Cellular Respiration…I think I’ve got it!

2 Nov

At my previous workplace, we typically devoted about 2 days to cellular respiration and photosynthesis in our freshman biology classes.

Yes, biologists, you read that correctly.  Two days.

Clearly, these topics are much more complex than 2 days worth of material.  Are they enough for 3 weeks, though, in a high school biology 1 class? 

This is what I’ve been struggling with over the past week and a half.  Since I’ve never taught this material in more detail than two days worth, it’s been challenging to recall some of the information I haven’t had to think about since I was in college.  Even the textbook we use (Biology: Exploring Life), which I really like, seems  a little too detailed over this particular unit.

I think I’ve managed, though, to get it narrowed down to where I want it.  Here’s what we covered for cellular respiration (we haven’t finished photosynthesis yet, so more on that later):

  • The overall equation for cellular respiration (and recognizing that the reactants in cellular respiration are the products in photosynthesis, and vice versa)
  • Glycolysis summary
  • Krebs Cycle summary
  • Electron Transport Chain and ATP Synthase summary

Here’s how we summarized each stage:

Glycolysis–

  • takes place in cytoplasm
  • splits glucose in half, forming 2 pyruvic acid molecules—-these go into the Krebs Cycle
  • also forms 2 NADH (we had to discuss what an electron carrier was, of course)—-these go to the ETC
  • net gain of 2 ATP

Krebs Cycle–

  • takes place in matrix of mitochondria
  • “strips off” carbons from the pyruvic acids, which become part of CO2 molecules
  • forms many more electron carriers (NADH and FADH2)—-go to the ETC
  • gain 2 more ATP

ETC and ATP Synthase–

  • found on the inner membrane of the mitochondria
  • electron carriers (NADH and FADH2) give up their electrons to the ETC, creating a H+ gradient
  • gradient powers the enzyme ATP Synthase, making 34 ATP
  • oxygen accepts the electrons and hydrogen from the electron carriers, forming H2O

    Mitochondrion

    Mitochondrion

We didn’t name all of the other enzymes involved, and we didn’t really mention acetyl coA (even though it was in the textbook).  It’s not perfect, but I think it makes a decent mix between only 2 days of coverage versus college-level detail.  We also discussed fermentation (what happens when there is little/no oxygen present), and I stressed the fact that plants, too, do cellular respiration (some students get confused and think that autotrophs do photosynthesis, making glucose, and therefore they don’t need to do respiration–they fail to see that the glucose still needs to be broken down to make ATP).

We also did a little dance with hand motions.  I’ll need to get the exact words later. 

What do you do to cover this particular topic?

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One Response to “Cellular Respiration…I think I’ve got it!”

  1. anatomypro November 2, 2010 at 4:43 PM #

    OMG! 2 days?!
    As an instructor in college, I do get to take a bit more time that than to MAKE SURE they’ve gotten it right! God bless you for hanging in there. Your crash course is phenomenal, so they are at least getting the basics.
    As for me, I go through EVERY step. I don’t leave one electron unaccounted. I still feel the issue is that the chemistry and physics behind the whole subject is lacking, so I make sure to start with that…”gentlemen, THIS is an electron…”

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