CH 01 respiration

• Cellular respiration is a series of metabolic reactions controlled by enzymes that cause the oxidation of organic compounds to release energy as ATP
• Dehydrogenation is a type of oxidation that leads to the removal of hydrogen from organic substances
• Decarboxylation is the removal of carbon from organic molecules
• Glycolysis is the oxidation of glucose to pyruvate
• Kreb’s cycle is a cyclic process controlled by enzymes involving a series of decarboxylation and dehydrogenation reactions with little production of ATP, along with reduced NAD and FAD
• Substrate level phosphorylation is the formation of ATP from ADP and phosphate ions catalyzed by enzymes, involving glycolysis and Kreb’s cycle
• Oxidative phosphorylation is the formation of ATP assisted by a membrane-associated electron-transport chain and the creation of a proton motive force
• Chemiosmosis is the generation of a proton gradient by electron transport, used to drive the synthesis of ATP by oxidative phosphorylation
• Respiratory quotient is the volume of carbon dioxide produced divided by the volume of oxygen used up during respiration
• Oxygen debt is excess oxygen that needs to be taken up after exercise to make up for the deficit incurred during exercise
• Oxygen deficit is the difference in the volume of oxygen between the ideal oxygen uptake and an actual uptake
• Metabolism refers to the sum of all chemical reactions involved in catabolism and anabolism
• Catabolic reactions are responsible for the breakdown of food to obtain energy, while anabolic reactions use the energy produced by catabolic reactions to synthesize larger molecules from smaller ones
• Catabolic reactions release energy while anabolic reactions conserve energy
• Transport of substances via active transport, metabolic reactions, locomotion, maintenance of body temperature, and muscle contraction are all processes that require energy in living organisms
• Adenosine Triphosphate (ATP) is a phosphorylated nucleotide with energy-rich pyrophosphate bonds, small in size, water-soluble, stable at cellular pH levels, and serves as an immediate energy donor
• ATP can be synthesized during glycolysis and Kreb’s cycle by substrate level phosphorylation and oxidative phosphorylation
• ATP synthesis occurs through phosphate transfer in substrate-linked reactions and chemiosmosis in mitochondrial and chloroplast membranes
• Different respiratory substrates produce varying amounts of ATP due to differences in organic structures, particularly the number of hydrogen atoms
• Respiratory Quotient (RQ) is the ratio of carbon dioxide produced to oxygen used, helping predict the respiratory substrates being used
• Mitochondria are responsible for ATP production, apoptosis, cell differentiation, growth, development, cholesterol metabolism, and detoxification of ammonia
• Mitochondrial structure features an external double membrane, inner membrane with cristae for increased surface area, matrix for enzyme activity, and intermembrane space for proton gradient generation
• Glycolysis is a process in the cytoplasm resulting in pyruvate formation, not requiring oxygen, and yielding 2 ATP, 2 pyruvate, and 2 NADH molecules
• Lactate fermentation does not involve decarboxylation, while alcoholic fermentation produces carbon dioxide in the conversion of pyruvate to ethanol
• Differences between lactate fermentation and alcoholic fermentation:

  • Lactate fermentation does not involve decarboxylation, while carbon dioxide is produced in the conversion of pyruvate to ethanol
  • Lactate fermentation is reversible in the presence of oxygen, whereas alcoholic fermentation is not
  • Lactate fermentation is a single-step reaction, while ethanol formation is a 2-step process
  • Lactate dehydrogenase is involved in lactate fermentation, whereas alcohol dehydrogenase is involved in alcoholic fermentation
• Differences between aerobic and anaerobic respiration:

  • Anaerobic respiration produces much less energy compared to aerobic respiration
  • Anaerobic respiration depletes glycogen reserves since more glucose needs to be broken down to produce the same amount of energy as aerobic respiration
  • Anaerobic respiration is 2.5 times faster than aerobic respiration
  • Anaerobic respiration produces toxic products such as lactate and ethanol, while aerobic respiration produces non-toxic products like carbon dioxide and water
• Main features of the Link reaction:

  • Occurs when oxygen becomes available in the cell and pyruvate can be transported into the mitochondria
  • Pyruvate produced after glycolysis enters the mitochondrion matrix via active transport
  • Pyruvate undergoes dehydrogenation and decarboxylation to form Acetyl Coenzyme A
  • Requires the enzyme complex pyruvate dehydrogenase complex
  • Carbon lost forms carbon dioxide
  • Dehydrogenation step produces reduced NAD (NADH)
  • Yields from each glucose molecule: 2 molecules of Acetyl Coenzyme A, 2 molecules of CO2, 2 molecules of NADH
• Main features of the Krebs cycle:

  • Occurs in the mitochondrial matrix after the Link reaction
  • Begins with Acetyl Coenzyme A from the Link Reaction
  • Acetyl Coenzyme A combines with oxaloacetate to produce citric acid
  • Citric acid undergoes decarboxylation and dehydrogenation to produce α-ketoglutararte
  • α-ketoglutararte undergoes additional decarboxylation and dehydrogenation to reproduce oxaloacetate
  • Energy released from dehydrogenation reactions used to reduce electron carriers NAD+ and FAD+ to produce NADH and FADH2 and produce ATP
• • Produces: 4 molecules of carbon dioxide, 2 molecules of ATP, 6 molecules of NADH, 2 molecules of FADH2
• Steps of Oxidative Phosphorylation:

  • Electron carrier donates high energy electrons to the first protein in the chain (complex I)
  • Oxidation and reduction of protein chains and other molecules in the electron transport chain
  • High energy electrons transported lose energy in redox reactions
  • Energy used to transfer protons across the inner membrane to create an electrochemical gradient
  • Protons travel back into the matrix via ATPase to form ATP
  • Oxygen acts as the final electron acceptor to produce water
  • 1 NAD produces 3 ATP and 1 FAD produces 2 FADH
• • Yield: 10 NADH = 30 ATP, 2 FADH = 4 ATP
• Role of NAD+ in respiration:

  • Coenzyme acting as a hydrogen carrier
  • Carries protons and electrons produced in glycolysis, Link reaction, and Krebs cycle to the ETC
  • Oxidizes triose phosphate to pyruvate in glycolysis by accepting H
  • Gets oxidized in the ETC, indirectly providing energy for ATP synthesis
  • Proton combines with oxygen to form water
• What happens to the body during exercise:

  • Blood vessels in muscles dilate to increase blood flow and oxygen supply
  • Aerobic breakdown of pyruvic acid may become insufficient, leading to anaerobic respiration
  • ATP produced by mechanisms like anaerobic respiration, oxymyoglobin, and creatine phosphate
  • Heart and lungs increase function to meet oxygen demand
  • Oxygen debt repaid by increased heart rate and breathing
• Factors contributing to oxygen debt:

  • Removal of lactate
  • Replenishment of Phosphocreatine in muscles
  • Restoration of blood oxygen
  • Elevation of body temperature
  • Elevation of hormones
  • Increase in heart rate and breathing after exercise
• Adaptations of rice to flooded fields:

  • Aerenchymal tissue in leaves and stems allows oxygen to reach roots
  • Ridges on leaf underside trap air around the leaf
  • Roots respire anaerobically with high levels of alcohol dehydrogenase for ethanol tolerance
• Temperature changes and rate of respiration:

  • Temperature increase enhances cellular respiration until enzymes denature at extreme temperatures
• Investigations determining effect of limiting factors on rate of respiration:

  • Effect of temperature on yeast respiration using methylene blue
  • Effect of substrate concentration on respiration by adding different substrate concentrations to yeast cells
  • Controlling variables like volume of dye, yeast suspension, type and concentration of substrate, and temperature