Respiration

• What is the structure of ATP?

  Adenine base + ribose sugar + three phosphate groups
• What type of reaction breaks down ATP?

  Hydrolysis: ATP + H₂O → ADP + Pi + energy
• Why is ATP useful as an energy source in cells?

  Small, soluble, releases energy in manageable amounts
• What is phosphorylation?

  Adding a phosphate group to a molecule
• What are the two main ways ATP is formed in respiration?

  Substrate-level phosphorylation & oxidative phosphorylation
• What is substrate-level phosphorylation?

  Direct transfer of a phosphate from a substrate to ADP
• What is oxidative phosphorylation?

  Production of ATP using energy from electrons
• What are hydrogen carriers?

  Coenzymes like NAD and FAD that carry hydrogen
• What happens when hydrogen carriers are reduced?

  They gain hydrogen, storing energy for transfer
• Where does the electron transport chain occur?

  Inner mitochondrial membrane (cristae)
• How does the ETC make ATP?

  Electrons release energy, protons pumped into space
• What is chemiosmosis?

  Movement of protons down their gradient through ATP synthase
• What is the final electron acceptor in aerobic respiration?

  Oxygen, forming water with electrons and protons
• Why are hydrogen carriers essential in respiration?

  They transfer energy from glucose breakdown to the ETC
• What is glycolysis?

  First stage of aerobic respiration
• What happens to glucose during glycolysis?

  It is broken down into two pyruvate molecules
• Where in the cell does glycolysis take place?

  In the cytoplasm of the cell
• What is the net ATP gain from glycolysis?

  Net gain of 2 ATP molecules
• What coenzyme is reduced during glycolysis?

  NAD is reduced to NADH
• What is the first step of glycolysis?

  Phosphorylation of glucose to glucose-6-phosphate
• What is the purpose of phosphorylation in glycolysis?

  To make glucose more reactive and trap it
• What is meant by “substrate-level phosphorylation” in glycolysis?

  Direct transfer of phosphate to ADP to form ATP
• How many pyruvate molecules are produced per glucose in glycolysis?

  Two pyruvate molecules are produced
• What is the total ATP produced in glycolysis before subtracting the ones used?

  Four ATP molecules are produced
• Why is glycolysis important if oxygen is not present?

  It allows ATP production anaerobically
• What are the key steps and outcomes of glycolysis?

  • Glycolysis breaks down glucose into pyruvate
  • Takes place in the cytoplasm
  • Produces a net gain of 2 ATP
  • Reduces NAD to NADH
  • Involves phosphorylation of glucose
  • Allows anaerobic ATP production
• Where does the Link Reaction take place?

  Mitochondrial matrix
• What molecule enters the Link Reaction?

  Pyruvate (3C)
• What happens to the 2C molecule left behind after decarboxylation?

  It is oxidised, reducing NAD → NADH
• What is removed from pyruvate during the Link Reaction?

  CO₂ (decarboxylation)
• What does the 2C acetyl group combine with?

  Coenzyme A, forming Acetyl CoA
• What are the products per pyruvate in the Link Reaction?

  1 Acetyl CoA, 1 NADH, 1 CO₂
• What are the products per glucose in the Link Reaction?

  2 Acetyl CoA, 2 NADH, 2 CO₂
• Is ATP produced in the Link Reaction?

  No
• Where does the Krebs cycle take place?

  Mitochondrial matrix
• What molecule enters the Krebs cycle?

  Acetyl CoA (2C)
• What does acetyl CoA combine with at the start of the Krebs cycle?

  Oxaloacetate (4C) → forms citrate (6C)
• How many turns of the Krebs cycle occur per glucose molecule?

  2 turns (1 per acetyl CoA)
• How many CO₂ are released per acetyl CoA?

  2 CO₂
• How many NADH are made per acetyl CoA?

  3 NADH