Respiration

• What is respiration?


  A complex multi-step reaction pathway, in which glucose and oxygen are the inputs, and carbon dioxide and water are the outputs.
• What are the stages of respiration?

  Glycolysis, link reaction, krebs cycle, and oxidative phosphorylation.
• Where do each of these processes occur?

  Glycolysis - Cell cytoplasm.

  Link reaction - Mitochondrial matrix.

  Krebs cycle - Mitochondrial matrix.

  Oxidative Phosphorylation - Inner mitochondrial membrane.
• Which of these processes occur in aerobic respiration?

  Glycolysis, link reaction, krebs cycle, and oxidative phosphorylation.
• Which of these processes occur in anaerobic respiration?

  Glycolysis.
• What is the role of the mitochondria?

  ATP synthesis, producing the chemical energy required to power the cells biochemical reactions.
• Why is the mitochondria double membraned?

  This allows increased selectivity in substance exchange.
• What are the structures of the mitochondria?


  Outer and inner mitochondrial membrane, intermembrane space, cristae, mitochondrial matrix, ribosomes, mitochondrial DNA.
• What is the outer and inner mitochondrial membrane?


  OUTER - Permeable to small molecules, a phospholipid bilayer, separating the contents of the mitochondrion from the rest of the cell.

  INNER - Less permeable, a phospholipid bilayer, containing the electron transport chain and ATP synthase.
• What is the intermembrane space?

  The space between the two membranes, where proteins are pumped by the electron transport chain, with the space being small, causing the concentration to build quickly; it has a low pH due to a high concentration of protons or hydrogen ions.
• What is the cristae?

  This describes the highly folded nature of the inner mitochondrial membrane, which increases surface area, meaning there are more electron transport chain carriers, and ATP synthase enzymes, so more ATP can be produced during oxidative phosphorylation.
• What is the mitochondrial matrix?

  This is the inner space, which contains enzymes for the krebs cycle and the link reaction, and it also contains mitochondrial DNA.
• What are the ribosomes?

  Cellular organelles responsible for protein synthesis, 55S.
• What is the mitochondria DNA?

  Circular chromosomes found in the matrix.
• Where will more mitochondria be found in the organism?

  Active muscle cells, as increased cellular activity means they require more ATP.
• What is the equation for aerobic respiration?

  C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP

  glucose + oxygen = carbon dioxide + water + energy
• What is the equation for anaerobic respiration?

  Glucose -> Lactic Acid (in animals) or Ethanol + Carbon Dioxide (in yeast).
• What is glycolysis?


  Metabolic pathway that converts glucose into pyruvate, producing ATP and NADH in the process.
• What are the steps of glycolysis?

  1. Phosphorylation - two molecules of ATP are required, which release two phosphates that attach to a six carbon glucose molecule, forming HEXOSE BISPHOSPHATE.
  2. Lysis - This destabilises the molecule, causing it to split into two molecules of three carbon TRIOSE PHOSPHATE.
  3. Phosphorylation - Another phosphate group is added to each triose phosphate, forming two molecules three carbon of TRIOSE BISPHOSPHATE.
  4. Dehydrogenation - The two triose bisphosphate molecules are oxidised by the removal of hydrogen atoms to form two molecules of three carbon PYRUVATE.
• What is the final stage of glycolysis?

  NAD coenzymes accept the removed hydrogens, causing them to be reduced into two reduced NAD (NADH) molecules, and ADP accept the phosphates from the triose bisphosphate molecules to form four ATP molecules.
• Where do the phosphate groups come from in the second phosphorylation stage?

  They come from the free inorganic phosphate (Pi) ions present in the cytoplasm.
• What are the outputs of glycolysis?

  Four ATP, two reduced NAD, and two pyruvate.
• What are the net outputs of glycolysis?

  Two ATP, two reduced NAD, and two pyruvate.
• What is substrate level phosphorylation?

  The formation of ATP without the use of an electron transport chain, with it being formed by the transfer of a phosphate group from a phosphorylated intermediate to ADP.
• What is the link reaction?

  This is also known as oxidative decarboxylation, and links anaerobic glycolysis in the cytoplasm, with the aerobic steps of respiration in the mitochondria.
• How does pyruvate enter the mitochondrial matrix?

  Pyruvate leaves the cytoplasm and enters the mitochondrial matrix by active transport via specific carrier proteins.
• What are the steps of the link reaction?

  1. Pyruvate undergoes oxidative decarboxylation, in which carbon dioxide is removed, along with hydrogen, producing a two carbon molecule of ACETATE (an acetyl group).
  2. The removed hydrogen atoms are accepted by NAD to form NADH (reduced NAD).
  3. The acetate combines with coenzyme A (CoA), forming acetyl coenzyme A (acetyl CoA).
• What are the outputs of the link reaction?

  Acetyl CoA, NADH, and CO2.
• What does the acetyl CoA do?

  The acetyl CoA delivers the acetyl group to the next stage of aerobic respiration, the krebs cycle.
• What does the NADH do?

  The NADH is carried through to be used in oxidative phosphorylation to synthesise ATP.
• What happens to the CO2?

  The CO2 either diffuses away and be removed from the organism as metabolic waste, or in autotrophic organisms (those who produce their own nutrients) may be used as a raw material in photosynthesis.
• What is the krebs cycle?

  This is a process that also occurs in the mitochondrial matrix and results in the breakdown of an acetyl group, with this acetyl group being what remains of the glucose that entreated glycolysis.
• What are the steps of the Krebs cycle?

  1. Acetyl CoA delivers the acetyl group to the Krebs cycle, and the two carbon acetyl group combines with the four carbon oxaloacetate, forming a six carbon CITRATE.
  2. The citrate undergoes decarboxylation and dehydrogenation to releasing carbon dioxide and hydrogen, and producing a five carbon intermediate.
  3. The intermediate undergoes decarboxylation and dehydrogenation reactions, eventually regenerating four carbon oxaloacetate.
• What is the net produce of the Krebs cycle?

  Three reduced NAD (NADH), two CO2, one reduced FAD (FADH), and one ATP.
• How is reduced NAD and FAD produced?

  The hydrogen atoms released during dehydrogenation are picked up by the coenzymes NAD and FAD, reducing them, and go on to be used in the final stage of aerobic respiration.
• How is ATP produced in the Krebs cycle?

  Substrate-level phosphorylation.
• Why are coenzymes such as NAD and FAD important in respiration?

  They act as carriers for protons, electrons, and functional groups between the enzyme catalysed reactions of respiration, such as the transfer of protons and electrons between redox reactions, which have a major role in respiration.
• How are NAD and FAD coenzymes?

  They accept protons and elections released during glucose breakdown in respiration.
• What is the difference between NAD and FAD?

  • NAD is in all stages of cellular respiration, but FAD is only in the Krebs cycle stage.
  • NAD accepts one hydrogen, FAD accepts two.
  • Reduced NAD is oxidised at the beginning of the electron transport chain, releasing protons and electrons, reduced FAD is oxidised further along the chain.
  • Reduced NAD results in the synthesis of three ATP molecules but reduced FAD results in the synthesis of two.
• What is a coenzyme?

  A non-protein organic molecule that assists enzymes in carrying out their functions, but isn’t used in reactions themselves.