Aerobic and Anaerobic respiration – Class 11 | Chapter – 14 | Biology Short Notes Series PDF

Aerobic and Anaerobic respiration: Respiration is a biochemical process which is common in all living organisms. In this process, there is the movement of air in and out of the lungs. Respiration takes place in every living cell, all of the time and all cells need to respire in order to produce the energy that they require. There are two main types of respiration, aerobic and anaerobic.


Aerobic and Anaerobic respiration

Aerobic respiration

Aerobic respiration is a biological process in which food glucose is converted into energy in the presence of oxygen. The chemical equation of aerobic respiration is as given below-

Glucose (C6H12O6)  + Oxygen 6(O2) → Carbon-dioxide 6(CO2)  +  Water 6 (H2O) + Energy (ATP)

According to the above-given chemical equation, energy is released by splitting the glucose molecules with the help of oxygen gas. At the end of the chemical reaction, energy, water molecules, and carbon dioxide gas are released as the by-products or end products of the reactions.

The 2900 kJ of energy is released during the process of breaking the glucose molecule and in turn, this energy is used to produce ATP – Adenosine Triphosphate molecules which are used by the system for various purposes.

Aerobic respiration process takes place in all multicellular organisms including animals, plants and other living organisms.

Stages of Aerobic Respiration

Stages of Aerobic Respiration

The complete process of aerobic respiration occurs in four different  stages:


It is the primary step of aerobic respiration is glycolysis and takes place within the cytosol of the cell. During the glycolysis process, the glucose molecules are splitting and separated into two ATP and two NADH molecules, which are later used in the process of aerobic respiration.

Formation of Acetyl Coenzyme A

The second step in aerobic respiration is the formation of acetyl coenzyme A. In this process, pyruvate is oxidized in the mitochondria and  2-carbon acetyl group is produced. The newly produced 2-carbon acetyl group binds with coenzyme A, producing acetyl coenzyme A.

Citric Acid Cycle

The third step in aerobic respiration is the citric acid cycle, which is also called the Krebs cycle. In this stage of Aerobic respiration, the oxaloacetate combines with the acetyl-coenzyme A and produces citric acid. The citric acid cycle undergoes a series of reactions and produces 2 molecules of carbon dioxide, 1 molecule of ATP, and reduced forms of NADH and FADH.

Electron Transport Chain

This is the last step in aerobic respiration. In this phase, the large amounts of ATP molecules are produced by transferring the electrons from NADH and FADH. A single molecule of glucose creates a total of 34 ATP molecules

Anaerobic Respiration

  • Anaerobic respiration is the respiration which occurs in the absence of oxygen to produce the energy.
  • It occurs in yeast cells in which alcohol is produced.
  • It also occurs in muscles of our body when we do excess workout which causes the temporary lack of the oxygen for muscles.
  • Glucose  Ethanol + Carbon dioxide + Energy (In yeast cells).
  • The muscle cells then start doing anaerobic respiration and produce lactic acid.
  • Glucose  Lactic acid + Energy (in muscles).
  • There is partial breakdown of glucose.

Biology Quiz & Notes Physics Quiz & Notes Chemistry Quiz & Notes

Follow on Facebook

By Team Learning Mantras