Krebs Cycle Calculator

The Krebs Cycle Calculator tracks the energy-carrying molecules produced during the citric acid cycle — the second stage of cellular respiration where cells extract energy from nutrients. Enter the number of Acetyl-CoA molecules and complete cycles, then select your calculation type (per cycle, total, or per glucose molecule) to see your Total ATP Equivalent, plus a breakdown of NADH, FADH2, GTP, and CO₂ produced. Toggle Include Pyruvate Oxidation to factor in NADH generated during the conversion of pyruvate to Acetyl-CoA.

molecules

Enter the number of acetyl-CoA molecules entering the cycle

cycles

Number of complete Krebs cycle turns

Include NADH produced during pyruvate to acetyl-CoA conversion

Results

Total ATP Equivalent

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NADH Produced

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FADH2 Produced

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GTP Produced

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CO₂ Produced

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Results Table

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Frequently Asked Questions

How many ATP molecules are produced per Krebs cycle?

One complete Krebs cycle produces 1 GTP (equivalent to 1 ATP), 3 NADH (equivalent to 7.5 ATP through electron transport), and 1 FADH2 (equivalent to 1.5 ATP), totaling 10 ATP equivalents per cycle.

What is the difference between NADH and FADH2 in ATP production?

NADH produces approximately 2.5 ATP molecules through the electron transport chain, while FADH2 produces about 1.5 ATP molecules. This difference is due to FADH2 entering the electron transport chain at a later point.

Why does one glucose molecule result in two Krebs cycles?

Glucose is broken down into two pyruvate molecules during glycolysis. Each pyruvate is converted to one acetyl-CoA, which then enters the Krebs cycle. Therefore, one glucose molecule results in two complete Krebs cycles.

What happens to the CO₂ produced in the Krebs cycle?

The CO₂ produced during the Krebs cycle is a waste product that is released from the cell. In multicellular organisms, CO₂ is transported to the lungs and exhaled as part of cellular respiration.

Is GTP the same as ATP in the Krebs cycle?

GTP (guanosine triphosphate) is functionally equivalent to ATP and can be readily converted to ATP. In the Krebs cycle, one GTP is produced per cycle, which is counted as one ATP equivalent in energy calculations.

What is pyruvate oxidation and why include it?

Pyruvate oxidation is the conversion of pyruvate to acetyl-CoA before entering the Krebs cycle. This step produces one NADH per pyruvate molecule and is often included in Krebs cycle calculations since it's directly linked to the cycle.

How does the electron transport chain relate to Krebs cycle products?

NADH and FADH2 produced in the Krebs cycle are electron carriers that donate electrons to the electron transport chain, where most ATP is actually produced through oxidative phosphorylation.