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The Citric Acid Cycle is such a challenging thing to teach because there are so many details. Some teachers simply skip over the details and just give students the net reaction to recite and regurgitate. I have taught it many times and I think the details are what make respiration (and biology in general) beautiful to understand. There are a few key learning goals I have for my students when they study the Citric Acid Cycle:
1. This is an enzymatic process (the enzymes aren’t shown in my diagram to make sure things don’t look TOO complicated. In my glycolysis activity, I show the enzymes and when students do the citric acid cycle activity, I tell them that enzymes are also involved but we don’t need to see every single one.
2. The citric acid cycle starts off with oxaloacetate, add in 2 carbons (in acetyl-CoA), and along the way, you remove two CO2. You end up with oxaloacetate again at the end. So you go from 4 to 6 carbons in the cycle, and then back down to 4 to start the cycle over again.
3. The surprising thing to students is that the cell went through all this work and all it gets it 1 GTP (which converts to ATP) and 2 from glycolysis. “That’s it??!” Until they see oxidative phosphorylation, NADH and FADH2 energy carriers are meaningless to students. I tell my students that it seems like the cell did a ton of work for almost nothing, but WAIT UNTIL TOMORROW’s lesson!! It adds a little intrigue and interest to a chapter that seems a little dull and slow to a lot of students.
4. I also make sure to note the location of the citric acid cycle (inside the mitochondrial matrix) and the location of glycolysis (cytosol). This is important later because the NADH from glycolysis “uses” some of its energy to get to the oxidative phosphorylation process inside the mitochondria, yielding fewer ATP (about 2 ATP each) than would be expected from NADH already inside the mitochondria (3 ATP each).
With this activity, you can copy the cut-out sheets on colored paper if you would like, to make their charts colorful.
I have included two versions: 1 where oxygen atoms are shown and 1 where oxygen atoms are not. You can choose which one meets your class needs. The oxygen atoms help students to see where CO2 comes from, but they aren’t necessary to get the point across that the number of carbons goes from 4 to 6 back to 4 again.
Included in this activity are the following:
Three question and reading pages (and answer keys) – Page 1 has 2 versions, showing/not showing oxygen for pyruvate oxidation step
1 cut-out page with molecules with oxygen shown
1 cut-out page with molecules with no oxygen shown, just carbons
1 paste page
1 answer key with molecules of oxygen shown
1 answer key with molecules with no oxygen shown, just carbons
Check out my other Respiration and Photosynthesis Resources
Light Dependent Reactions Coloring Page, Reading, and Questions
Calvin Cycle Cut and Paste Activity
Glycolysis Cut-and-Paste Activity
If you have any questions, suggestions, or corrections, please leave a question on the question and answer section of my store and I will get back to you quickly!
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