When you first start an experiment, yeast cells have access to oxygen. However,
ID: 11771 • Letter: W
Question
When you first start an experiment, yeast cells have access to oxygen. However, after a while, yeast are in an anaerobic environment. If the yeast cells have the same energy requirement over the entire course of the experiment, when are yeast breaking down sugars at the fastest rate?A. when oxygen is present
B. when oxygen is absent
Packages of dry yeast contain materials other than yeast. There are binders and other compounds. Which of the tubes from last week’s experiment indicate that yeast cannot use these binders and other compounds as a food source?
A. tube 1 (containing water and glucose only)
B. tube 2 (containing water and yeast only)
C. tube 3 (containing yeast and glucose only)
D. tube 4 (containing boiled yeast and glucose only)
E. all
F. none
G. tubes 1 and 2
Why is it important to use replicates when you do your experiment this week?
A. to be sure that the result can be repeated in more than one replicate
B. because one tube may have been made up incorrectly or have some other type of problem
C. so you have more confidence in your results
D. all of these
E. none of these
In your proposal for the experiment you will conduct this week, you were required to write a step by step account of how you are going to conduct the experiment. All scientific journals require authors to provide a materials and methods section in which a detailed step by step account of how the experiment was conducted is provided. Why is it so important to give a step by step account of how the experiment was conducted?
A. so that others could repeat the experiment if they wish to do so
B. so that others know exactly what you did to come up with your results
C. so that others can evaluate if the author’s experimental design was correct
D. all of these
E. none of these
Sucrose consists of fructose and glucose joined together. To break apart sucrose, yeast cells need:
A. to add a very large amount of heat
B. an enzyme that lowers the amount of energy required to break apart sucrose
C. an enzyme that adds the energy required to break apart sucrose
D. nothing special, chemical bonds don’t contain energy so they come apart easily
NOTE: It would be even more spectacular if you could provide a quick explanation as I seem to have one of these wrong because I submitted it and it gave me a 4/5. I only have one more attempt. (MY ANSWERS were: A,B,D,D,B) Thanks!
Explanation / Answer
1. B. When oxygen is ABSENT. The anaerobic environment converts sugars quickly without the presence of oxygen. 2. B. Tube 2 because there is no usable energy in the test tube/ bag (whichever you used). There has to be a glucose present for the yeast to use it as energy and since water does not naturally contain glucose, then there is no energy breakdown occurring. 3. D. All of these because all of the choices have to do with proper science experiments. 4. D. All of these. Again these are all requirements of proper science experiments 5. B because enzymes lower the activation energy. *The only question you got wrong was the first. It is in the absence of oxygen.*
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