Aerobic Vs Anaerobic Respiration Overview

Aerobic Respiration Definition

In order for chemical energy to be converted into ATPs, a combination of metabolic processes known as aerobic respiration must occur in the presence of oxygen in a cell.

• With the exception of a few primordial prokaryotes, all plants, animals, and birds, including humans, participate in aerobic respiration.
• Oxygen functions as an electron acceptor in aerobic respiration, accelerating the production of ATPs.
• More ATPs are produced because the oxygen double bond has greater energy than other bonds.
• Pyruvate is best degraded by this route, which involves glycolysis before entering the mitochondria to undergo complete oxidation during the Kreb’s cycle.
• In the process of aerobic respiration, reactants from proteins and lipids are also used to break down carbohydrates.
• Aerobic respiration makes carbon dioxide gas and water as by-products. It also makes the energy needed to add a third phosphate group to ADP and make ATP.
• Through the use of oxygen and protons in an electron transport chain, other energy-rich molecules like NADH and FADH2 are transformed into ATP.
• The majority of ATPs are produced during aerobic respiration, in which protons are pumped out of the membrane with the energy of an oxygen molecule.
• Protons move through a cell, creating a potential that is needed to start ATP synthase, which makes ATP from ADP and a phosphate group.
• At the completion of aerobic respiration, 38 ATPs should be created in total.
• Still, some energy is lost because the membrane leaks and it costs energy to move pyruvate across the cell. This means that only 29–30 ATPs can be made.
• The enzymes needed for aerobic respiration are found in the mitochondria of eukaryotic cells. This means that carbohydrate molecules can be fully oxidised through aerobic respiration.

Anaerobic Respiration Definition

The high-energy electron acceptor in anaerobic respiration is neither oxygen nor pyruvate derivatives.

• Sulfate ions (SO4-) and nitrate ions (NO3-) are two molecules that can act as electron acceptors in anaerobic respiration.
• Methane is a by-product of some archaea, known as methanogens, which employ carbon dioxide as an electron acceptor.
• Similar to the previous group, another kind of purple sulphur bacterium employs sulphate as an electron acceptor and generates hydrogen sulphide as a byproduct.
• These organisms use anaerobic pathways to turn chemical fuels into energy because they live in places with low levels of oxygen.
• In anaerobic respiration, just like in aerobic respiration, molecules join the electron transport chain to send electrons to the last electron acceptor.
• Because the terminal electron acceptors in anaerobic respiration get a lower reduction potential than oxygen molecules, less energy is generated.
• However, anaerobic respiration is essential for the carbon, nitrogen, and sulphur biogeochemical cycles.
• Nitrogen gas is a consequence of anaerobic respiration, which uses nitrate as an electron acceptor and is the only means through which fixed nitrogen enters the environment.
• Another kind of anaerobic respiration is fermentation, which does not include the citric acid cycle and uses glycolysis as the sole energy source.
• Additionally, during fermentation, NADH, a molecule with a lot of energy, is not used.
• Many different habitats, including freshwater, soil, and deep-sea surfaces, support anaerobic respiration. Some microorganisms that live in oxygenated environments also use anaerobic respiration because oxygen has a hard time getting through their surface.
• Both anaerobic respiration and fermentation take place in the cytoplasm of prokaryotic cells.
• During fast relaxation and contraction, muscle cells undergo anaerobic respiration and fermentation.
• Only two ATPs are added overall during fermentation for every glucose molecule.

Examples of Aerobic Respiration

Respiration in humans

• The process of aerobic respiration happens in human cells. This is how the body gets the energy it needs from glucose
• The process starts in the cytoplasm of the cell, and then the products are moved to the mitochondria, where more reactions take place.
• The red blood cells store the oxygen that is taken up by the lungs. The cells that need energy are subsequently given oxygen.
• After that, the glucose is oxidized, which gives off carbon dioxide gas and energy.
• In humans, cellular respiration is the process by which the main metabolic pathways for burning carbs to make energy are carried out.

Examples of Anaerobic Respiration

Lactic acid production in muscles

• When we work out hard, our muscles use more glycolysis than the body can transmit to the electron transport chain because they can’t absorb enough oxygen.
• As a consequence, our muscles are not getting enough oxygen, which causes anaerobic respiration.
• Because of this, aerobic respiration is replaced by anaerobic respiration, which leads to the production of lactic acid.
• Lactic acid fermentation is a kind of anaerobic respiration that yields only 2 ATPs for every glucose molecule.
• Lactic acid fermentation’s equation appears as follows:
• C6H12O6 → C3H6O3 + energy
• Because lactic acid ferments in the muscles, lactic acid builds up in the tissues and causes muscle soreness.
• Anaerobic respiration makes you feel weak and short of breath because it makes less energy per glucose molecule than aerobic respiration.

Alcoholic fermentation by yeasts

• Another anaerobic respiration process that uses anaerobic organisms like yeast is fermentation.
• Yeasts go through anaerobic respiration when they are combined with carbohydrate-rich substances that have a low oxygen concentration in the container.
• The yeast then ferments the carbs, converting them into ethyl alcohol.
• However, since the alcohol created in the bottle is harmful to yeast, they begin to die as the alcohol concentration rises.
• Only about 30% of alcohol can be made with yeast. Distillation is used to make more alcohol.
• Similar to the fermentation of lactic acid, fermentation only produces 2 ATPs as energy.
• Fermentation’s total response may be expressed as:
• C6H12O6 → C2H5OH + CO2 + energy

Fermentation in methanogens

• Prokaryotes called methanogens belong in the archaea.
• These organisms are known as methanogens because, when they oxidise carbohydrates in the absence of oxygen, they create methane as a by-product. Methanogenesis is the name of this process.
• This particular method of fermentation also produces methanol, a separate sort of alcohol. Methanol poisoning is another name for this phenomenon.
• Methanogens (such as Methanosarcina barkeri) oxidise plant cellulose to make methanol rather than ethyl alcohol, as yeasts do.
• Some people who consume too much methanol may experience death or nerve damage.
• The result of methanol production as a whole is:
• C6H12O6 → CH3OH + CO2 + energy

Proton acid fermentation in cheese

• Fermentation of propionic acid happens when certain microorganisms, including
• Lactose and glucose are used by Propionibacterium shermanii to make propionic acid and carbon dioxide
• Swiss cheese is the product where this method is used the most often.
• The carbon dioxide gas that is made during this process causes bubbles to form in the cheese. The carboxylic acid also gives the cheese its unique taste.
• Like all other anaerobic respiration processes, this one takes place when there is little or no oxygen present.
• This process’s overall response is:

C12H22O11    →    C3H6O2 + CO2 + energy

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