Summary
Glucose plus oxygen yields carbon dioxide, water and energy released as ATP and heat.
In depth
The respiratory quotient (CO2/O2) is 1.0 for carbohydrate, about 0.7 for fat and 0.8 for protein. It shows which substrate is used. Glucose oxidation gives about 17 kJ per gram.
The equation shows conservation of matter: each glucose carbon becomes CO2. Oxygen atoms end in water. Heat is released as the energy is not all captured.
Remember: the equation summarises many steps.
The overall equation for aerobic respiration of glucose is C6H12O6 + 6 O2 gives 6 CO2 + 6 H2O + energy (about 2,870 kJ per mole of glucose, of which roughly 34 percent is stored as ATP). It summarises many steps.
The equation is balanced and shows that for each glucose, six O2 are used and six CO2 are produced, giving a respiratory quotient of 1. The water produced is called metabolic water, vital for desert animals such as camels and kangaroo rats.
Example: experiments with limewater or hydrogencarbonate indicator show CO2 production by germinating seeds.
Key idea: the equation is the reverse of photosynthesis, but the pathways differ.
Frequently asked questions
What is Respiratory Equation?
Glucose plus oxygen yields carbon dioxide, water and energy released as ATP and heat.
Which area of biology covers Respiratory Equation, and how advanced is it?
Respiratory Equation is one of the 53 topics in Metabolism & Bioenergetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Respiratory Quotient, Cellular Respiration, Aerobic and Anaerobic Respiration.
Can you give an example of Respiratory Equation?
RQ above 1 may indicate anaerobic respiration or fat synthesis.
What should I learn before Respiratory Equation?
Respiratory Equation is a Beginner topic, so no earlier topic is required. Other Beginner topics in Metabolism & Bioenergetics that pair well with it include Metabolism, Anabolism and Catabolism, ATP.
What topics are related to Respiratory Equation?
The closest topics to Respiratory Equation are Respiratory Quotient, Cellular Respiration, Aerobic and Anaerobic Respiration, Alcoholic Fermentation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Respiratory Equation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Respiratory Equation. To practise the whole of Metabolism & Bioenergetics, use the Metabolism & Bioenergetics quiz.
How is Respiratory Equation different from Respiratory Quotient?
Respiratory Equation: Glucose plus oxygen yields carbon dioxide, water and energy released as ATP and heat. Respiratory Quotient: The ratio of carbon dioxide produced to oxygen consumed, indicating which fuel is being used. Read both side by side and note what each one explains.
How should I study Respiratory Equation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Respiratory Quotient and explain the difference aloud. Finally, take the Metabolism & Bioenergetics quiz and come back to this page for any question you miss.