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ATP Yield Calculator

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About This MicroSim

This interactive visualization decomposes the ATP produced per glucose molecule across glycolysis, pyruvate oxidation, and the citric acid cycle. A dynamic table and proportional pie chart update instantly when students change the conversion factors for NADH and FADH₂, illustrating why modern biology textbooks report ~32 ATP whereas older references cited ~38.

Key Visual Elements

  • Stage Table: Shows substrate-level ATP, oxidative ATP from NADH, oxidative ATP from FADH₂, and the stage total.
  • Pie Chart: Animates the relative contribution each stage makes to the overall ATP budget.
  • Context Tips: Hovering any stage row reveals where the reactions take place and why they matter.

How to Use

  1. Start in the default Modern (~32 ATP) mode that uses 2.5 ATP/NADH and 1.5 ATP/FADH₂ conversion factors.
  2. Hover over each stage row to review the anatomical location (cytosol vs. mitochondrial matrix) and main products.
  3. Drag the NADH and FADH₂ sliders to explore how shuttle efficiencies or membrane leakiness alter the net ATP tally.
  4. Press the toggle button to jump to the Classic (~38 ATP) assumption and observe how the pie chart shifts when NADH and FADH₂ are given more generous yields.
  5. Have students explain why substrate-level ATP remains constant while oxidative phosphorylation changes with slider inputs.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

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<iframe src="https://dmccreary.github.io/biology/sims/atp-yield-calculator/main.html"
        height="610px"
        width="100%"
        scrolling="no"></iframe>

Learning Objectives

  • Calculate the total ATP produced per glucose at each stage of cellular respiration using adjustable NADH and FADH₂ conversion factors.
  • Compare modern (~32 ATP) and classic (~38 ATP) assumptions and justify why current estimates are lower.
  • Interpret visual data (table + pie chart) to explain why the citric acid cycle dominates ATP yield despite producing only two substrate-level ATP.

Controls

  • Mode Toggle: Switches between preset modern and classic conversion factors.
  • NADH Slider (1.5–3.0 ATP): Adjusts oxidative phosphorylation yield per NADH.
  • FADH₂ Slider (1.0–2.0 ATP): Adjusts oxidative phosphorylation yield per FADH₂.
  • Show Pie Labels: Optional checkbox to declutter the chart during discussion.

Data and Calculations

Stage Substrate ATP NADH Produced FADH₂ Produced Notes
Glycolysis 2 2 0 Occurs in the cytosol before pyruvate enters mitochondria.
Pyruvate Oxidation 0 2 0 Converts pyruvate to acetyl-CoA in the mitochondrial matrix.
Citric Acid Cycle 2 6 2 Completes oxidation of acetyl-CoA, producing most reduced coenzymes.

The simulation multiplies NADH and FADH₂ counts by the selected conversion factors, adds substrate-level ATP, and reports both a numeric and proportional breakdown.

Lesson Plan

Grade Level

9–12 (AP/IB Biology) and introductory undergraduate biology

Duration

15 minutes (including short discussion)

Prerequisites

  • Students can list the stages of cellular respiration in order.
  • Students know what NADH and FADH₂ are and that they donate electrons to the ETC.
  • Students understand substrate-level vs. oxidative phosphorylation.

Activities

  1. Predict & Observe (5 min): Ask students to estimate how much ATP each stage supplies before touching the sliders. Then reveal the default visualization.
  2. Parameter Sweep (5 min): In pairs, students drag the NADH slider from 1.5 to 3.0 and note how much the total ATP fluctuates. Repeat for FADH₂.
  3. Explain (5 min): Groups summarize why the modern estimate is lower (membrane leak, shuttle costs) and report which stage is most sensitive to slider changes.

Assessment

  • Quick exit ticket: “Which slider affects total ATP more and why?”
  • Ask students to describe how the citric acid cycle can remain the largest contributor even when slider values change.
  • Optional: Have students screenshot the table in classic mode and annotate the biochemical rationale.

References

  1. Freeman, S. Biological Science, 7e. Pearson, 2024 — Chapter on Cellular Respiration.
  2. Nelson, D. & Cox, M. Lehninger Principles of Biochemistry, 8e. W.H. Freeman, 2021.
  3. Alberts, B. Molecular Biology of the Cell, 7e. Garland Science, 2022.