Respiration in Plants

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KNOWLEDGE CORNER

E.g. When used as a substrate, fatty acids breakdown

to acetyl CoA before entering the respiratory pathway.

(NEET II 2016) But when the organism needs to synthesize

fatty acids, acetyl CoA is withdrawn from the respiratory

pathway to form fatty acids.

Similarly, during breakdown and synthesis of protein,

respiratory intermediates are involved

RËSPÏRÅTØRÝ QÜØTÏËÑT (RQ) ØR RËSPÏRÅTØRÝ RÅTÏØ



It is the ratio of the volume of CO2 evolved to the volume of O2 consumed

in respiration.

RQ =

Volume of CO2 evolved

(AIPMT 1990)

Volume of O2 consumed



RQ depends upon the type of respiratory substrate.



RQ for carbohydrates = 1 , because equal amounts of CO2 and O2 are

evolved and consumed, respectively.

C6H12O6 + 6O2 ® 6CO2 + 6H2O + energy

RQ =

6 CO2

= 1.0

6 O2



RQ for fats = < 1. Calculations for a fatty acid, (e.g. tripalmitin) are shown:

2 (C51 H98 O6) + 145O2 ® 102 CO2 + 98 H2O + energy

RQ =

102 CO2

= 0.7

(NEET 2019)

145 O2



RQ for proteins = 0.9.



In living organisms, respiratory substrates are often more than one. Pure

proteins or fats are never used as respiratory substrates.