Aerobic and anaerobic respiration – Differentiator

Aerobic and anaerobic respiration are types of cellular respiration, that is, ways that some cells have to obtain energy from what they consume. They differ in that oxygen is required for aerobic respiration, while oxygen is absent in anaerobic respiration.

Also, more energy is produced in aerobic respiration compared to anaerobic respiration; however, it has more chemical steps, so it takes longer to perform.

Aerobic and anaerobic respiration share in the first phase glycolysis or glycolysis, a chain of chemical reactions that transform glucose into smaller molecules.





definition Cellular process of glucose transformation to obtain energy with the participation of oxygen. Process of obtaining energy that some cells use in the absence of oxygen.
Electron acceptor oxygen
  • Nitrate
  • Sulphate
  • Carbon dioxide
  • Metal ions
Stages or phases
  1. glycolysis
  2. Citric acid cycle
  3. Oxidative phosphorylation
  1. glycolysis
  2. Fermentation:
    a) lactic
    b) ethanolic


Carbon dioxide

32 ATP/glucose

lactic acid

Ethyl alcohol


2 ATP/glucose


Liver cells

Kidney cells

Except for bread

Erythrocytes or red blood cells



Aerobic respiration

Aerobic cellular respiration is the process that transforms chemical energy from food into ATP in the presence of oxygen. Oxygen receives electrons at the end of a chain of chemical reactions generating water, carbon dioxide and energy.

First phase of aerobic respiration: glycolysis

The first step in aerobic respiration is the breakdown of glucose or glycolysis. This occurs in the cytoplasm of cells. As a result of glycolysis, two ATP and two electrons are obtained in the form of NADH and two molecules of pyruvate:

scheme of glycolysis

Second phase of aerobic respiration: citric acid cycle

The second step of aerobic respiration is the citric acid cycle or Krebs cycle. This is a series of eight chemical reactions that take place in the mitochondria of eukaryotic cells.

A pyruvate from glycolysis enters the cycle and results in three NADH, three carbon dioxide, one GTP and one FADH2:

scheme of the citric acid cycle

Third phase of aerobic respiration: oxidative phosphorylation

The third and final step of aerobic respiration is the process of oxidative phosphorylation. This process is carried out in the electron transport chain, a set of proteins in the mitochondrial membrane that transfer NADH electrons from the Krebs cycle.

The end result of aerobic respiration is 32 ATP per glucose molecule:

scheme of the production of ATP in the mitochondrion by oxidative phosphorylation

Anaerobic respiration

Anaerobic cellular respiration is the way prokaryotic cells and some eukaryotic cells obtain energy from glucose, without the need for oxygen. It is carried out in the cytoplasm of the cell.

Anaerobic respiration is used for energy production in cells that do not have mitochondria, such as bacteria, archaea, and red blood cells. In fast muscle contraction, muscle cells can resort to anaerobic respiration, producing lactic acid.

First phase of anaerobic respiration: glycolysis

Anaerobic respiration begins with glycolysis, the process of breaking down glucose, just as it does in aerobic respiration. In this step two energy molecules or ATP are produced.

Second phase of anaerobic respiration: fermentation

The next step can be fermentation, of which there are two types:

  1. Lactic fermentation: where pyruvate is transformed into lactate, as happens in yogurt bacteria.
  2. Ethanol fermentation: in this case pyruvate gives rise to ethanol and carbon dioxide, a process carried out by wine and beer yeasts.

type of fermentation

Some animals can switch to anaerobic respiration, such as carp or goldfish. When the surface of lakes freezes in winter, the oxygen in the water decreases. These fish, which normally exhibit aerobic respiration, can survive thanks to their ability to maintain anaerobic respiration.

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