Define Respiratory Quotient

Learn about respiratory quotient and its significance in metabolism. Discover how RQ values can reflect different fuel sources and metabolic states. Explore examples, case studies, and statistics.

What is Respiratory Quotient?

Respiratory quotient (RQ) is a ratio used in biochemistry to describe the amount of carbon dioxide produced compared to the amount of oxygen consumed during cellular respiration. It provides valuable insights into the type of fuel being used for energy production and the efficiency of metabolism.

Calculating Respiratory Quotient

The formula to calculate respiratory quotient is RQ = CO2 produced / O2 consumed. Different fuels have different RQ values, for example, carbohydrates have an RQ of 1, fats have an RQ of 0.7, and proteins have an RQ of around 0.9.

Importance of Respiratory Quotient

Respiratory quotient can help in determining the metabolic state of an organism. A high RQ indicates carbohydrate metabolism, while a low RQ suggests fat metabolism. It can also be used to monitor the effects of exercise, diet, and various diseases on metabolism.

Examples of Respiratory Quotient

An example of a high RQ scenario is when a person is running, as carbohydrates are the primary fuel used for quick energy. On the other hand, during fasting or low-intensity activities, the RQ will be lower due to fat being the predominant fuel source.

Case Studies

A study conducted on athletes found that their RQ values changed based on the type and intensity of exercise they were performing. This highlighted the adaptability of metabolism to different energy demands.


Research has shown that individuals with metabolic disorders such as diabetes have altered RQ values compared to healthy individuals. Monitoring RQ can aid in early detection and management of such conditions.

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