The respiratory quotient is the ratio of carbon dioxide produced to oxygen consumed during respiration over a period of time. It can be used to calculate oxygen consumption and carbon dioxide production and reflects the metabolic rate of an organism. The RQ of most animals at rest is 0.8-0.9 and for humans is 0.85. The RQ varies depending on the substrate being oxidized, with glucose having an RQ of 1, fat of 0.696, and proteins of 0.8. The type of respiration, aerobic or anaerobic, can also be determined from the RQ.

1. Respiratory Quotient

2. Respiratory Quotient
 With in a specific time , the ratio of the quantity of carbon dioxide produced to the
quantity of oxygen consumed is known as respiratory quotient.
 𝑅𝑒𝑠𝑝𝑖𝑟𝑎𝑡𝑜𝑟𝑦 𝑞𝑢𝑜𝑡𝑖𝑒𝑛𝑡:
𝐶𝑂2 𝑅𝐸𝐿𝐸𝐴𝑆𝐸𝐷
𝑂2 𝐶𝑂𝑁𝑆𝑈𝑀𝐸𝐷
 Functions:
 Calculate the quantity of oxygen consumed and quantity of carbon dioxide
released by applying the respiratory quotient.
 Represent the oxidation reaction of various kind of food or substrate.
 Reflect the metabolic rate of an organism.

3.  The respiratory quotient of most animals at rest is in the range of 0.8 to 0.9.
 The human respiratory quotient is about 0.85.
 The respiratory quotient of fats may vary depending on the type of fat.
 It is necessary to view such data with caution .
 If a mixture of substrate is being used then figure will be different from the given
table on next slide.
 For example :an respiratory quotient of 0.8 could point to both protein and fat
being used.

4. Substrate Respiratory quotient
Glucose 1
Fat 0.696
Proteins 0.8

5. Respiratory Quotient Represents types of
respiration
 If Respiratory Quotient is smaller than 1 then it will be aerobic respiration.
 If Respiratory Quotient is equal to 1 then it will be aerobic respiration.
 If Respiratory Quotient is greater then 1 then it will be anaerobic respiration.
 Low value of respiratory quotient indicates that:
 Aerobic respiration is being carried out.
 Plants absorb CO2 to carry out photosynthesis.
 Animals utilizes carbon element to manufacture calcareous shell.

6.  High value of Respiratory quotient indicates:
 Anaerobic respiration is being carried out.
 Conversion of carbohydrates into fats for example for hibernation.
 Process of large quantity of food for storage.
