Module 5.2.2- Respiration

• What is the need for cellular respiration?


  Active transport e.g. uptake of nitrates by root hair cells, loading sucrose, conduction of nerve impulses, reabsorption etc.

  Anabolic reactions

  Movement
• MITOCHONDRIA structure- Outer membrane


  Separates contents of mitochondria from the rest of the cell
• MITOCHONDRIA structure- Inner membrane


  Contains electron transport chains and ATP synthase
• MITOCHONDRIA structure- Intermembrane space


  Protons are pumped into this space by the ETC. Site of oxidative phosphorylation.
• MITOCHONDRIA structure- Matrix


  Contains enzymes for link reaction and Krebs cycle. Also contains mitochondrial DNA.
• MITOCHONDRIA structure- Cristae


  Folds on the inner membrane that hold the electron carriers of aerobic respiration. Increase surface area available for oxidative phosphorylation.
• Where does Glycolysis occur?


  In the cytoplasm (cytosol)
• Glycolysis- STAGE 1. What is formed?


  PHOSPHORYLATION- Glucose is phosphorylated using 2 ATP molecules forming HEXOSE BISPHOSPHATE
• Glycolysis- STAGE 2. What is formed?


  LYSIS- The molecule is destabilized causing it to split into 2 TRIOSE PHOSPHATE molecules
• Glycolysis- STAGE 3. What is formed?


  PHOSPHORYLATION- Triose phosphate molecules are phosphorylated with inorganic phosphate ions to form TRIOSE BISPHOSPHATE.
• Glycolysis- STAGE 4. What is formed?


  DEHYDROGENATION- Triose bisphosphate is then oxidized to form 2 Pyruvate molecules. The H+ ions are accepted by NAD molecules to form 2 NADH. 4 ATP is also produced using phosphate groups of Triose Bisphosphate.
• What type of phosphorylation is glycolysis?


  Substrate-level phosphorylation (No ETC)
• Where does the Link Reaction occur? (oxidative decarboxylation)


  The mitochondrial matrix
• How does pyruvate enter the mitochondrial matrix


  Active transport through specific carrier proteins
• Link Reaction-STAGE 1


  DECARBOXYLATION- carbon dioxide is removed
• Link Reaction- STAGE 2


  OXIDATION- hydrogen is removed and is accepted by NAD to form NADH.
• Link Reaction- What is formed and what binds with the product?


  After carboxylation and oxidation, ACETYL group is formed and binds with coenzyme A -> Acetyl coenzymeA
• What does Acetyl CoA do?


  Delivers acetyl group to the next stage of aerobic respiration. (Krebs cycle)
• Where does the Krebs cycle take place?


  mitochondrial matrix
• Krebs Cycle (Citric Acid Cycle)- STAGE 1


  Acetyl group (2C) binds with Oxaloacetate (4C) to form Citrate (6C)

  
• Krebs Cycle- STAGE 2


  Citrate undergoes decarboxylation (releases CO2) and dehydrogenation (releases H+ which is accepted by NAD to form NADH). A 5C compound is produced as a result.
• Krebs Cycle- STAGE 3


  The 5C compound undergoes further decarboxylation (releases CO2) and further dehydrogenation (releases H+ which is accepted by NAD to form NADH). Eventually, Oxaloacetate (4C) is formed/regenerated.
• Krebs Cycle- STAGE 4


  ATP is produced by substrate level phosphorylation.

  FAD is reduced -> FADH2

  NAD is reduced -> NADH
• Products of Krebs Cycle of a glucose molecule (2 cycles)


  2 ATP, 6 NADH, 2 FADH2, 4 CO2
• Importance of coenzymes in cellular respiration


  Coenzymes are required to transfer protons, electrons and functional groups. Coenzymes are organic molecules that bind loosely to the active site of an enzyme.
• Name the 2 types of coenzymes involved in cellular respiration


  NAD and FAD
• Differences between NAD and FAD


  - NAD takes part in all stages of respiration, FAD only in Krebs- NAD accepts 1 hydrogen + 2 electrons, FAD accepts 2 hydrogens and 2 electrons-reduced NAD is oxidised at the start of the ETC whilst FAD is oxidised further along the chain - reduced NAD results in synthesis of 3 ATP, FAD only 2
• Where does oxidative phosphorylation occur?


  inner mitochondrial membrane (membranes of cristae)
• Oxidative Phosphorylation


  The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.

  
• Oxidative Phosphorylation- STAGE 1


  NADH and FADH2 collected during the process dissociate into H+ ions and electrons.
• Oxidative Phosphorylation- STAGE 2


  Energy is released during redox reactions as they reduce and oxidise electron carriers as they flow along the ETC. The energy pumps H+ ions into the intermembrane space creating a proton gradient.
• Oxidative Phosphorylation- STAGE 3


  The H+ ions then diffuse down the electrochemical gradient synthesising ATP using ATP synthase.
• Oxidative Phosphorylation- STAGE 4 (end)


  At the end of the ETC, the electrons combine with H+ and oxygen (FINAL ELECTRON ACCEPTOR) to form water.
• Substrate-level Phosphorylation


  The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
• Anaerobic Respiration


  No oxygen used respiration. 2 ATP is made (substrate-level phosphorylation) compared to 38 avg ATP in Aerobic Respiration
• Anaerobic Respiration- Fermentation


  Organic compounds e.g. glucose is not fully broken down. Fermentation breaks down organic compounds into simpler inorganic compounds without oxygen or ETC.
• Why does anaerobic respiration produce significantly less ATP than aerobic respiration


  Glucose is not completely broken downNo oxygen as final electron acceptor and so no ETC and no synthesis of ATP by chemiosmosis.
• What comes to a stop during anaerobic respiration?


  Krebs Cycle

  Glycolysis (if not for fermentation)

  Oxidative Phosphorylation

  NAD and FAD cannot be regenerated and accept hydrogens.
• Lactate fermentation (Mammals)- STAGE 1


  Pyruvate accepts hydrogen released from NADH.
• Lactate fermentation (Mammals)- STAGE 2. What enzyme catalyses the process of pyruvate accepting hydrogen.


  LACTATE DEHYDROGENASE.