Respiration In Plant

 Respiration In Plant

 

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some IMP points 

Aerobic:-

(1)This accounts for complete oxidation (end products are

      inorganic) of food (glucose) to CO2 and H2O.

(2) Its an intermolecular respiration.

(3) 36 or 38 molecules of ATP gain for each molecule of Glucose

(4) NADH is oxidised to NAD+ vigorously

(5)O2 remove hydrogen from the system and acts as the final hydrogen acceptor

(6) ReactionC6H12O6+6O2+6H2O ¾® 6CO2 + 12H2O + 686 kcal     

 

Anaerobic/Fermentation :-

(1)This accounts for only a partial breakdown of glucose

to either lactic acid or ethanol and CO  

(2) Its an intramolecular respiration 

(3) There is gain of only two molecules of ATP for each molecule of glucose 

(4) NADH is oxidised to NAD+ rather slowly. 

(5)O2 is absent. Hydrogen acceptor in the system is either acetaldehyde (during alcoholic fermentation) or Pyruvate (during lactic acid fermentation) 

(6)Reaction C6H12O6 ¾® 2CH3CH2OH + 2CO2 + less than 7% of energy of glucose 'or' C6H12O6 ¾® 2C3H6O3 + less than 7% of energy of glucose    

 

Krebs cycle

(i) Named after the scientist Hans Krebs who first elucidated it. It is also called TCA (tri carboxylic acid) cycle or CA (citric acid) cycle.

(ii) Krebs cycle occurs inside mitochondrial matrix of eukaryotic cells and cytoplasm of prokaryotic cells.

(iii) One turn of Krebs cycle involve four dehydrogenation , two decarboxylation and one substrate level phosphorylation.

(iv) OAA is considered as the first member of the cycle.

(v) All enzymes of Krebs cycle are located inside mitochondrial matrix except succinate dehydrogenase (Marker enzyme), which is located in inner membrane of mitochondria  

 

Amphibolic pathway

(i) Glucose is the favoured substrate for respiration. All carbohydrates are usually first converted into glucose before they are used for respiration. Other substrates can also be respired, but then they do not enter the respiratory pathway at the first step.

(ii) Fats would need to be broken down into glycerol and fatty acids first. If fatty acids were to be respired they would first be degraded to acetyl CoA and enter the pathway. Glycerol would enter the pathway after being converted to PGAL.

(iii) The proteins would be degraded by proteases and the individual amino acids (after deamination) depending on their structure would enter the pathway at some stage within the Krebs cycle or even as pyruvate or acetyl CoA.

(iv) Since respiration involves breakdown of substrates, the respiratory process has traditionally been considered a catabolic process and the respiratory pathway as a catabolic pathway. Fatty acids would be broken down to acetyl CoA before entering the respiratory pathway when it is used as a substrate. But when the organism needs to synthesise fatty acids, acetyl CoA would be withdrawn from the respiratory pathway for it. Hence, the respiratory pathway comes into the picture both during breakdown and synthesis of fatty acids. Similarly, during breakdown and synthesis of protein too, respiratory intermediates form the link. Breaking down  processes within the living organism is catabolism, and synthesis is anabolism. Because the respiratory
pathway is involved in both anabolism and catabolism, it would hence be better to consider the respiratory pathway as an amphibolic pathway rather than as a catabolic one.