Respiration

• Adenosine triphosphate (ATP) is a nucleotide derivative consisting of ribose, adenine, and three phosphate groups
• Energy is released when ATP is hydrolysed to form ADP and a phosphate molecule, a process catalysed by ATP hydrolase
• The inorganic phosphate released from ATP hydrolysis can phosphorylate other compounds, making them more reactive
• Condensation of ADP and inorganic phosphate catalysed by ATP synthase produces ATP during photosynthesis and respiration
• ATP is synthesized by:

  • Chemiosmosis: movement of protons across a membrane synthesizing ATP
  • Substrate-level phosphorylation: ATP made from ADP and a phosphate group transferred from a highly reactive intermediate, e.g., during glycolysis and the Krebs cycle
• Respiration is the breakdown of a respiratory substrate like glucose to produce energy in the form of ATP, with two types: aerobic (with oxygen) and anaerobic (without oxygen)
• Some organisms and tissues can respire in both aerobic and anaerobic conditions, producing different end-products like ethanol, carbon dioxide, and lactate
• Glycolysis is the first process of both aerobic and anaerobic respiration, where glucose is phosphorylated to produce 1,6 bisphosphate, leading to the production of pyruvate, ATP, and NADH
• In anaerobic respiration, pyruvate is converted into lactate with the help of NADH, which is then converted back to pyruvate in the liver
• The link reaction is the next step in aerobic respiration after glycolysis, where pyruvate undergoes oxidative decarboxylation to form acetyl coenzyme A (CoA)
• The Krebs Cycle occurs in the mitochondrial matrix, where acetyl CoA delivers the acetyl group to form citrate, leading to the production of carbon dioxide, ATP, reduced NAD, and reduced FAD
• Oxidative phosphorylation is the process where ATP is synthesized in the electron transport chain in mitochondria, generating the majority of ATP in aerobic respiration
• Respiratory substrates like carbohydrates, lipids, and proteins release varying amounts of energy, with different respiratory quotient (RQ) values for each substrate
• Rice adaptations for aerobic respiration include submerged roots, aerenchyma in stems and roots for gaseous exchange, and fast stem growth when submerged under excessive water
• Anaerobic respiration includes lactate fermentation in mammals and alcohol fermentation in yeast, with different end-products and processes
• Aerobic respiration yields much more ATP than anaerobic respiration due to the complete breakdown of glucose