Question

Explain how cellular respiration (O2 consumption and CO2 production) is linked to ATP production. Is the coupling of these two processes perfect? Why or why not?

Answer 1

The primary function of cellular respiration is to generate ATP, which traps some of the chemical energy of food molecules in its high- energy bonds (adenosine triphosphate). The process of generation of ATP is via glycolysis and Krebs’s cycle finally through oxidative phosphorylation.

The overall balanced reaction of cellular respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP                   

Glucose + oxygen → carbon dioxide + water + energy        

In this reaction, glucose oxidized and oxygen reduced.      

Cellular respiration (O2 consumption and CO2 production) is linked to ATP production because it is different from cellular respiration as it involves metabolic activities using molecular oxygen such as Citric acid cycle and electron transport to synthesize energy in the form of ATP to perform respiration. CO2 is the output of the cellular respiration from mitochondria and expelled out of the body by carrying through hemoglobin in the form of carboxy- hemoglobin to the alveoli of lungs.

The coupling of these two processes such as O2 consumption and CO2 production inked to ATP production is perfect. Mitochondrial chemiosmosis –cellular respiration (through Fernadez Moran inner mitochondrial oxysomes particles) during cellular respiration obtain energy from chemical enzymatic breakdown of the organic food molecules (glucose, pyruvate, acetylcoA) to produce ATP in the presence of O2 consumption. During electron transport, the final electron acceptor is oxygen for oxidative phosphorylation via energy producing molecules such as NADH (3 ATP), FADH2 (2ATP) and ATP. Therefore, it is going to "oxygen" that accepting electrons at the end of the electron transport chain to generate ATP via mitochondrial respiratory complex-I to V. Every 3 protons used to produce one ATP molecule. Inner membrane possess small protein channels known as porins in mitochondria & these channels promote the movement of any small molecules such as ATP through them

However, the coupling is perfect between the O2 consumption and CO2 production for ATP production but whole-organism oxygen consumption is mainly related to rate of substrate oxidation & it cannot be accurate measurement for ATP production due to variable P/O ratio occurs.