NAME _______________________________________________________ PER_____ LAB A: CELL ENERGY (25 PTS) : CELLULAR RESPIRATION (INTERACTIVE DEMONSTRATION) - PART I BACKGROUND:
All living cells, including the cells in your body and the cells in yeast, need energy for cellular processes such as pumping molecules into or out of the cell or synthesizing needed molecules. ATP is a special molecule which provides energy in a form that cells can use for cellular processes. Yeast are tiny eukaryotic cells that produce CO2 or Carbon Dioxide as they convert glucose and oxygen to carbon dioxide and water during cellular respiration. Yeast produces gas by feeding on the sugars in flour, and expelling carbon dioxide in the process and that makes bread rise. Yeast is tiny: Just one gram holds about 25 billion cells. That amount of fungi can produce a significant amount of carbon dioxide, provided it has the simple sugars it uses as food. The three sugars that will be tested are glucose (blood sugar), sucrose (table sugar), fructose (fruit sugar).
When the yeast respire aerobically ,oxygen gas is consumed at the same rate that CO2 is produced—so there would be no change in the gas pressure in the flask, and the balloon would not inflate . However, when yeast ferments the sugars anaerobically, CO2 production will cause a change in the pressure of a closed flask, since no oxygen is being consumed, and the balloon will inflate.
In this lab, you will also use Bromothymol blue as an indicator to show the whether CO2 is produced by the yeast cells as well as measure the amount of CO2 gas produced using latex balloons to trap the CO2.
1. PURPOSE: __________________________________________________________________________________
MATERIALS:
Baker’s yeast (4 g) Sugar Water Fruit Juice Sugar Substitute
1 cup warm water (105° F) 3 large balloons Bromothymol Blue Solution Transfer pipettes (3)
Label Tape Paper towels Flasks (3)
PROCEDURES:
1. Stretch out the balloon by blowing it up repeatedly, and then lay it aside. 2. Add yeast, *sugar and warm water into the flask and stir. 3. You’ll notice the water bubbling as the yeast produces carbon dioxide. 4. Attach the balloon to the mouth of the flask, and set both aside. 5. Take your initial circumference measurement 6. Do not move the flask 7. Repeat this process for each type of sugar 8. After a few minutes, you’ll notice the balloon standing upright. If you don’t see anything happen, keep
waiting. Eventually, the balloon will inflate. 9. Use string to record the circumference of your balloon in 5 minute interval for 40 minutes
Once you have completed the steps 1-8, 10. Remove the balloon from the flask (carefully, as liquid may be inside) 11. Use a transfer pipette to transfer 6mL of yeast solution into a test tube 12. Add 1mL of BTB (Bromothymol Blue indicator) to the tube 13. Observe noting color change 14. Continue to observe the color changes for up to 5 minutes 15. Smell the flask, note the smell.
Bromothymol Blue Indicator Colors When the Bromothymol Indicator is BLUE it means… When the Bromothymol Indicator is YELLOW it means… When the Bromothymol Indicator is GREEN it means…
DATA Data Table 1: Growth of Balloon
Time (min) Circumference (cm) Time (min) Circumference (cm) Glucose Fructose Splenda Glucose Fructose Splenda
0 25 5 30 10 35 15 40 20
Graph: construct a graph showing the change in circumference over time. ***remember your TAILS!!!***
1. EQUATION: Write out the equation for cellular respiration _________________________________________________________________________________________
2. What is the independent variable? _________________________________________________________________________________________
3. What is the dependent variable? _________________________________________________________________________________________
4. What is the purpose of the indicator Bromothymol blue? _________________________________________________________________________________________
5. List at least 3 things you know about yeast from previous labs? __________________________________________________________________________________________________________________________________________________________________________________
6. What does the color change of the tube containing yeast represent? _________________________________________________________________________________________
7. How do you know if the yeast produced CO2 and not some other gas that blew up the balloon? __________________________________________________________________________________________________________________________________________________________________________________
8. What test did you do to verify it was CO2? ________________________________________________________________________________________
9. What are the two types of Cellular Respiration ________________________________________________________________________________________
10. Which type of cellular respiration one took place in this lab? ________________________________________________________________________________________
11. How do you know? ________________________________________________________________________________________
12. Describe the relationship between CO2 levels and pH levels __________________________________________________________________________________________________________________________________________________________________________________
13. Do ALL CELLS GO through cellular respiration? _______________ Explain your answer! ________________________________________________________________________________________________________________________________________________________________________________________
Name __________________________________________________ Date ___________________ Class ____________ Photosynthesis Virtual Labs Tutorial: http://www.harcourtschool.com/activity/science_up_close/512/deploy/interface.html Watch and listen to the tutorial found in the link above. Fill in the following answers as you watch. Stop and replay anything you don’t understand – this is a complicated topic!
1. Plants use photosynthesis to make __________________ for the plant.
2. What do plants need in order to perform photosynthesis?
3. How is the plant able to obtain each “ingredient?”
4. Identify the plant cell organelle in which photosynthesis takes place. ________________________
5. Summarize the process of photosynthesis. Water and carbon enter the chloroplast….. ___________________________________________________________________________________________
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6. What happens to the oxygen that is produced as a result of photosynthesis?
7. Name at least 2 reasons why is photosynthesis also important for people and animals? ___________________________________________________________________________________________
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Virtual Lab #1 ‐ http://www.reading.ac.uk/virtualexperiments/ves/preloader‐photosynthesis‐full.html Bubbles are given off by the plant through photosynthesis. By measuring the rate at which the bubbles are produced
it is possible to tell how fast the plant is photosynthesizing. Read and follow the directions on how to use this lab
simulator. Press start and record the bubbles per minute for each of the following light distances. Graph your data
and don’t forget your TAILS!
Light Distance (cm)
Bubbles per
minute 100
120
150
180
200
8. Based on your data, draw a conclusion regarding how light intensity affects the rate of photosynthesis.
Virtual Lab #2 ‐ http://www.kscience.co.uk/animations/photolab.swf In this lab, you will be experimenting with how different variables affect the rate of photosynthesis.
9. Set the thermometer to 25°C (Room Temperature) and the light intensity to 20. a. What were the bubbles per minute at this setting? ______ bpm b. Now increase the CO2 available to the elodea. What were your bubbles per minute? ______ bpm c. Based on your data, how does the amount of available CO2 affect the rate of photosynthesis?
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10. Keep your settings from 9c (25°C, light intensity of 20, increased CO2).
a. What were the bubbles per minute at this setting? ______ bpm
b. Now increase the temperature to 40°C. What were your bubbles per minute? ______ bpm
c. Based on your data, how does an increase in temperature affect the rate of photosynthesis?
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11. Return to your settings from 9c (25°C, light intensity of 20, increased CO2). a. What were the bubbles per minute at this setting? ______ bpm b. Now decrease the temperature to 10°C. What were your bubbles per minute? ______ bpm c. Based on your data, how does a decrease in temperature affect the rate of photosynthesis?
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12. Alter the variables in order to determine which combination leads to the highest rate of photosynthesis. Which combination of settings produced the highest number of bubbles per minute?
a. Temperature: ________
b. Light: ________
c. CO2: ________
Photosynthesis Tutorial: http://www.phschool.com/science/biology_place/biocoach/photosynth/overview.html Use this site to answer questions about photosynthesis.
13. Write the chemical equation for photosynthesis.
14. Photosynthesis converts _________________ energy into the ____________________ energy of sugars and
other organic compounds. 15. In the blank portion of this paper, draw the picture which shows the overall process of photosynthesis
