Cellular Respiration Diagram: Stages, Locations, and Energy Flow

One Glucose, Four Linked Stages

A cellular respiration diagram explains how cells transfer energy from glucose into ATP. In an aerobic eukaryotic model, the route links glycolysis, pyruvate oxidation, the Krebs cycle and oxidative phosphorylation. Keeping the compartments visible is as useful as memorizing the stage names.

The diagram below separates carbon flow from the transfer of reducing equivalents. All yields refer to one glucose, and ATP totals are approximate. Use the cellular respiration diagram generator when you need a teaching version with a different level of detail.

AcaDraw original teaching schematic, informed by OpenStax Biology 2e §§7.2–7.4. This is a compartment and process guide, not a drawing of mitochondrial anatomy or a measured metabolic-flux chart. Most transport steps and intermediates are omitted.

Stages, Sites, Inputs, Outputs and ATP Yield

Inputs are a teaching summary rather than fully balanced reaction equations. The Krebs cycle regenerates its carbon acceptor, oxaloacetate. Most cycle enzymes are in the matrix, but succinate dehydrogenase is embedded in the inner mitochondrial membrane.

Glycolysis: Start Outside the Mitochondrion

Glycolysis occurs in the cytosol. It splits a six-carbon glucose into two three-carbon pyruvate molecules. Two ATP are invested early, and four are produced later, giving a net gain of two ATP. Two NAD⁺ are also reduced to two NADH.

A cellular respiration diagram should make the difference between gross and net ATP explicit. Writing “4 ATP from glycolysis” without subtracting the investment overstates the net yield.

Glycolysis does not directly consume oxygen. It can continue without aerobic respiration when other pathways regenerate NAD⁺, as in fermentation. That does not mean the full aerobic pathway can keep running normally without oxygen.

The Link Reaction: Pyruvate Becomes Acetyl-CoA

Before entering the Krebs cycle, pyruvate-derived carbon enters the mitochondrial pathway. Pyruvate oxidation converts two pyruvate into two acetyl-CoA, releases two CO₂ and generates two NADH per glucose. No ATP is made directly at this stage.

Leaving out this link reaction can make a cellular respiration diagram appear to send pyruvate straight into the cycle. Keep the conversion visible even if your course groups it with the Krebs stage.

Carbon dioxide is released here and during the cycle. Glycolysis itself does not release CO₂ in this standard glucose pathway.

Krebs Cycle: Count Two Turns per Glucose

Each acetyl-CoA supplies a two-carbon group to the cycle. Because one glucose produces two acetyl-CoA, the cycle turns twice per glucose. Those two turns yield four CO₂, six NADH, two FADH₂ and two ATP equivalents, which may be formed as ATP or GTP depending on the enzyme context.

The cycle's main contribution to the final ATP tally is its production of reduced electron carriers. Most ATP is made downstream when their reducing equivalents feed oxidative phosphorylation.

Be careful with tables that quote “per turn.” One ATP equivalent, three NADH and one FADH₂ per turn become twice those amounts per glucose. Do not combine per-turn and per-glucose values in the same total.

Electron Transport and Chemiosmosis

At the inner mitochondrial membrane, the electron transport chain transfers electrons ultimately to oxygen. Coupled proton pumping moves H⁺ from the matrix into the intermembrane space, building an electrochemical gradient. Protons then return toward the matrix through ATP synthase, supporting ATP production.

Oxygen is the final electron acceptor and is reduced to water. It does not belong on an input arrow into glycolysis. A diagram showing ATP synthase should also distinguish its proton-return direction from the chain's proton-pumping direction.

NADH made in the cytosol does not simply cross the inner membrane. Shuttle systems transfer its reducing equivalents into the mitochondrial pathway. The dashed connection in the overview represents that distinction; it does not represent physical transport of the original NADH molecule through the membrane.

Why ATP Yield Is About 30–32, Not a Universal Constant

A common eukaryotic teaching estimate combines:

• 2 net ATP from glycolysis.
• 2 ATP/GTP equivalents from the cycle.
• About 26–28 ATP from oxidative phosphorylation.

The resulting about 30–32 ATP per glucose depends on assumptions about carrier shuttles, coupling and transport costs. Proton leak and cellular conditions also affect realized yield. Different textbook conventions may report different totals; state the model rather than treating any one number as a measured constant for every cell.

This overview concerns aerobic eukaryotic respiration. Bacteria lack mitochondria and use different compartment arrangements; see the bacterial cell diagram before adapting a mitochondrial layout to a prokaryote.

Respiration, Breathing and Photosynthesis

Breathing moves air. Gas exchange supplies oxygen and removes carbon dioxide. Cellular respiration is intracellular metabolism. The respiratory system diagram explains the airways and gas-exchange structures that support oxygen delivery in humans.

Plants also carry out cellular respiration, including in the light. Photosynthesis captures light energy and fixes carbon; respiration releases usable energy through the oxidation of organic molecules. The pathways are related, but they are not simply the same set of reactions running backward. Compare the photosynthesis diagram for chloroplast compartments and carrier connections.

Reading Check

A useful cellular respiration diagram lets a reader answer four questions: Where does each stage occur? Where does carbon go? How do electrons reach oxygen? Which ATP figures are net yields and estimates?

If any answer depends on guessing an unlabeled arrow, refine the figure. Open the cellular respiration diagram generator, specify the organism and teaching level, then review the compartments, carrier arrows and ATP assumptions before using the result. Generation requires an account and available credits.

References

1. OpenStax Biology 2e: Glycolysis — investment and payoff phases, net products.
2. OpenStax Biology 2e: Oxidation of Pyruvate and the Citric Acid Cycle — link reaction and cycle outputs.
3. OpenStax Biology 2e: Oxidative Phosphorylation — electron transport, chemiosmosis and reasons for ATP-yield variation.

Prepared by the AcaDraw product team; sources and schematic checked October 23, 2026. Independent expert review has not been completed. The schematic explains a conventional model and does not calculate experimental metabolic rates.