Pre-Lab Quiz 1) The three ways to measure cellular respiration include: consumption of O2, production of CO2 or the release of energy during the process. Which way will we use in this lab? 2) Write the equation for the ideal gas law and for cellular respiration. 3) How many respirometers will we make and use in this lab? 4) Name three items that will be placed inside these respirometers. 5) How often will we be taking a reading on the pipettes? How long will you do this for
Materials for each Buddy Pair • Graduated Cylinder (100ml) • 3 vials • 3 rubber stoppers • 3 washers • 3 glass pipettes (1 ml) • 1 Thermometer • 1 bulb pipette Shared items: • Cotton • Rayon • Blue Beads • Sharpie • Pea Seeds (Germinated & Dormant)
Overview • Determine the temperature of the water baths • Establishing the common volume of 10 seeds • Assembling the respirometers • Equilibrating the respirometers • Gather Data-Allow respiration to occur (30 min) • Breakdown-get ready for he next period
Determining Volume of 10 Germinating Seeds • Each pair will work with three vials. • Mark the vials “1, 2, 3” = Room temp bath • Mark the vials “4, 5, 6” = Water bath ↓ 10° C • Each Pair of people will work with a set of 3. • Starting with vials #1 and #4: -Add 50 ml water into the grad. cylinder -Add 10 germinating seeds -Record the ending volume in guide sheet -Take out seeds and place them on a paper towel labeled with the vial they will go into.
Determining Volume of 10 Germinating Seeds (cont’d) • Vials #2 and #5 : Non-germinating seeds & Beads -Add 50 ml of water to grad cylinder -Add 10 non-germinating seeds (dried up) -Add enough beads to reach the same volume of the germinating seeds -Take out seeds & beads place on a labeled paper towel • Vials #3 and #6 : Beads only -Add 50 ml of water and enough beads to reach the same original volume of the 10 germinating seeds. -Take out and place the beads on a labeled paper towel.
Assembling of the Respirometers • Place the following in all six vials: • 1 cotton ball (push to bottom of vial w/pencil) • Add 1 ml of KOH on the cotton using bulb pipette (**Keep of the sides of the vial and be careful !) • Add Rayon: pull off enough to be about the same size as the cotton ball • Place the corresponding peas and beads written on the towels into the correct vial. • Insert the non-tapered end of glass pipettes into the wide end of the black stoppers • Firmly insert stoppers w/pipettes into the vials. • Have it extend just beyond the bottom of the stopper
Assembling of the Respirometers(Cont’d) • Place a washer over each pipette tip and rest it on the top of the black stopper.** ***The Respirometers are now ready to go*** • Place a strip of Masking tape across each water bath tray. • Place Respirometers #1-3 In room temp bath • Place Respirometers #4-6 In the 10°C bath **Keep the tip of the pipettes out of the water** Allow the chambers to equilibrate for 7 minutes
During the Equilibrating Time Period • Place one drop of food coloring on the tip of each pipette • Read step 9 in your Guide • After 7 min. immerse all six respirometers in the water baths ****Do not let water to continue through the pipette and into the vial. If water continues all the way through remove it immediately. This means you have a leak and need to seal it.
Recording the Data • Allow the respirometers to equilibrate for 2 min. • After 2 min. take an initial reading for time “0” from your pipette and write in the table (0.01ml) • Take a temperature reading °C (0.1) • Watch the time and take a reading every 5 minutes for 30 minutes **Record all measurements in your data table
Clean up for Next Period • Be sure to clean and dry all equipment • Organize the items • Throw seeds away • Clean and dry each vial before you leave • Leave the water in the trays (add ice to one of them)
Filling Data in your Table • Notice a “Corrected Difference” Column for the germinated seeds & Dry peas w/beads • There is no “Corrected Difference” for the beads only column. • To determine the differences for each reading: (Initial reading @ time 0) – reading @ time X) • To determine your corrected differences: (initial reading @ time 0) – (reading @ time X) – (the difference of the beads alone for that time)
Generating a Graph • Independent Variable (x) = time (min) • Dependent Variable (y) = oxygen consumed (ml) • Be sure to graph a line for: • Germinating seeds @ room temp. • Germinating seeds below 10 C • Dry seeds @ room temp. • Dry seeds below 10 C
Analysis Questions – Guide sheets • Answer Questions #1-14 • Be sure to draw the graphs w/titles & labels • Be sure to show your work when determining the rate of respiration (#5) • Read each questions carefully, don’t forget to explain when it asks for it and to answer all the “why?” questions. Due Tomorrow.
Report: Summary of Your Results - Due: Monday Nov. 7 • Title • Purpose/importance/significance of the lab • Hypotheses (2): Write two predictions • ID Variables • Data table (written neatly & organized) • Graph of your data (IB hand drawn) • Analysis: Determine respiration rates for the germinating and non germinating seeds (ml/min) **Compare your data with the sample data and explain why your data might be different. • Conclusion and Evaluation: refer back to your hypotheses & assess your performance in the lab activity and all sources of error that might have occurred • Offer Suggestions on how to improve the lab