Edexcel A Level (IAL) Biology -7.6 Respiratory Quotient- Study Notes- New Syllabus
Edexcel A Level (IAL) Biology -7.6 Respiratory Quotient- Study Notes- New syllabus
Edexcel A Level (IAL) Biology -7.6 Respiratory Quotient- Study Notes -Edexcel A level Biology – per latest Syllabus.
Key Concepts:
- 7.6 understand what is meant by the term respiratory quotient (RQ)
Respiratory Quotient (RQ)
🌱 Introduction
The respiratory quotient helps identify which respiratory substrate (carbohydrate, fat or protein) an organism is using. It is calculated from the volumes of gases exchanged during respiration.
What is Respiratory Quotient?
Respiratory Quotient (RQ) is defined as:
\[ RQ = \frac{CO_2 \text{ produced}}{O_2 \text{ consumed}} \]
It shows the relative amount of CO₂ released compared to oxygen taken in during respiration.
Why RQ Is Useful
- Indicates which substrate is being respired.
- Shows whether respiration is aerobic or anaerobic.
- Useful in studies of exercise, starvation and metabolic stress.
Typical RQ Values
| Substrate | RQ Value | Meaning |
|---|---|---|
| Carbohydrates | 1.0 | Equal CO₂ produced and O₂ consumed |
| Fats | 0.7 | More O₂ needed to oxidise fats |
| Proteins | 0.8–0.9 | Intermediate value |
| Anaerobic respiration | >1 | CO₂ release exceeds O₂ use |
📌 Key Points to Remember
- High RQ (>1) usually signals anaerobic respiration.
- Values reveal which substrate is the main energy source.
- Measured using respirometers or metabolic equipment.
🧠 Quick Recap
RQ = CO₂ produced ÷ O₂ consumed.
Carbs ≈ 1, fats ≈ 0.7, proteins ≈ 0.8.
RQ > 1 suggests anaerobic conditions.
Helps determine the substrate being respired.
RQ = CO₂ produced ÷ O₂ consumed.
Carbs ≈ 1, fats ≈ 0.7, proteins ≈ 0.8.
RQ > 1 suggests anaerobic conditions.
Helps determine the substrate being respired.