Experiment III, do the class data agree with what you expected based on your understanding of solute permeability, osmosis, and the effect of temperature on membrane fluidity? (6) What do you think are the critical concepts that should be conveyed in your Results? (7) Which data need to be presented, and what do you think are the most effective ways of presenting your data (e.g. in a figure or table) that would best illustrate the critical concepts you’re trying to convey? (8) What makes a figure accurate and effective? (9) Which statistical tests do you think are appropriate for these data? (10) What is the full common name and full scientific name of the animal model used for these experiments? TASKS TO ACCOMPLISH BY THE END OF LAB (1) Complete the RBC Osmosis Assignment Worksheet (2) Create the three required figures THE RBC OSMOSIS GROUP ASSIGNMENT DUE DATES: Paper (hard) copy to instructor at the beginning of lecture on Monday, 2/2/15. Electronic copy uploaded to Assignment link on Blackboard by Monday night, 11:55 PM on 2/2/15. •
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COMPONENTS 1. For each experiment, provide a verbal description of results with appropriate statistics and the figure that supports this statement referenced. For example, “we found a significant negative linear relationship between extracellular NaCl concentration and mean cell response, as measured as % transmittance (p < 0.05, R2 = 0.87, y = -­‐1.2x + 20; Fig. 1).” 2. Provide three figures, one for each experiment. Provide adequately descriptive figure titles (placed BELOW each figure) and make sure the axes are clearly labeled with appropriate units identified (in parentheses). Only plot the SD error bars in the positive (+) direction. Sample Figure: (next page) 2 Mean arterial blood pressure
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Figure 1. The effects of two concentrations of epinephrine on mean arterial blood pressure (torr) over time (min) following epinephrine injection in the Rhesus monkey (Mucaca mulatta). Circles and solid lines indicate values for high concentrations of epinephrine (1:10,000), and squares and dashed lines indicate low concentrations (1:100,000). Error bars represent + 1 SD. (Note that you will only plot + 1 SD). 3. Provide a final draft of your conclusions and physiological explanations of the results from each experiment, and discussion of how the experimental evidence supports your conclusions. 4. Attach a copy of your group’s RBC Osmosis Assignment Worksheet. 5. DO NOT include data sheets (printouts of Excel spreadsheets) or statistical output summaries. Points will be deducted!!! FORMAT • Typed, 12-­‐point font. • Please run a spelling check and grammar check on your paper, making sure to correct any spelling or grammar mistakes (including figure titles). Also, proofread your paper for understandability and accuracy. • Indicate all team members’ names, lab section (1A or 1B) and date. 3