cellular respiration

• Cellular respiration


  Breaks down glucose to release ATP energy required for cell metabolism

  
• Cellular respiration


  • Occurs in cytoplasm and mitochondria
  • Uses glucose and oxygen and produces ATP, carbon dioxide, and water
  • Transfers chemical energy stored in glucose to chemical energy of ATP

  
• Types of cellular respiration


  • Aerobic
  • Anaerobic
• Aerobic cellular respiration


  • Requires oxygen
  • Present in animal and plants

  
• Anaerobic cellular respiration


  • Does not require oxygen
  • Present in bacterial and Archean species

  
• Stages in aerobic cellular respiration


  1. Glycolysis

  2. Link reaction

  3. Krebs cycle

  4. Electron transport chain

  
• Glycolysis


  Splits 6 carbon (6C) glucose molecules into two 3 carbon (3C) molecules

  
• Link reaction


  Pyruvate is converted into acetyl through coenzyme A

  
• Krebs cycle


  Makes a supply of energy-rich loaded coenzymes

  
• Electron transport chain


  Transfers energy from electrons supplied by loaded coenzymes to make ATP
• In total: 30-32 ATP yield
• Glycolysis


  Sugar splitting, first step of cellular respiration, converts glucose 6C into pyruvate 3C, occurs in cytosol, produces Pyruvate and ATP

  
• Link reaction


  Pyruvate oxidation occurs to allow the molecule to enter Krebs cycle, Pyruvate molecules are converted to acetyl CoA through coenzyme A, Acetyl CoA is produced and 1 carbon is released as carbon dioxide

  
• Krebs cycle


  Acetyl CoA splits into 2-carbon acetyl groups, 2-carbon acetyl groups combine with a 4C molecule (pyruvate), Produces CO2 + ATP, Loaded coenzymes

  
• Electron transport chain


  Can only operate if a supply of oxygen is available, Series of hydrogen and electron carriers, located on the membranes of the mitochondrial cristae, Electrons from glycolysis and the Krebs cycle are transported to the electron transport chain as NADH and FADH2
• Anaerobic cellular respiration is fast rate of production, enabling more ATP, Occurs in cytosol

  
• Anaerobic pathways


  • All organisms can metabolize glucose anaerobically via glycolysis
  • Fermentation pathways for glucose metabolism operate without oxygen
  • Despite low energy yield, fermentation is faster, allowing for increased ATP production
  • Alternative electron acceptors like ethanal or pyruvate are necessary in anaerobic conditions, as in alcoholic or lactic acid fermentation

  
• Lactic acid fermentation


  Anerobic respiration, 2 ATP yield, Without oxygen, glycolysis (Glucose to pyruvate) converts pyruvate to lactic acid, Lactic acid is either metabolized in muscles or sent to the liver for replenishing carbohydrate stores, Lactic acid is toxic to the body and must be removed as soon as possible

  
• Yeast fermentation - alcoholic


  Glycolysis -> pyruvate converts to ethanol + CO2, Baker's yeast and brewer's yeast undergo alcohol fermentation, producing ethanol and carbon dioxide, They differ in the ratio of ethanol to carbon dioxide produced, making them unsuitable substitutes in baking or brewing, Pyruvate becomes ethanal (acetaldehyde) and C02 + no link reaction, ethanal becomes ethanol, products are C02 waste product and ethanol
• 2 ATP yield -> produced in glycolysis

  
• Factors affecting rate of cellular respiration


  • Temperature
  • Glucose availability
  • Oxygen concentration

  
• As temperature increases


  Respiration rate increases
• After optimal temperature, enzymes denature and no longer function -> decreasing rate of enzyme activity
• As glucose levels increase


  Respiration rate increases
• As oxygen levels increase


  Respiration rate increases
• Cell may undergo anaerobic respiration when oxygen concentration is low, These are fermentation reactions to keep the cell alive-> lower efficiency + lower rate of respiration

  
• gylcolysis inputs = Glucose, ADP + Pi , NAD+
• Glycolysis outputs = Pyruvate, ATP, NADH
• krebs cycle inputs =  Pyruvate , ADP + Pi , NAD+, FAD
• krebs cycle output: CO2 , ATP , NADH , FADH2
• electron transport chain input: O2 , ADP + Pi , NADH , FADH2
• electron transport outputs: H2O , ATP , NAD+, FAD
• temperature affects cellular respiration in yeast by influencing enzyme activity and metabolic rate
• Lower pH levels can lead to decreased enzyme activity, resulting in slower rates of hydrogen peroxide breakdown and oxygen production.
• facts affecting cellular respiration = temperature, glucose availability, oxygen concentration
• Lactic acid - Animals Pyruvate --> lactic acid 

  Alcoholic - Yeast --> Ethanal