All Jharkhand Competitive Exam JSSC, JPSC, Current Affairs, SSC CGL, K-12, NEET-Medical (Botany+Zoology), CSIR-NET(Life Science)

Monday, February 1, 2021

Respiration & Energy Transfer (Anaerobic Respiration) - NEET


Respiration & Energy Transfer (Anaerobic Respiration) 

  • Maintenance of life requires a continuous supply of energy.
  • Respiration fulfills the continuous need for energy.

  • Respiration is a catabolic process wherein complex organic substrate is oxidized to simple components to generate biological energy.

Cellular respiration occurs in two different ways like 1.) anaerobic and 2.) aerobic respiration.

  • It is cellular respiration that does not involve oxygen at all.
  • It is completed through steps like glycolysis and conversion of glycolytic product to any suitable product like lactic acid, ethanol, etc.


  • It involves the breakdown of a glucose molecule into two pyruvic acid molecules.
  • This is a common step in anaerobic as well as aerobic respiration.
  • It is completed in two phases as preparatory phase and the pay-off phase.
  • The overall process of glycolysis is completed in ten steps.

1.) Preparatory phase:

  • The first five steps constitute the preparatory phase through which glucose is phosphorylated twice at the cost of two ATP molecules and a fructose 1,6-biphosphate is formed.

  • This molecule is split to form: 1.) a molecule of glyceraldehyde 3-phosphate & 2.) a molecule of dihydroxyacetone phosphate.

  • Both of these molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.

  • Dihydroxyacetone phosphate is isomerized to the second molecule of glyceraldehyde-3-phosphate.

  • Thus, two molecules of glyceraldehyde-3-phosphate are formed, and here, the preparatory phase of glycolysis ends.

2.) Pay-off phase:

  • Both the molecules of glyceraldehyde-3-phosphate are converted to two molecules of 1, 3-biphosphoglycerate by oxidation and phosphorylation.

  • Phosphorylation is brought about with the help of inorganic phosphate (Pi) and not ATP.

  • Both molecules of 1, 3-biphosphoglycerate are converted into two molecules of pyruvic acid through series of reactions accompanied by the release of energy.

  • This released energy is used to produce ATP (4 molecules) by substrate-level phosphorylation.

  • 2 ATP/glucose is the net outcome.

  • Energy is also converted by the formation of 2-NADH molecules.

B.) Lactic Acid Fermentation (In Muscle):

  • In muscles, the NADH+H ion produced during glycolysis is reoxidized to NAD+ by donating one proton and two electrons to pyruvic acid which yields lactic acid. 


  • In this reaction pyruvate is converted into a 3-carbon molecule called lactic acid.


  •  No production of carbon dioxide (CO2).


  • The only benefit is serves is that it allows glycolysis to continue with the small gain of ATP generated. 


  • Skeletal muscles usually derive their energy by anaerobic respiration. 


  •  After vigorous exercise lactic acid accumulates, leading to muscle fatigue. 


  • During rest, however, the lactic acid is reconvereted to pyruvic acid and is channeled back into the aerobic respiration pathway.

C.) Alcoholic Fermentation (In Yeast):

  • In yeast, the pyruvate is decarboxylated to acetaldehyde.


  • The acetaldehyde is then reduced by NADH+H ion to ethanol.


  • Carbon dioxide (CO2) is also produced in this process.


  • Accumulation of ethanol by fermentation in a culture of yeast may stop further multiplication and lead to the death of cells.


  • In the presence of oxygen (O2) however, yeast can respire aerobically.


  • Examples of food produced are alcoholic drinks, bread, cakes, etc.








Post a Comment

Unordered List

Search This Blog

Powered by Blogger.

About Me

My photo
Education marks proper humanity.

Text Widget

Featured Posts

Popular Posts

Blog Archive