Cellular Respiration and Anaerobic Respiration

• aerobic respiration


  catabolic pathways that require oxygen

  
• What does cellular respiration equation represent?

  2 dozen reactions that occur in different parts of the cell

  
• The processes of cellular respiration

  1. Glycolysis

  2. Pyruvate oxidation

  3. Krebs cycle

  4. Oxidative phosphorylation

  
• Glycolysis

  metabolic pathway in the cytoplasm that breaks down glucose into pyruvate, starts with glucose and the products are 2 pyruvate, 2 NADH, and 2 ATP

  
• Pyruvate oxidation

  Conversion of 2 pyruvate, 2 NAD+, and 2 CoA to 2 acetyl CoA, 2 CO2 and 2 NADH that occurs in the mitochondrial matrix in the presence of O2

  
• Krebs cycle

  occurs in the mitochondrial matrix to convert 2 acetyl-CoA, 6 NAD+, 2 FAD, 2 CoA, 2 GDP, 2 Pi, 2 ADP, and 2H2O to 2 ATP, 6 NADH, 2 FADH2, 2 oxaloacetate, 2 GTP, 4 CO2, and 4 CoA

  
• oxidative phosphorylation

  when FADH2 and NADH oxidize and transport their electrons in the inner mitochondrial membrane and produce 32 ATP (eukaryotes) or 34 ATP (prokaryotes)

  
• Phosphorylation

  the addition of a phosphate group to a molecule

  
• substrate-level phosphorylation

  when a phosphate group is transferred from a substrate to ADP to form ATP

  
• Step 1 of Glycolysis

  glucose enters the cell and receives a phosphate group from ATP as it breaks down into ADP and forms glucose-6-phosphate with the help of hexokinase

  
• Step 2 of glycolysis

  glucose-6-phosphate is rearranged into fructose-6-phosphate by forming new links between oxygen and the 2nd carbon, assisted by phosphoglucomutase (isomerization)

  
• Step 3 of glycolysis

  ATP breaks down into ADP and an inorganic phosphate (Pi) and the inorganic phosphate group bonds with 1st carbon of fructose-6-phosphate with the help of phosphofructokinase to form fructose-1,6-bisphosphate

  
• step 4 of glycolysis

  fructose-1,6-bisphosphate is worked on by aldolase to be separated into 2 three carbon chains called glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP)

  
• step 5 of glycolysis

  DHAP is isomerized with the help of triphosphate isomerase into glyceraldehyde-3-phosphate (G3P), making 2 G3P molecules in total

  
• step 6 of glycolysis

  NAD+ reduces into NADH as it gains 2 electronsn, glyceraldehyde-3-phosphate (G3P) releases a H+ ion and gains an inorganic phosphate group from the cytoplasm with the help of triosephosphate dehydrogenase, forming two molecules of 1,3-bisphosphoglycerate

  
• Step 7 of glycolysis

  1,3-bisphosphoglycerate releases the inorganic phosphate from the 1st carbon to ADP to form ATP with the help of phosphoglycerate kinase, resulting in 2 molecules of 3-phosphoglycerate

  
• Step 8 of Glycolysis

  3-phosphoglycerate uses phosphoglucomutase to catalyze the transfer of the phosphate group from the 3rd to 2nd carbon, forming 2 molecules of 2-phosphoglycerate

  
• Step 9 of glycolysis

  2-phosphoglycerate is worked on by enolase to remove the hydroxyl group from the 3rd carbon and hydrogen from the 2nd carbon to form 2 molecules of phosphoenolpyruvate (PEP) which is a precursor to pyruvate

  
• Step 10 of Glycolysis

  phosphoenol pyruvate gets rid of a phosphate group resulting in 2 molecules of pyruvate, and the phosphate group attaches to ADP, forming ATP, pyruvate kinase catalyzes this reaction

  
• Location of glycolysis

  cytoplasm
• reactant of glycolysis

  1 glucose, 2 ATP, 2 NAD+, 4 ADP
• products of glycolysis

  2 pyruvate, 4 ATP, 2 NADH, 2H+
• ATP required for glycolysis


  2
• ATP produced in glycolysis

  4 (net 2)
• Anoxic


  no oxygen

  
• Anaerobic respiration


  respiration in which the final electron acceptor is not oxygen

  
• What do anaerobic organisms use?

  sulfate, nitrate, and carbon dioxide
• Similarity between aerobic and anaerobic respiration

  they both use the electron transport chain to generate a H+ concentration gradient to provide energy for phosphorylation
• facultative anaerobes


  can live with or without oxygen
• E. coli respiration

  NO3-(aq) + 2e- + 2H+ -> NO2-(aq) + H2O(l)
• Methanogen respiration

  4H2(aq) + CO2(aq) -> CH4(g) + 2H2O(l)
• Fermentation

  process in which NADH transfers its electrons to an organic acceptor molecule

  
• Reasons for fermentation

  single-celled organisms which only use glycolysis to obtain energy; not enough oxygen available to be the final electron acceptor
• 2 types of fermentation

  ethanol fermentation and lactate fermentation
• Lactate fermentation


  fermentation in animal cells in which NADH transfers hydrogen to pyruvate, forming lactate and regenerating NAD+

  
• example of lactate fermentation


  doing strenuous exercise, ATP is in demand and exceeds the rate of O2 production and the circulatory system can only provide a limited amount of O2 in the moment. leads to muscles burning from lactic acid production. after exercise, lactate is oxidized back to pyruvate and aerobic respiration resumes
• ethanol fermentation

  when NADH transfers hydrogen to acetaldehyde, forming carbon dioxide and ethanol while regenerating NAD+

  
• example of ethanol fermentation

  baking, yeast organisms consume sugar in the dough producing carbon dioxide and ethanol, leaving tiny holes in the dough
• Products of fermentation

  baked goods, alcoholic drinks, acetone, butanol, fuel
• oxidative phosphorylation


  coupling of NADH and FADH2 oxidation with ATP synthesis