Review of Glycolysis, Krebs Cycle and the Electron Transport Chain, the 3 metabolic pathways required to convert carbohydrates (glucose) to energy (ATP). PLUS, test your knowledge with our free printable diagrams designed for dietetic students to help prepare them for their next DPD course exam on these complex pathways.
How Does the Body Convert Carbohydrates into Energy?
The body uses a series of metabolic pathways to convert carbohydrates into energy. These metabolic pathways include Glycolysis, Krebs Cycle, and the Electron Transport Chain. The energy produced during these pathways helps keep us focused and active throughout the day. We can become tired, irritable, and find it hard to concentrate on the task at hand when we don’t eat enough carbohydrates, or don’t eat enough in general. So, if you haven’t done so already, go grab something to eat before you continue reading. You don’t want to study on an empty stomach. Your brain with thank you.
Now that you’ve grabbed a snack, let’s continue talking about food and how it converts to energy. Conversion of carbohydrates to energy begins with that first bite of pasta (or any carbohydrate of your choice). I’m going to use pasta as an example because it’s a great source of carbohydrates and it’s my favorite food group. Just kidding, pasta isn’t a food group, but it should be.
As you enjoy your plate of pasta, the pasta makes its way through the GI tract and is eventually absorbed as glucose. Glucose is taken up by the cells, and enters the cytosol. This is where the first metabolic pathway called Glycolysis begins. Glycolysis coverts glucose into pyruvate and produces a net total of 2 ATP. Pyruvate is then converted into acetyl-coA to be used in the next metabolic pathway, called the Krebs cycle. The Krebs cycle produces 3 NADH, 1 FADH2, and 2 ATP from 1 acetyl-coA. NADH and FADH2 from the Krebs cycle is then used in the third and final pathway, called the Electron Transport Chain. The electron transport chain produces about 32 ATP giving a grand total of 36 ATP produced from 1 glucose.
Breakdown of the 3 metabolic pathways:
- Occurs in the cytosol
- Converts 1 glucose into 2 pyruvate
- Produces net 2 ATP
aka TCA cycle, citric acid cycle
- Occurs in the mitochondria
- Pyruvate converts into acetyl-CoA before entering the Krebs cycle
- Coverts 1 acetyl-CoA into 3 NADH, 1 FADH2
- Produces net 2 ATP
Electron Transport Chain
aka respiratory chain
- Occurs in the mitochondria
- Converts NADH and FADH2 into 32 ATP
Reminder: Glycolysis, the Krebs cycle and the Electron Transport Chain are complex pathways involving multiple reactions. I intentionally left out a certain details of these metabolic pathways because I want to focus on the big picture of converting carbohydrates into energy. I recommend referring to your text book and credible resources to learn more about the step by step reactions in each of these processes. You may also refer to the text books listed in the References section below.
Why Should RDs2B Know These Metabolic Pathways?
Our bodies are amazingly complex, and as a nutrition student you are learning so much more about these complexities than you ever wanted to. While earning my dietetics degree, I was blown away at the amount of science-based nutrition topics I had to learn. I just wanted to talk to people about food, so why did I have to study the Krebs cycle?
Majority of Registered Dietitians don’t think twice about the Krebs cycle, unless they’re a college professor or work in research. It’s just one of those topics that all RDs2B must learn as a dietetic student, regardless if they plan on using it in their career. You could also say that learning Glycolysis, the Krebs cycle and the Electron Transport Chain is a rite of passage for dietitians.
However, you may be asked to share your professional opinion on CoQ10 and NADH supplementation someday. At which point, all those memories of studying the metabolic pathways may come flooding back and you’ll be reminded about how much you LOVED learning about Glycolysis, the Krebs cycle and Electron Transport Chain.
Sign-up to access our free printable diagrams for Glycolysis, Krebs Cycle and the Electron Transport Chain. These fillable diagrams are perfect to help test your knowledge and prepare you for their next DPD course exam on these metabolic pathways.
Click on the articles below to read about the current research and recommendations for Registered Dietitians on carbohydrates and how to address CoQ10 supplements within their scope of work, with additional information on NADH supplements.
A total of 36 ATP can be produced from 1 glucose. This energy conversation is possible through a series of 3 different metabolic pathways: Glycolysis, Krebs Cycle, and the Electron Transport Chain. Glycolysis coverts glucose into pyruvate and produces a net total of 2 ATP. Pyruvate is converted into acetyl-coA before entering the Krebs cycle. The Krebs cycle produces 2 ATP in addition to NADH and FADH2, which are used in the Electron Transport Chain to produces about 32 ATP.
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Test your knowledge with printable diagrams for Glycolysis, Krebs Cycle and the Electron Transport Chain.
Appling, D. R., Anthony-Cahill, S. J., Mathews, C. K. (2016). Biochemistry: Concepts and Connections. Pearson Education, Inc.
Gropper, S. S., Smith, J. L. (2013). Advanced Nutrition and Human Metabolism (6th ed.). Wadsworth Cengage Learning.
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