Cellular Respiration Calculator
Calculate oxygen consumption, CO2 production, and RQ (respiratory quotient) for aerobic respiration. Find energy yield from different substrates: glucose, fat, and protein.
🧬 Cell Biology📐 RQ = CO2 produced / O2 consumed🧬 Biology
Substrate
Moles of substrate consumed
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Cellular Respiration Calculator | — | RQ = CO2 produced / O2 consumed | dimensionless |
Step-by-Step Examples
Example 1
Glucose Combustion
1 mol glucose completely oxidized.
- C6H12O6 + 6O2 to 6CO2 + 6H2O + 686 kcal
- RQ = 6 CO2 / 6 O2 = 1.0
- 686 kcal / mol = 30-32 ATP
✓ RQ = 1.0 for carbohydrates
Example 2
Fat Oxidation
Palmitate (C16) oxidation.
- C16H32O2 + 23O2 to 16CO2 + 16H2O
- RQ = 16/23 = 0.70
- Fats consume more O2 per carbon (less oxidized)
✓ RQ = 0.70 for fat (uses more O2)
Example 3
Mixed Diet
Measured RQ = 0.85 at rest.
- RQ between 0.7 and 1.0 = mixed substrate use
- RQ 0.85 typical of mixed carb + fat combustion
- Exercise: RQ increases toward 1.0 as carbs predominate
✓ RQ 0.85: burning mixed carbohydrate and fat
Real-World Applications
Exercise Physiology
RQ rises during intense exercise (carb-dependent) and falls during recovery (fat oxidation).
Intensive Care
Indirect calorimetry measures O2 consumed and CO2 produced at bedside to assess metabolic rate and substrate utilization.
Metabolic Research
RQ tells which fuel is being burned without invasive sampling. Used in metabolic chambers.
Neonatology
Premature infants measured for O2 consumption to assess metabolic status and caloric needs.
Common Mistakes to Avoid
⚠️
RQ near 1.0 means carbohydrate burning
Pure carbohydrate: RQ = 1.0. Pure fat: RQ = 0.70. Pure protein: ~0.80. Measure RQ to estimate fuel mix without metabolic sampling.
⚠️
Photosynthesis has RQ less than 1
Plants building carbohydrates from CO2: CO2 fixed, O2 produced. RQ for overall net photosynthesis is inverse of respiration.
⚠️
RQ above 1 indicates lipogenesis
If RQ > 1.0: carbohydrate being converted to fat (de novo lipogenesis). Excess carb calories are stored as fat.
Frequently Asked Questions
What is respiratory quotient? ▾
RQ = CO2 produced / O2 consumed. Reflects the type of fuel being burned. Pure carbohydrate: 1.0. Pure fat: 0.70. Mixed: 0.78-0.90 typically.
What is indirect calorimetry? ▾
Measuring O2 consumption and CO2 production to calculate metabolic rate and substrate usage without direct calorie measurement. Used in sports science and intensive care.
What is VO2max? ▾
Maximum rate of oxygen consumption during intense exercise. Measure of aerobic fitness. Higher VO2max = greater aerobic capacity. Elite athletes: 70-90 ml O2/kg/min.
Why do fats have lower RQ? ▾
Fats are more reduced (lower O/C ratio) than carbohydrates. More O2 is needed to fully oxidize each carbon. C16 fatty acid: 23 O2 for 16 CO2 gives RQ = 0.70.
How does diet affect RQ? ▾
High-carb diet: RQ near 0.90. Ketogenic diet (high fat): RQ near 0.70-0.75. Fasting: initially 0.85 (mixed), then decreasing as fat mobilization increases.