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Cellular Respiration      Dr. Mark A. McGinleyHonors College and Department of       Biological Sciences      Texas Tech U...
Biological Work• Most of the energy used to do biological work  comes from ATP• ATP breaks down and releases energy that i...
Energetics in a Nutshell• Photosynthesis converts light energy to  potential energy stored in chemical bonds of  glucose• ...
Breaking Down Glucose to Release           Potential Energy• Starts with the process of glycolysis• Followed by either  – ...
Glycolysis• Glucose broken down into two molecules of  pyruvate  – Occurs in the cytosol• Breaking down ATP requires the i...
Glycolysis• Glucose + 2ATP => 2 pyruvate + 4 ATP + H+
Glycolysis• Glycolysis breaks down glucose to release  energy in two ATPs  – ATPs can release energy to do biological work
Problem Facing the Cell• Glucose <= => 2 pyruvate + H+• This reaction will continue to break down  glucose to release ATP ...
Solution• In order to allow glycolysis to continue cells  must maintain the concentration gradient by  removing pyruvate a...
Ultimate Solution• H+ must be removed from NADH in order to  allow glycolysis to continue• Key Point- How this happens dep...
Anaerobic Environment• When there is no oxygen in the environment  then pyruvate and H+ are removed from the  cell by ferm...
Alcohol Fermentation• Pyruvate and H+ => acetaldehyde => ethanol• Ethanol becomes the ultimate “hydrogen  acceptor”
Advantages and Disadvantages of        Alcohol Fermentation• Benefit  – End products of glycolysis are removed from the   ...
Lactic Acid Fermentation• Pyruvate + H+ => lactate• Lactate becomes the ultimate hydrogen  acceptor
Advantages and Disadvantages of      Lactic Acid Fermentation• Benefit  – End products of glycolysis are removed from the ...
Review in Anaerobic Environments• Glucose broken down by glycolysis and  fermentation• For each glucose molecule broken do...
Aerobic Environments• When oxygen is present  – O2 + H+ => H20• Water becomes the ultimate hydrogen  acceptor  – Benefit  ...
Energy From Pyruvate• Glycolysis occurs in the cytosol  – NADH and pyruvate move into the mitochondria• In the mitochondri...
Pyruvate Links Glycolysis and Citric            Acid Cycle
Citric Acid Cycle• The details of the Citric Acid Cycle are well know   – Not super important for this course• Key Points ...
Electron Transport• In a process very similar to what we talked  about in cyclic electron flow in photosynthesis  – An exc...
Electron Transport
Review in Aerobic Environments• Glucose broken down by glycolysis, citric acid  cycle, and electron transport• For each gl...
Advantages of Breaking Down Glucose      in Aerobic Environments• Benefit  – End products of glycolysis are removed from t...
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Cellular respiration

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Transcript of "Cellular respiration"

  1. 1. Cellular Respiration Dr. Mark A. McGinleyHonors College and Department of Biological Sciences Texas Tech University
  2. 2. Biological Work• Most of the energy used to do biological work comes from ATP• ATP breaks down and releases energy that is used to do biological work
  3. 3. Energetics in a Nutshell• Photosynthesis converts light energy to potential energy stored in chemical bonds of glucose• Cellular Respiration converts potential energy in glucose to potential energy stored in ATP – ATP releases energy used to do work• Glucose links the two processes
  4. 4. Breaking Down Glucose to Release Potential Energy• Starts with the process of glycolysis• Followed by either – Fermentation (in anaerobic environments) – Citric Acid Cycle (Krebs Cycle) + electron transport (in aerobic environments)
  5. 5. Glycolysis• Glucose broken down into two molecules of pyruvate – Occurs in the cytosol• Breaking down ATP requires the input of energy from 2 molecules of ATP but releases energy in 4 molecules of ATP• Thus, net gain of energy of 2 ATPs in glycolysis
  6. 6. Glycolysis• Glucose + 2ATP => 2 pyruvate + 4 ATP + H+
  7. 7. Glycolysis• Glycolysis breaks down glucose to release energy in two ATPs – ATPs can release energy to do biological work
  8. 8. Problem Facing the Cell• Glucose <= => 2 pyruvate + H+• This reaction will continue to break down glucose to release ATP until the reaction reaches an equilibrium• Once equilibrium is reached, glycolysis will stop, so no more ATP is released
  9. 9. Solution• In order to allow glycolysis to continue cells must maintain the concentration gradient by removing pyruvate and H+ from the cell.• H+ picked up by NAD+ => NADH• Eventually NAD+ gets saturated
  10. 10. Ultimate Solution• H+ must be removed from NADH in order to allow glycolysis to continue• Key Point- How this happens depends on whether or not there is oxygen in the environment
  11. 11. Anaerobic Environment• When there is no oxygen in the environment then pyruvate and H+ are removed from the cell by fermentation• Several patterns of fermentation including – Alcohol fermentation – Lactic acid fermentation
  12. 12. Alcohol Fermentation• Pyruvate and H+ => acetaldehyde => ethanol• Ethanol becomes the ultimate “hydrogen acceptor”
  13. 13. Advantages and Disadvantages of Alcohol Fermentation• Benefit – End products of glycolysis are removed from the cell so glycolysis can continue• Disadvantage – Alcohol can be poisonous to cells – Pyruvate used to help remove H+ from the cell • Still lots of potential energy stored in pyruvate • Can’t break down pyruvate to release energy
  14. 14. Lactic Acid Fermentation• Pyruvate + H+ => lactate• Lactate becomes the ultimate hydrogen acceptor
  15. 15. Advantages and Disadvantages of Lactic Acid Fermentation• Benefit – End products of glycolysis are removed from the cell so glycolysis can continue• Disadvantage – lactate can be poisonous to cells – Pyruvate used to help remove H+ from the cell • Still lots of potential energy stored in pyruvate • Can’t break down pyruvate to release energy
  16. 16. Review in Anaerobic Environments• Glucose broken down by glycolysis and fermentation• For each glucose molecule broken down there is a net gain of two ATPs
  17. 17. Aerobic Environments• When oxygen is present – O2 + H+ => H20• Water becomes the ultimate hydrogen acceptor – Benefit • Water is non-toxic and in fact is beneficial • Pyruvate can be broken down to release more stored energy
  18. 18. Energy From Pyruvate• Glycolysis occurs in the cytosol – NADH and pyruvate move into the mitochondria• In the mitochondria pyruvate is broken down to release ATP in two processes – Citric acid cycle (Krebs Cycle) – Electron transport
  19. 19. Pyruvate Links Glycolysis and Citric Acid Cycle
  20. 20. Citric Acid Cycle• The details of the Citric Acid Cycle are well know – Not super important for this course• Key Points – Inside of the mitochondrion pyruvate breaks down to produce CO2 + Acetyl CoA – Acetyl CoA enters Citric Acid Cycle • Acetyl CoA + oxaloacetate = > citrate – CO2 released – 1 ATP produced for each Acetyl CoA that enters the cycle • Thus, 2 ATPs per glucose
  21. 21. Electron Transport• In a process very similar to what we talked about in cyclic electron flow in photosynthesis – An excited electron moves down an electron transport chain (located in inner membranes of mitochondria) • Energy released used to actively transport H+ • H+ concentration gradient powers Chemiosmosis – Releases lots of ATP – 26 or 28 ATP/glucose
  22. 22. Electron Transport
  23. 23. Review in Aerobic Environments• Glucose broken down by glycolysis, citric acid cycle, and electron transport• For each glucose molecule broken down there is a net gain of 30 - 32 ATPs – 2 per glucose from glycolysis – 2 per glucose from citric acid cycle – 26 – 28 per glucose from electron transport
  24. 24. Advantages of Breaking Down Glucose in Aerobic Environments• Benefit – End products of glycolysis are removed from the cell so glycolysis can continue – Ultimate hydrogen acceptor (water) is beneficial to cells – Pyruvate can be broken down to release much more energy
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