Natural Science - Year II
Unit 59: Krebs and Cellular Respiration
Science Weblecture for Unit 59
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Science Lecture for Unit 59: Cell Respiration
For Class
- Topic area: Biology: Cell Metabolism, Photosynthesis, Cell Respiration
- Terms and concepts to know: mitochondria, glycolysis, Krebs cycle, electron transport chain, fermentation
- See historical period(s): 20th Century Biology, Institutional Science
Lecture:
Cellular respiration is the process by which the mitochondria releases of stored energy so that the cell can do work—form other molecules, build proteins, move chemicals through its membrane. The cellular respiration reaction is also made of many steps, which are often broken down into two phases: the breakdown of glucose to pyruvic acid, followed by the Krebs cycle. The overall cellular respiration reaction is:
Notice that this is just the photosynthetic reaction in reverse! As with the photosynthesis reaction, each step has its own enzyme.
For a number of years, we used the animations at John Kyrk's website to show how glycolysis and the Krebs cycle worked. These Flash animations could be manipulated by students. When Flash support was discontinued in December 2020, the animations became unavailable.
However, by special permission from John Kyrk, we were allowed to create movie screen captures of the original animations last fall. While these are far more limited than the original animations, you can at least view the process and stop the video to study individual steps, labels and explanations.
Review the video on Glycolysis at the Scholars Online YouTube channel.
Review the video on the Krebs Cycle at the Scholars Online YouTube channel.
- Find at least one step in glycolysis and one in the Krebs cycle where the only thing happening is rearrangement of the molecule.
- Find at least one step in each process where the molecules gain atoms or atomic groups.
- Find at least one step in each process where the molecules lose atoms or atomic groups.
Study/Discussion Questions:
- How are cell respiration and photosynthesis similar? How do they differ?
- What do we mean by a "cycle" in the sense of the Krebs or Calvin cycles?
- Why are membranes important in both processes?
- In what part of the cell does each phase of the reaction take place?
Further Study On your Own (Optional)
- Check out Mitochondrial Mysteries Demystified, the website of the Biology Department at Taylor University.
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