LABORATORY PRACTICE BIOLOGY – 8TH GRADE CELLULAR RESPIRATION AND METABOLISM MATERIALS – Per Group (6 students) Lab Coat 1 Chronometer 1 Roll Paper Towel 1 Roll Masking Tape 1 Black or Blue Permanent Marker Latex Gloves (3 pairs per student) 1 Dozen Plastic transparent cups (no white cups) 1 Dozen Plastic Straws 1 Kilogram Baker’s Yeast (powder) 1 Kilogram Sugar 1 Dozen Plastic Teaspoons
INSTRUCTIONS DO NOT proceed with any action unless indicated by your teacher. When indicated, proceed cautiously and safely for yourself and your other classmates. Observe all the materials, reactions and processes involved in the experiment. Record information in the tables provided, you are allowed to use cameras to record the activity, only to document the activity for your lab report.
PROCEDURE 1. Put on lab coat, safety goggles, and gloves. 2. Fill a clean, transparent plastic cup, halfway with room temperature water. 3. Add several (5 to 10) drops of bromothymol blue to the water. Swirl to mix the solution. Bromothymol blue is a skin and eye irritant. 4. Insert a clean straw into the solution. Gently blow a steady stream of air through the straw. Note any changes in the solution’s appearance. Be careful not to accidentally drink the solution while blowing into the straw. 5. Label 3 plastic cups as: “A”, “B” and “C”, and your group number. 6. Fill cup A with ice water, fill cup B with room temperature water, and fill cup C with warm water. 7. Add several (5 to 10) drops of bromothymol blue to each cup to ensure a uniform appearance. 8. Add ¼ teaspoon of baker’s yeast to each cup. Swirl the cups, and observe the appearance of the solutions every 30 s. 9. After 5 min, examine the surface of each solution with a hand lens. 10. Clean up your lab materials according to your teacher’s instructions. 11. Wash your hands before leaving the lab. 12. Add ¼ teaspoon of sugar to each tube, observe and record your information.
Cup
A B C
Time 1 (30 seg)
Time 2 (60 seg)
Time 3 (90 seg)
Time 4 (5 min)
Time 5 (10 min)
Time 6 (15 min)
QUESTIONNAIRE 1. (3 p) Did the yeast produce a similar color change? Explain your answer. 2. (4 p) Did temperature affect the yeast’s production of carbon dioxide? Explain your answer. 3. (4 p) What did you observe on the surface of the solutions? 4. (4 p) Did adding sugar to the yeast solution affect the respiration rate? 5. OPTIONAL 1: (2.5 p) Design a method for inquiry that would test the effects of various sugar concentrations on yeast metabolism. 6. OPTIONAL 2: (2.5 p) Make a graph showing the changes in the cups over time.