1.7

• Cellular respiration

  The process by which glucose is broken down in a series of enzyme controlled stages to release energy for cells to use
• Aerobic respiration equation

  Glucose + oxygen → energy (ATP) + carbon dioxide +water
• ATP

  Adenosine Triphosphate, made up of Adenosine and 3 Phosphate molecules. The bond between the final 2 phosphates is a high energy bond, when broken energy is released.
• Energy transfer via ATP

  ATP is used to transfer energy to synthetic pathways and other cellular processes where energy is required, e.g. protein synthesis, DNA replication.
• Role of ATP in energy transfer

  • ATP is used to transfer energy to cellular processes which require energy e.g. protein synthesis
• Stages in cellular respiration

  1. Glycolysis

  2. Citric Acid cycle

  3. Electron transport chain
• Glycolysis

  1. Breakdown of glucose to pyruvate in the cytoplasm

  2. Energy Investment Phase

  3. Energy Pay off Phase
• Energy Investment Phase

  ATP is required for the phosphorylation of glucose and intermediates, where phosphate from ATP is added breaking it down to ADP
• Energy Pay Off Phase

  Generation of more ATP, dehydrogenase enzymes remove hydrogen ions and electrons from intermediates and pass them to NAD forming NADH
• Phosphorylation

  Enzyme controlled process by which a phosphate group is added to a molecule
• Glycolysis occurs in the cytoplasm of cells and does not require oxygen, so it can occur under both aerobic and anaerobic (fermentation) conditions
• In aerobic conditions

  Pyruvate (from glycolysis) is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A
• Mitochondria

  • The site of aerobic respiration, composed of a double membrane
• Citric Acid Cycle

  1. Acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate

  2. Citrate is gradually converted back into oxaloacetate

  3. Generates ATP, releases carbon dioxide, forms NADH as dehydrogenase enzymes remove hydrogen ions and electrons and pass them to NAD
• Dehydrogenase enzymes

  Remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH. This occurs in both glycolysis and the citric acid cycle.
• Electron Transport Chain (ATP synthesis)

  1. Series of carrier proteins attached to the inner mitochondrial membrane

  2. Electrons are passed along the chain, releasing energy

  3. This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane

  4. The flow of these hydrogen ions back through the membrane protein ATP synthase results in the production of ATP

  5. Hydrogen ions and electrons combine with oxygen to form water
• The electron transport chain and ATP synthesis take place in the inner mitochondrial membrane