The three stages of anaerobic respiration

Generally, cellular respiration can be divided into two types: aerobic respiration and anaerobic respiration. The animals, plants and human bodies we often see all perform aerobic respiration. Without the participation of oxygen, we will not be able to ensure the normal functioning of living organisms. The fermentation process we usually refer to is anaerobic respiration. Anaerobic respiration means that cells can carry out normal respiratory metabolism even when isolated from oxygen, so it is also called anaerobic respiration.

Basic content

Anaerobic respiration refers to the incomplete oxidation of organic matter by biological cells. There is no involvement of oxygen molecules in this process, and the incomplete oxidation products after oxidation are mainly alcohol. In higher plants, anaerobic respiration is often called fermentation. This process does not involve molecular oxygen. When the incomplete oxidation product after oxidation is alcohol, it is called alcoholic fermentation; if it is lactic acid, it is called lactic acid fermentation. However, in the broad sense of "anaerobic respiration", these two concepts are usually not distinguished.

Aerobic respiration

Depending on the final electron acceptor, anaerobic respiration can be divided into nitrate respiration, sulfate respiration, sulfur respiration, carbonate respiration and fumarate respiration. The most typical of these is nitrate respiration.

In biological oxidation or energy metabolism, fermentation refers to a type of inefficient energy-generating reaction in which the reducing power [H] generated by deoxygenation of the substrate under anaerobic conditions is directly transferred to an endogenous oxidative intermediate metabolite without being transferred through respiration. In microorganisms, anaerobic respiration is often called fermentation, which refers to the incomplete oxidation of organic matter by living cells.

Anaerobic respiration and fermentation diagram

Under hypoxic conditions, they can only carry out anaerobic respiration to temporarily maintain their life activities. Anaerobic respiration will eventually harm plants, partly because organic matter is incompletely oxidized and produces less energy. Then, due to the Pasteur effect, the rate of glycolysis is accelerated to compensate for the low ATP yield. This in turn causes the accumulation of incomplete oxidation products, which are toxic to cells. In addition, it also accelerates the consumption of sugar, posing the risk of exhausting respiratory substances.

Except for beet roots, potato tubers, corn endosperm and carrot leaves, the product of anaerobic respiration in plants is generally alcohol.

Reactive

C6H12O6 + enzyme → 2C3H6O3 (lactic acid) + small amount of energy

C6H12O6 + enzyme → 2C2H5OH (alcohol) + 2CO2 + small amount of energy

Key Features

Anaerobic respiration is a form of cellular respiration.

According to the different classification methods of the final electron acceptors, cellular respiration is divided into three types: fermentation, aerobic respiration, and anaerobic respiration. Yeast brewing, homolactic fermentation and heterolactic fermentation all fall under the category of fermentation, not anaerobic respiration. Simply put, oxidation without the use of oxygen is not necessarily anaerobic respiration. But in the broad sense of "anaerobic respiration", these two concepts are usually not distinguished.