Lewis/Life - Teaching Techniques

Chapter 7 - Teaching Techniques

A. General Tips
Much early research into carbohydrate metabolism centered on the work of Carl Neuberg, who identified acetaldehyde in 1911, and Otto Meyerhoff, who found that the coenzymes necessary for alcohol fermentation are also found in muscle cells. The pathway we now call glycolysis was for many years called the Embden-Meyerhoff pathway.
Hans Krebs figured out the essentials of the cycle named for him in 1940. Our understanding of that cycle has been modified only slightly in the last half century.
I urge you to stress to your students that the respiratory events discussed in this chapter are common throughout the living world. Plants "do" cellular respiration the same as animals. Students often think that respiration is limited to the animals.
Your two biggest concerns with this chapter will be first, your awareness of the needs of your class and second, your understanding of the charts and diagrams.
There is a tremendous amount of information in this chapter and it is presented in such a way that you can go into as much or as little depth as you see fit. I recommend you examine your course objectives and the direction your course is taking, along with the backgrounds of your students. Decide which points need to be stressed. If your class is a pre-requesite for pre-med majors, your emphasis may be far different than if your class is a general education class designed strictly for non-science majors. Obviously, the depth with which you teach the energy pathways will vary greatly -- as will the specific points of emphasis.
Your second concern will be the charts. Lewis has included some excellent charts, but not all students see charts the same way. I suggest you go over all the charts very carefully so that you are completely comfortable with the way Lewis has diagrammed the information. This may be the only source of information the students have outside of class time. Be sure you understand exactly how Lewis has set up the information so that you can help the students with any problems they may have. You may also wish to use one or more of the charts as focal points for your lectures.
This chapter lends itself very nicely to the practical application of the scientific method. Notice particularly Table 7.2 where Lewis has specifically outlined the scientific method in connection with chemiosmosis. You might also use Figure 7.13 and its accompanying legend to demonstrate the scientific method in action.
You might wish to copy and distribute to your students the Overview of Chapter Objectives flowchart found at the beginning of this Instructor's Manual Chapter.
B. Possible Approaches to the Chapter
For students who have never had this material before (and even for some who have!), the information in this chapter can be overwhelming. The use of clear reference charts can help you streamline the presentation of this material.
Look at Figure 7.5. This diagrammatic overview of cellular respiration is repeated with Figures 7.9, 7.10, 7.11, and 7.14 to explain each part of the respiratory pathway. I suggest using either this figure or a similar diagram to keep students on track. Notice how the rest of the above mentioned figures are expansions of a particular portion of the concept.
Figure 7.9 is better than comparable drawings found in most other texts because this figure uses simple diagrams to show phosphorylation and because it follows glucose to two molecules of pyruvic acid (instead of just one with a note that the process is doubled after the split).
Figure 7.11 is also better than many comparable drawings because it simplifies the formation of the nucleotide molecules.
If your students are having any particular difficulty with glycolysis or the Krebs cycle, I suggest you have them follow the respective diagram while you read either a prepared statement or the appropriate paragraphs in the text.
C. Hints Related to Specific Chapter Topics
- I. The problem is differentiating between "breathing" respiration and cellular respiration. Lewis does a good job of showing the student right from the start that these two respirations are different -- yet similar. Note particularly Figure 7.1 where Lewis specifically says the two respirations are linked. Many books don't say this and the students often don't quite see the connections.
- II. Glycolysis is the key pathway; it is also the focal point of this entire discussion.
  Note on page 127 -- both in the text and in Figure 7.3 -- that "fermentation pathways" is plural. So often students tend to think of fermentation being a singular concept.
- II.B. Two points that students might question come up in this section. Lewis calls cellular respiration quite efficient. Eight pages later the estimated yield of ATP is discussed. If any of your students are purist, simply remind them that theoretically cellular respiration is really much more than quite efficient.
  The theoretical yield is 36 ATP's for eukaryotes and 38 for prokaryotes. Some of your students may have learned that the number is 38 for all cells. This is a matter of semantics. Eukaryotes use two ATP's just to get the products into the mitochondria so that the cycle can continue. Some books simply discount this usage saying that a yield is a yield.
- IV.A. The enzyme that splits the fructose-1,6-biphosphate is aldolase.
- VI. Lewis correctly mentions that the Krebs Cycle is also called the citric acid cycle. Some of your students may have learned another alternate name, TCA (tri-carboxilic acid) cycle.
- VII.A. Some writers set up the respiratory chain to look like a series of gears. If your class is mechanically oriented, this may be a valuable analogy.
- VII.B. Keep in mind that chemiosmosis follows all the rules of "regular" osmosis.
- IX. Lewis points out that plants use lipids. This point should be stressed. Students so often do not understand that plants utilize the same nutrients as other organisms.