Respiration

• What is aerobic respiration?


  Requires oxygen and produces carbon dioxide, water, and ATP
• What is anaerobic respiration?


  Takes place without oxygen and produces lactic acid in animals or ethanol and carbon dioxide in plants
• What is the first stage of respiration?

  Glycolysis
• Where does glycolysis take place?


  Cytoplasm of the cell
• What is the first step of glycolysis?


  Phosphorylation of glucose to glucose phosphate by the hydrolysis of 2 ATP molecules
• What is the second stage of glycolysis?


  Glucose phosphate is split into two molecules of triose phosphate
• What is the third stage of glycolysis?

  Triose phosphate is oxidised by NAD to form reduced NAD
• What is the last stage of glycolysis?


  Triose phosphate is converted to pyruvate, and two molecules of ATP are regenerated from ADP
• What are the products of glycolysis and where do they go next?


  2 x pyruvate goes to the link reaction, 2 x ATP is a useful product, and 2 x reduced NAD goes to oxidative phosphorylation
• Why does glycolysis take place in the cytoplasm and why is it anaerobic?


  It occurs in the cytoplasm because enzymes required are found there, and it is anaerobic as it does not require oxygen
• What is the next step of aerobic respiration after glycolysis?

  Link reaction
• Where does the link reaction take place?


  Matrix of mitochondria
• What happens to the pyruvate during the link reaction?


  Pyruvate is oxidised to acetate, losing a carbon to carbon dioxide, and two hydrogens are accepted by NAD to form reduced NAD
• What is the last step of the link reaction?


  Acetate combines with coenzyme A to produce acetylcoenzyme A, which goes to the Krebs cycle
• What is the next step of aerobic respiration after the link reaction?

  Krebs cycle
• What happens to the acetylcoenzyme A in the Krebs cycle?


  It reacts with a 4 carbon molecule (oxaloacetate) to produce a 6 carbon molecule (citrate), and coenzyme A is produced and goes back to the link reaction
• What happens to the 6 carbon molecule in the Krebs cycle?


  It loses 2x carbon dioxide to give a 4 carbon molecule, FAD is reduced to reduced FAD, and a single ATP is produced as a result of substrate level phosphorylation
• What are the two ways of making ATP?

  Substrate level phosphorylation and oxidative phosphorylation
• Where do protons come from in oxidative phosphorylation?


  From the oxidation of reduced NAD and reduced FAD, where hydrogen ions are released and NAD and FAD are formed
• How is energy released for chemiosmosis?


  Electrons pass along an electron transfer chain through a series of redox reactions, releasing energy
• What happens during chemiosmosis?


  Protons are pumped from the matrix into the inner membrane space across the inner membrane, building up an electrochemical gradient, and protons move back into the matrix via ATP synthase
• What happens at the end of the electron transport chain?


  Electrons combine with protons and oxygen to form water, with oxygen being the final electron acceptor
• What is the first stage of anaerobic respiration?

  Glycolysis
• What is the equation for anaerobic respiration in plants?


  Pyruvate + reduced NAD → ethanol + carbon dioxide + oxidised NAD
• What is the equation for anaerobic respiration in animals?


  Pyruvate + reduced NAD → lactate + oxidised NAD