1. Fermentation: Anaerobic respiration taking place in bacteria and fungi, in which glucose is incompletely oxidized into alcohol and CO2 or organic acid is called fermentation.
2. Oxidative break-down of pyruvic acid: Pyruvic acid formed as an end product of glycolysis enters mitochondria and in the matrix region of mitochondria, it is completely oxidized into CO2 and H2O in the presence of oxygen. This is called an oxidative breakdown of pyruvic acid. Before entry into mitochondria, pyruvic acid is converted into Acetyl Coenzyme-A by decarboxylation and dehydrogenase enzyme. This complex reaction is catalyzed by five co-factors. These are Coenzyme A; NAD+ ; Mg++; Thymine pyrophosphate (TPP) and Lipoic acid. Acetyl Coenzyme – A formed in this reaction acts as a connecting link between glycolysis and Krebs cycle.
3. Respiratory Quotient: The ratio of the volume of CO2 released in respiration to the volume of O2 used is called respiratory quotient.
The value of R.Q. of different respiratory substrates is as follows:
R.Q. of carbohydrate = 1.0
R.Q. of fats = 0.7
R.Q. of proteins = 0.8
R.Q. of organic acids = 1.33
R.Q. of succulents = zero Anaerobic respiration
R.Q. = infinite (∝).
4. Chemiosmotic theory of Mitchell: This theory was proposed by Mitchell to explain ATP formation during respiration and photosynthetic process. According to this theory, transport of positively charged protons (Hydrogen ions) across the membrane of mitochondria or chloroplasts takes place through the enzymes involved in these processes via an electron transport system. Due to this, the electrochemical gradient is created on two sides of the membrane.
