Slide 1 / 36 Slide 2 / 36 New Jersey Center for Teaching and Learning AP BIOLOGY Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of Investigation #6 students and teachers. These materials may not be used for any commercial purpose without the written Cellular Respiration permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Summer 2014 www.njctl.org Click to go to website: www.njctl.org Slide 3 / 36 Slide 4 / 36 Pacing/Teacher's Notes Investigation #6: Cellular Respiration Click on the topic to go to that section · Pacing/Teacher's Notes · Pre-Lab · Guided Investigation - Microrespirometers · Independent Inquiry Return to Table of Contents Slide 5 / 36 Slide 6 / 36 Pacing Teacher's Notes General Reference Lab procedure adapted from College Board AP Biology Day (time) Activity to Unit Plan Notes Description Investigative Labs: An Inquiry Approach Teacher's Manual Pre-Lab Day 1 (HW) Pre-lab Day 16 HW questions Glue Prep Click here for CB Day 2 (10) Respirometer if Day 17 Respirometers needed AP Biology Teacher Manual Learn how to Guided use Day 3 (80) Day 18 Practice respirometers or sensors Test factor's Independent Day 4 (40) affect on Day 19 Invesigation respiration rate Independent Analysis and Day 5 (40) Day 20 Investigation sharing
Slide 7 / 36 Slide 8 / 36 Pre-Lab Question/Objectives What factors affect the rate of cellular respiration in multicellular organisms? In this lab we will: · Learn how a respirometer system can be used to measure respiration rates in plant seeds or small invertebrates, such as insects or earthworms. · Design and conduct an experiment to explore the effect of certain factors, including environmental variables, on the rate of cellular respiration. · Connect and apply concepts, including the relationship between cell structure and function (mitochondria); strategies for capture, store, and use of free energy; diffusion of gases across cell membranes; and the physical laws pertaining to the properties and behaviors of gases. Return to Table of Contents Slide 9 / 36 Slide 10 / 36 Pre-Lab Questions Pre-Lab Questions Read the background information and answer the following 3. Imagine that you are given 25 germinating pea seeds that questions in your lab notebook. (from pg. S73 of student lab have been placed in boiling water for five minutes. You place manual) these seeds in a respirometer and collect data. Predict the rate of oxygen consumption (i.e., cellular respiration) for these seeds and explain your reasons. 1. Why is it necessary to correct the reading of the respirometers containing seeds with the reading taken from respirometers containing only glass beads? Your answer should refer to the 4. Imagine that you are asked to measure the rate of respiration concepts derived from the general gas law: PV = nRT. for a 25 g reptile and a 25 g mammal at 10 o C. Predict how the results would compare, and justify your prediction. 2. What happens to the volume of the gas being measured when 5. Imagine that you are asked to repeat the reptile/mammal the temperature or pressure changes during the experiment? If comparison of oxygen consumption, but at a temperature of pressure and temperature remain constant, will the volume of 22 o C. Predict how these result would differ from the gas in the respirometers increase or decrease? Explain. measurements made at 10 o C, and explain your prediction in terms of the metabolism of the animals. 6. What difficulties would there be if you used a living green plant in this investigation instead of germinating seeds? Slide 11 / 36 Slide 12 / 36 Safety Guided Investigation - You must wear safety goggles or glasses, aprons, and Microrespirometers gloves during this investigation because KOH (or the alternative, NaOH) is caustic. Follow your teacher's instructions when using the hot glue gun to seal the microrespirometers. Do not work in the laboratory without your teacher's supervision. Return to Table of Contents
Slide 13 / 36 Slide 14 / 36 Materials Constructing Microrespirometers You need to assemble two microrespirometers, one for measuring the rate of respiration in germinating seeds and one · 1 mL plastic tuberculin syringes without needles · 40 microliter plastic capillary tubes or plastic microhematocrits for the control. · hot glue gun Step 1 Plug in hot glue gun and allow it to heat up. · manometer fluid (soapy water with red food coloring) · germinating/nongerminating Wisconsin Fast Plants seeds or seeds of several species of plants, including grasses Step 2 Take a tuberculin syringe (without a needle) and make · small animals, such as crickets or earthworms sure that its plunger is pushed all the way in. · small glass beads or dry baked seeds · absorbent cotton Step 3 Carefully insert a 40 microliter plastic capillary tube into · nonabsorbent cotton the syringe where the needle normally would be. Insert it as far · 15% solution of KOH or NaOH as the plunger tip but no farther. This will help prevent the · thin-stem plastic dropping pipettes capillary from becoming plugged with glue. · 3 or 4 flat metal washers · thermometer · centimeter ruler · glass-marking pens · constant-temperature water bath Slide 15 / 36 Slide 16 / 36 Constructing Microrespirometers Guided Investigation Step 4 While holding the capillary tube straight up, add a small Step 1 Draw a small quantity of manometer fluid (soapy water about of hot glue around its base (where it meets the syringe) to with red food coloring) into the full length of the seal the capillary to the syringe. Keep the capillary pointed microrespirometer's capillary tube. Then eject the fluid back out straight up until the glue cools - this should not take long. If of the capillary. This coats the inside of the tube with a thin needed, add a bit more glue to ensure an airtight seal between soapy film that helps prevent the manometer fluid from sticking. the capillary and syringe. Step 2 Carefully insert a small plug of absorbent cotton into the Step 5 After the glue has barrel of the microrespirometers, all the way to the 0 mL or cc cooled, pull back on the mark. You can pack this cotton to the end with the barrel of a plunger and make sure that clean thin-stem pipette. the glue has not plugged the capillary. If the capillary is plugged, carefully remove the Step 3 Add one small drop of 15% KOH (or NaOH) to the cotton glue and capillary and start in the microrespirometers. Do not add too much! over. Slide 17 / 36 Slide 18 / 36 Guided Investigation Guided Investigation Step 4 Add a small plug of nonabsorbent cotton on top of the Step 7 Add 0.5 mL of germinating seed to one of the absorbent cotton plug already inside the barrel of the microrespirometers. Push the plunger in to the 1.0 mL mark. microrespirometers. You can pack the cotton to the end with the This creates a sealed microrespirometer chamber with a 1.0 mL barrel of a clean thin-stem pipette. volume. Step 5 Slowly reinsert the syringe plunger. Be sure to point the Add 0.5 mL of beads or baked seeds to the second capillary tip into a sink or container. There may be excess KOH microrespirometer. Reinsert the syringe plunger and push it to in the syringe that might squirt from the end of the capillary. the 1.0 mL mark to create your control chamber. Push the plunger in until it reaches the cotton so that any excess KOH is removed. Step 8 Place three to four washers around the barrel of the microrespirometers. The washers provide weight so that the Step 6 Remove the plunger to add seeds/beads. microrespirometers will sink.
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