Biology: Fermentation and Cellular Respiration

Fermentation and Cellular Respiration

• Fermentation and cellular respiration are biological processes that allow organisms to utilize energy stored in biological molecules.
• The conversion of ATP to ADP releases energy.
• These processes are characteristic of all life forms.
• Fermentation and cellular respiration release chemical energy from organic molecules like glucose.
• Oxygen is not used in fermentation; however, it is used in cellular respiration.
• Fermentation and anaerobic respiration are not the same process.

Cellular Respiration in Eukaryotes

• Cellular respiration in eukaryotes involves a coordinated enzyme-catalyzed sequence of reactions that extract energy from biological macromolecules.
• The process involves the breakdown of glucose to create ATP.
• Cellular respiration occurs in multiple metabolic pathways.
• Glycolysis occurs in the cytoplasm.
• Pyruvate oxidation occurs in mitochondria.
• Krebs Cycle occurs in mitochondria.
• Electron transport chain occurs in mitochondria.

Electron Transport Chain

• The electron transport chain (ETC) facilitates a series of coupled reactions used during cellular respiration.
• Electron transport chains occur in cell membranes of chloroplasts, mitochondria, and prokaryotes.
• Electron transport chains allow for a controlled and efficient transfer of energy.
• Electron carriers (NADH and FADH2) deliver electrons to the ETC.
• ATP synthase uses the electrochemical/proton gradient to synthesize ATP.

Structure of Mitochondria and Cellular Respiration

• The chemical reaction in cellular respiration is: C₆H₁₂O₆ + 6O₂ →6CO₂ + 6H₂O + ATP. (glucose + oxygen →carbon dioxide + water + energy)
• The process occurs in the mitochondria of eukaryotic cells.

Cellular Respiration in Detail

• Cellular respiration involves glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation.
• The different phases of the process take place in different parts of the cell.
  • Glycolysis takes place in the cytoplasm.
  • Pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation take place in mitochondria.

Glycolysis

• Glycolysis is a biochemical pathway that releases energy stored in glucose.
• Glycolysis results in the production of pyruvate, NADH, and ATP.
• The net gain of ATP from glycolysis is 2.
• If oxygen is not present, pyruvate undergoes fermentation to lactic acid or ethanol.
• If oxygen is present, pyruvate is transported into the mitochondrion for further processing.
• Pyruvate is oxidized, and a product of this oxidation enters the Krebs cycle.

Krebs Cycle

• The Krebs Cycle (Citric Acid Cycle) releases carbon dioxide from organic intermediates.
• The Krebs cycle produces energy-carrying molecules.
• The cycle involves many key reactions where carbon dioxide is released.
• Energy electrons are transferred to NADH and FADH2, then to the electron transport chain.
• ADP is phosphorylated to form ATP.

Krebs Cycle (Continued)

• The main function of the Krebs cycle is to transfer high-energy electrons to molecules that carry them to the electron transport chain.
• It is also sometimes called the citric acid cycle as citric acid is the first molecule formed.

Electron Transport Chain Reactions

• The electron transport chain takes place across the inner membrane of the mitochondrion.
• Proteins in the chain use energy from electrons to pump hydrogen ions against a concentration gradient.
• The hydrogen ions are pumped into the space between the inner and outer membranes of the mitochondria.
• The hydrogen ions build up in the inner membrane.
• ATP is produced via diffusion of hydrogen ions through ATP synthase.
• For each pair of electrons that moves through the ETC, 3 ATP molecules are formed.
• Oxygen acts as the final electron acceptor and combines with hydrogen ions to form water.

Oxidative Phosphorylation

• Oxidative phosphorylation is the process where ATP is formed from the transfer of electrons from NADH or FADH₂ to O₂.
• This process takes place in mitochondria.

Lactic Acid Fermentation

• Lactic acid fermentation is an anaerobic process that regenerates NAD⁺.
• This process converts pyruvate into lactate or lactic acid.
• This occurs when oxygen is not readily available in cells, like during intense exercise.
  • In muscles, lactic acid buildup can result in fatigue.

Ethanol Fermentation

• Ethanol fermentation is also an anaerobic process that regenerates NAD⁺.
• In this process, pyruvate is converted into ethanol and carbon dioxide.

Explore the essential biological processes of fermentation and cellular respiration. This quiz covers how organisms extract energy from glucose and the distinct mechanisms of these processes. Understanding the differences between eukaryotic and anaerobic respiration is crucial for insights into cellular energy production.