## **Core Concept**
The respiratory quotient (RQ) is a measure used in physiology to describe the ratio of carbon dioxide (CO2) produced to oxygen (O2) consumed during the process of cellular respiration. It varies depending on the type of food being metabolized. For carbohydrates, the general equation for cellular respiration can be simplified.

## **Why the Correct Answer is Right**
The complete oxidation of a typical carbohydrate, such as glucose, can be represented by the equation: C6H12O6 + 6O2 → 6CO2 + 6H2O. From this equation, it is evident that 6 molecules of CO2 are produced for every 6 molecules of O2 consumed. Therefore, the respiratory quotient (RQ) for carbohydrate metabolism is 6CO2 / 6O2 = 1. This indicates that for carbohydrates, the amount of CO2 produced equals the amount of O2 consumed.

## **Why Each Wrong Option is Incorrect**
- **Option A:** . This option suggests an RQ value less than 1, which would be more indicative of fat metabolism. During fat metabolism, more O2 is consumed than CO2 produced, leading to an RQ value of approximately 0.7.
- **Option B:** . This option implies an RQ value that does not accurately reflect the metabolism of carbohydrates, proteins, or fats specifically.
- **Option D:** . This option suggests an RQ value greater than 1, which can occur during the metabolism of certain organic acids or during ketosis, not typical for carbohydrate metabolism.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the RQ can help in assessing the type of substrate being utilized by the body for energy. For example, an RQ of 1 indicates carbohydrate metabolism, while an RQ of approximately 0.7 indicates fat metabolism. This concept can be crucial in critical care settings for managing patients' nutritional needs.

## **Correct Answer:** .