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Cellular Respiration Explorer

Explore how cells convert glucose and other substrates into ATP through glycolysis, the Krebs cycle, and the electron transport chain. Toggle between aerobic and anaerobic conditions, adjust temperature and substrate concentration, and compare the efficiency of different metabolic pathways.

Controls

Temperature37°C
0°C50°C
Oxygen Available

Aerobic conditions (O₂ present)

Glucose Concentration5.0 mM
0 mM20 mM

Results

Aerobic Respiration

Glucose at 37°C, 5.0 mM

Overall Reaction

C6H12O6+6O2→6CO2+6H2O+ATP\mathrm{C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP}

ATP Yield Breakdown

Glycolysis+2 ATP, 2 NADH
Pyruvate Oxidation0 ATP, 2 NADH, 2 CO₂
Krebs Cycle+2 ATP, 6 NADH, 2 FADH₂, 4 CO₂
Electron Transport+28 ATP
Total ATP32 ATP

32

Total ATP

34.0%

Efficiency

1.00

RQ (CO₂/O₂)

100%

Enzyme Activity

Gas Exchange (relative rate)

O₂ Consumption4.29 unitsCO₂ Production4.29 units

Respiratory Quotient

RQ=CO2 producedO2 consumed=1.00\mathrm{RQ} = \frac{\mathrm{CO_2\ produced}}{\mathrm{O_2\ consumed}} = 1.00

RQ = 1.0 indicates pure carbohydrate oxidation

ATP Yield by Stage

GlycolysisPyruvate OxidationKrebs CycleElectron Transport

Temperature vs Respiration Rate

Enzyme activity follows a bell curve. Below optimal, reaction rates increase with temperature (Q₁₀ effect). Above optimal, proteins denature rapidly.

Aerobic vs Anaerobic Comparison

Aerobic (32 ATP)Anaerobic (2 ATP)

Reference Guide

Glycolysis

Glycolysis splits one glucose molecule into two pyruvate molecules in the cytoplasm. This is the universal first step of both aerobic and anaerobic respiration.

C6H12O6+2NAD++2ADP+2Pi→2C3H4O3+2NADH+2ATP\mathrm{C_6H_{12}O_6 + 2NAD^+ + 2ADP + 2P_i \rightarrow 2C_3H_4O_3 + 2NADH + 2ATP}
  • Investment phase uses 2 ATP to phosphorylate glucose
  • Payoff phase generates 4 ATP and 2 NADH
  • Net yield is 2 ATP, 2 NADH, and 2 pyruvate per glucose

Glycolysis does not require oxygen, which is why it can proceed under both aerobic and anaerobic conditions.

Krebs Cycle (Citric Acid Cycle)

The Krebs cycle occurs in the mitochondrial matrix. Acetyl-CoA (from pyruvate oxidation) enters the cycle and is fully oxidized to CO₂, generating electron carriers.

Acetyl-CoA+3NAD++FAD+GDP+Pi→2CO2+3NADH+FADH2+GTP\mathrm{Acetyl\text{-}CoA + 3NAD^+ + FAD + GDP + P_i \rightarrow 2CO_2 + 3NADH + FADH_2 + GTP}
  • Per glucose: 2 turns produce 6 NADH, 2 FADH₂, and 2 GTP (equivalent to 2 ATP)
  • Releases 4 CO₂ per glucose (plus 2 from pyruvate oxidation = 6 total)
  • The cycle regenerates oxaloacetate as the starting molecule

Electron Transport Chain

The ETC is embedded in the inner mitochondrial membrane. NADH and FADH₂ donate electrons to the chain, which pumps H⁺ ions to create a proton gradient. ATP synthase uses this gradient to produce ATP (oxidative phosphorylation).

NADH→2.5 ATP;FADH2→1.5 ATP\mathrm{NADH \rightarrow 2.5\ ATP \quad;\quad FADH_2 \rightarrow 1.5\ ATP}
  • 10 NADH + 2 FADH₂ per glucose yield approximately 28 ATP
  • Oxygen is the final electron acceptor, forming water
  • Without oxygen, the ETC stops and the cell must rely on fermentation

Aerobic vs Anaerobic Respiration

Aerobic respiration produces up to 32 ATP per glucose (~34% efficiency), while anaerobic fermentation yields only 2 ATP (~2% efficiency). However, fermentation is faster and does not require oxygen.

Efficiency=ATP×30.5 kJ/mol2870 kJ/mol×100%\text{Efficiency} = \frac{\text{ATP} \times 30.5\ \text{kJ/mol}}{2870\ \text{kJ/mol}} \times 100\%
  • Lactic acid fermentation (muscles, bacteria) regenerates NAD⁺ by reducing pyruvate to lactate
  • Alcoholic fermentation (yeast) converts pyruvate to ethanol and CO₂
  • The Respiratory Quotient (RQ = CO₂/O₂) indicates which substrate is being metabolized: glucose = 1.0, fat = 0.7, protein = 0.8