Cellular respiration

• Acetyl group


  Produced by breakdown of pyruvate; joins with oxaloacetate in the citric acid cycle
• ADP


  Adenosine diphosphate; molecule that is phosphorylated to produce ATP
• ATP


  Adenosine triphosphate; molecule used for energy transfer in cells
• ATP synthase


  Membrane-bound enzyme that synthesises ATP
• Cellular respiration


  Release of energy from respiratory substrates
• Citrate


  First substance produced in the citric acid cycle
• Citric acid cycle


  Second stage of aerobic respiration occurring in the matrix of mitochondria
• Coenzyme A


  Substance that carries acetyl groups into the citric acid cycle
• Dehydrogenase


  Enzymes that remove hydrogen from their substrates
• Electron transport chain


  Group of proteins embedded in membranes of mitochondria
• Glucose


  Sugar which is the main respiratory substrate in cells
• Glycolysis


  First stage in cellular respiration
• Intermediate


  Substance in a metabolic pathway between the original substrate and the end product
• Matrix


  Central cavity of a mitochondrion where citric acid cycle occurs
• Mitochondrion


  Cell organelle in which glycolysis and the citric acid cycle occur
• NAD


  Hydrogen carrier important in the citric acid cycle
• Oxaloacetate


  Substance that combines with the acetyl group in the citric acid cycle to form citrate
• Phosphate (Pi)


  Inorganic phosphate used to phosphorylate ADP
• Phosphorylation


  Addition of phosphate to a substance
• Pyruvate


  The end product of glycolysis
• A molecule of ATP (Adenosine Triphosphate) is composed of an adenosine molecule (A) joined by high energy bonds to three inorganic phosphates (PI)
• Breakdown of ATP


  Adenosine ATP ADP + P
• Regeneration of ATP


  ADP + P ATP
• Most cells will use GLUCOSE as their main respiratory substrate
• Glucose is broken down in a series of enzyme controlled reactions to release the energy needed to produce ATP
• Mitochondria


  • Double unit membrane; outer membrane is smooth, inner membrane is greatly folded into cristae
• Matrix


  Fluid-filled area that contains enzymes required for aerobic respiration
• Cristae


  Folds that provide a large surface area for aerobic respiration (Electron Transport System)
• Stages of Respiration


  1. Glycolysis (in cytoplasm)

  2. Citric Acid Cycle (in matrix of mitochondrion)

  3. Electron Transport Chain (on folded inner membrane of mitochondrion)
• Glycolysis


  Breakdown of glucose to pyruvate in the cytoplasm, does not require oxygen
• Glycolysis


  2 ATP needed for phosphorylation of glucose and intermediates (Energy Investment Phase), but 4 ATP produced (Energy Pay-Off Phase), net gain of 2 ATP
• Dehydrogenase enzymes


  Remove hydrogen ions and electrons and pass them to NAD, forming NADH
• Citric Acid Cycle


  Acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate, gradually converted back to oxaloacetate, generates ATP and releases CO2
• For every glucose molecule there are two molecules of pyruvate produced, so the citric acid cycle will turn twice
• Electron Transport Chain


  NADH carries high energy electrons and hydrogen to the inner mitochondrial membrane, electrons passed along the chain releasing energy to pump hydrogen ions across the membrane, flow of hydrogen ions back through ATP synthase results in ATP synthesis, hydrogen ions and electrons combine with oxygen to form water
• ATP synthase


  Membrane protein that controls the flow of hydrogen ions from high to low concentration, catalyses the synthesis of ATP from ADP+P
• ATP is used to transfer energy to cellular processes which require energy