Cellular Respiration and Fermentation Processes

• Fermentation and cellular respiration are metabolic processes that break down glucose to produce energy in the form of ATP.

Key Differences

• In fermentation, NADH does not undergo oxidative phosphorylation to synthesize ATP.
• In respiration, NADH is utilized in oxidative phosphorylation, synthesizing 3 ATPs per NADH.
• Fermentation is the chemical breakdown of glucose by microorganisms, releasing heat and effervescence.
• Respiration involves chemical reactions that oxidize food to produce energy, releasing water and carbon dioxide.
• Fermentation doesn't require oxygen, while respiration mandates it.
• Water is a byproduct of respiration, but not fermentation.
• Fermentation occurs in the cytoplasm, while respiration occurs in both the cytoplasm and mitochondria.
• Fermentation synthesizes only 2 ATPs, whereas respiration synthesizes 36 ATPs.
• The substrate is not entirely broken down in fermentation, but it is entirely broken down in respiration.
• Ethanol and lactic acid fermentations are fermentation types, while aerobic and anaerobic respiration are respiration types.
• The final electron acceptor is an organic molecule in fermentation, and oxygen in respiration.
• Regeneration of NAD+ in fermentation does not involve ATP production, while it synthesizes three ATPs in respiration.
• Fermentation usually occurs in microorganisms; respiration is found in higher organisms.

Similarities

• Both cellular respiration and fermentation start with the breakdown of glucose into pyruvate.
• Hexoses are substrates in both processes.
• Pyruvate is an intermediate compound in both processes.
• Inorganic phosphate increases the rate of sugar breakdown in both processes.

Cellular Respiration

• Respiration is a group of chemical reactions associated with energy production through complete food oxidation.
• Animals use mitochondrion during respiration
• It releases water and carbon dioxide.
• It produces 36 ATPs and occurs in the mitochondria and cytoplasm.
• It occurs in three steps: glycolysis, the citric acid cycle, and the electron transport chain.
• Glycolysis occurs in the cytoplasm, where two pyruvate molecules are synthesized.
• Pyruvate molecules are transported to the mitochondrial matrix.
• Each molecule releases a carbon dioxide molecule and transforms into acetyl CoA through oxidative decarboxylation.
• Acetyl-CoA enters the citric acid cycle, oxidizing a glucose molecule into 6 carbon dioxide molecules, creating 2 GTPs, 6 NADH, and 2FADH2.
• Oxidative phosphorylation creates ATP when NADH and FADH2 combine with oxygen in the inner mitochondrial membrane.
• Electrons are transported through a group of electron carriers from NADH and FADH2 in the electron transport chain.
• The cellular respiration equation is C6H12O6 +6O2 —› 6CO2 + 6H2O +ATP.
• Aerobic respiration occurs in the presence of oxygen.
• Anaerobic respiration occurs in the absence or limited availability of oxygen.
• Photoautotrophs depend on cellular respiration when photosynthesis cannot be conducted.
• Chemoautotrophs transform inorganic molecules into energy under extreme conditions, like the absence of sunlight and oxygen.
• Heterotrophs eat autotrophs and convert stored biomass into energy through cellular respiration.

Fermentation

• Fermentation involves the chemical processing of organic substrates like glucose by microorganisms, releasing heat and effervescence.
• It occurs in the cytoplasmic region of cells, yielding a net result of 2 ATPs.
• It comprises two steps: glycolysis and partial oxidization of pyruvate.
• After glycolysis, pyruvate acts as the electron acceptor in lactic acid fermentation, and acetaldehyde in ethanol fermentation.
• Ethanol fermentation occurs in yeast without oxygen.
• Lactic acid fermentation takes place in bacteria; in animals, it occurs in muscles without oxygen.
• Glycolysis is the same for both processes, breaking down pyruvate into two pyruvate molecules and synthesizing 2 ATPs.
• During glycolysis, 2 molecules of NADH are formed by taking electrons from glyceraldehyde-3-phosphate.
• In ethanol fermentation, pyruvate is decarboxylated to acetaldehyde, releasing carbon dioxide, and acetaldehyde converts into ethanol.
• In lactic acid fermentation, pyruvate is converted into lactic acid, then oxidized back to lactate.

Types of Fermentation

• C6H12O6 —› 2C2H5OH + 2CO2 + 2ATP is the chemical equation for ethanol fermentation.
• C6H12O6 —› 2C3H6O3 + 2ATP is the chemical equation for lactic acid fermentation.

Examples of Fermentation

• The human body uses fermentation for energy when oxygen is insufficient, such as during strenuous exercise.
• Lactic acid fermentation occurs in muscle cells to produce energy when oxygen supply is limited.
• Fermentation is an alternative pathway for ATP production, especially in obligate anaerobes.
• Neocallimastix fungi digest cellulose through fermentation in herbivorous animals.
• Bacteroides bacteria degrade sugar derivatives from plants in the human colon through fermentation.
• Facultative anaerobes like Saccharomyces cerevisiae and Saccharomyces pombe ferment even in the presence of oxygen.
• Kluyveromyces lactis yeast carries out more respiration than fermentation if oxygen is present.
• Lactic acid fermentation by fungi and bacteria is used to synthesize yogurt and cheese.
• Alcohol fermentation by yeast is used to synthesize liquor and wine.

Explore the key differences between cellular respiration and fermentation, focusing on the roles of NADH and oxygen. Understand the significance of ATP production and identify the shared intermediate compound in both processes. Ideal for biology students to study metabolic pathways.