Cellular Respiration Lecture 07 1 Objectives At the end of this - PDF document

22 ‐ Feb ‐ 20 Cellular Respiration Lecture 07 1 Objectives  At the end of this series of lectures, you should be able to:  Define terms.  Explain how breathing and cellular respiration are related.  Provide the overall chemical equation for cellular respiration.  Explain how the energy in a glucose molecule is released during cellular respiration. 2 1

22 ‐ Feb ‐ 20 Objectives  List the cellular regions where glycolysis, the citric acid cycle, and oxidative phosphorylation occur.  Compare the reactants, products, and energy yield of the three stages of cellular respiration.  Compare the reactants, products, and energy yield of alcohol and lactic acid fermentation. 3 Energy for Life  Most energy for life is captured as solar energy by photosynthesis.  For most organisms that energy is converted to the usable form (ATP) by cellular respiration. 4 2

22 ‐ Feb ‐ 20 Mikael Häggström, CC BY ‐ SA 3.0, http://en.wikipedia.org/wiki/Cellular_respiration#mediaviewer/File:Auto ‐ and_heterotrophs.png 5 6CO � � 12H � O � Light → C � H �� O � � 6O � � 6H � O C � H �� O � � 6O � → 6CO � � 6H � O � 32 ATP � Heat 6 3

22 ‐ Feb ‐ 20 Respiration  Breathing  inspiration (bringing air in)  expiration (moving air out)  External respiration  Internal respiration  Cellular respiration 7 𝐷 � 𝐼 �� 𝑃 � � 6 𝑃 � → 6 𝐷𝑃 � � 6 𝐼 � 𝑃 � 32 𝐵𝑈𝑄 � ℎ𝑓𝑏𝑢 8 4

22 ‐ Feb ‐ 20 Overview Concepts  Glucose can be burned and the energy released.  Not biologically useful.  Cellular respiration is the controlled release of energy from glucose.  Some of the energy is captured in a biologically useful way.  Movement of electrons in oxidation ‐ reduction (redox) reactions. 9 Overview Concepts  Oxidation ‐ Reduction Reactions  Oxidation – The loss of electrons from a substance  Reduction – The addition of electrons to a substance  These reactions occur in pairs  One reaction donates the electrons and the other accepts the reactions.  In biological reactions, you cannot see the electrons, but you can see hydrogen move which represents electron transfers. 10 5

22 ‐ Feb ‐ 20 Cameron Garnham, CC BY ‐ SA 3.0, http://commons.wikimedia.org/wiki/File:Redox_Reminder.png 11 Overview Concepts  NADH Coenzymes  NAD + accepts electrons and becomes reduced NADH  Moves electrons in a controlled manner from one reaction to another. 12 6

22 ‐ Feb ‐ 20 Overview Concepts  Electron Transport Chains  Electron transport chains are a series of carrier molecules that accept the electrons and move them down an energy gradient in a controlled fashion.  The movement of the electrons causes H + to be pumped one side of the membrane to the other. This creates a gradient of H + . The movement of H + back across the membrane is used to synthesize ATP.  O 2 is the final electron acceptor – makes H 2 O 13 Cellular Respiration  Stages  Glycolysis  Pyruvate Oxidation and Citric Acid Cycle (Krebs Cycle)  Oxidative phosphorylation (Electron Transport Chain) 14 7

22 ‐ Feb ‐ 20 OpenStax College, CC BY 3.0, http://cnx.org/contents/9d68abf9 ‐ 4c2e ‐ 4ef7 ‐ 88d1 ‐ c963c5c844b9@3 15 Cellular Respiration  Glycolysis  Occurs in the cytoplasm (cytosol)  Breaks (lyses) glucose into 2 3 ‐ carbon compounds – pyruvate.  Requires an investment of ATP  Produces 2pyruvate, 2 ATP and 2 NADH 16 8

22 ‐ Feb ‐ 20 Biology by OpenStax College is licensed under a Creative Commons Attribution 3.0 17 Glycolysis Glucose (C6) + 2 ADP + 2 Pi + 2 NAD+ → 2 ATP + 2 NADH + 2 Pyruvate (C3) 18 9

22 ‐ Feb ‐ 20 Cellular Respiration  Glycolysis  Substrate level phosphorylation  One method by which ATP is formed  Occurs in other reactions also  Passes a phosphate directly to ADP to form ATP  Requires appropriate enzyme 19 Cellular Respiration  Pyruvate Oxidation  Occurs in the matrix of the mitochondria  Breaks the pyruvates into 2 ‐ carbon compound (Acetyl CoA).  Requires coenzyme A (CoA)  Produces CO 2 – waste product  Produces 2 Acetyl CoA and NADH 20 10

22 ‐ Feb ‐ 20 Biology by OpenStax College is licensed under a Creative Commons Attribution 3.0 21 Pyruvate Oxidation 2 Pyruvate (C3) + 2 O2 + 2 NAD+ + 2 CoA → 2 CO2 + 2 NADH + 2 Acetyl CoA (C 2 ) 22 11

22 ‐ Feb ‐ 20 Cellular Respiration  Citric Acid Cycle  Also called the Krebs Cycle  Occurs in the matrix of the mitochondria  Completes the breakdown of glucose (Acetyl CoA) into CO 2 ‐‐ waste product  Produces 2ATP, 6NADH, and 2FADH 2 from each glucose (2 turns of the cycle) 23 Cellular Respiration Citric Acid Cycle 2 Acetyl CoA + 4 O2 + 6 NAD+ + 2 ADP + 2 Pi + 2 FAD+2 → 4 CO2 + 6 NADH + 2 ATP + 2 FADH2 24 12

22 ‐ Feb ‐ 20 Biology by OpenStax College is licensed under a Creative Commons Attribution 3.0 25 Cellular Respiration  Oxidative Phosphorylation  Occurs on the cristae of the mitochondria  Accepts electrons from NADH and FADH 2  Produced in glycolysis, pyruvate oxidation, and citric acid cycle.  Uses electron transport chains to generate ATP  Produces ~28 ATP 26 13

22 ‐ Feb ‐ 20 Cellular Respiration  Oxidative Phosphorylation  Chemiosmosis  Uses energy stored in a hydrogen ion gradient to drive ATP synthesis.  Occurs on the cristae of the mitochondria. 27 Cellular Respiration Oxidative Phosphorylation 7 O2 + 28 ADP + 28 Pi + 10 NADH + 2 FADH2 → 28 ATP + H2 O + 10 NAD+ + 2 FAD+2 28 14

22 ‐ Feb ‐ 20 Fvasconcellos, Public Domainhttp://en.wikipedia.org/wiki/Oxidative_phosphorylation#mediaviewer/File:Mitochondrial_electron_transport_chain%E2%80%94Etc4.svg 29 Cellular Respiration  Each glucose molecule results in the production of about 32 ATP.  Glycolysis: 2 ATP  Citric Acid Cycle: 2 ATP  Oxidative Phosphorylation: 28 ATP  About 34% of the glucose’s potential energy 30 15

22 ‐ Feb ‐ 20 Anaerobic Respiration  Fermentation  Occurs in the absence of oxygen  Glycolysis does not require oxygen so it can still produce its 2 ATP per glucose.  Need to regenerate NAD + to continue accept electrons  Other steps in cellular reaction require oxygen so they will not occur without oxygen.  Reduced efficiency 31 Anaerobic Respiration  Lactic Acid Fermentation  A process for regenerating NAD +  Occurs in muscle cells and certain bacteria  Pyruvate is converted to lactate (lactic acid)  Lactate is carried via the blood to the liver where, if there is enough oxygen, it is converted back to pyruvate.  Bacteria are use this technique to produce yogurt, cheese, soy sauce, and sauerkraut. 32 16

22 ‐ Feb ‐ 20 Darekk2, CC BY ‐ SA 3.0, http://en.wikipedia.org/wiki/Cellular_respiration#mediaviewer/File:Cellular_respiration.gif 33 Anaerobic Respiration  Alcohol Fermentation  A process for regenerating NAD +  Occurs with some yeast (fungi)  Pyruvate is converted to CO 2 and ethanol  Ethanol is toxic 34 17

22 ‐ Feb ‐ 20 Darekk2, CC BY ‐ SA 3.0, http://en.wikipedia.org/wiki/Cellular_respiration#mediaviewer/File:Cellular_respiration.gif 35 Other Metabolic Pathways  Other organic molecules can be used as fuel for cellular respiration.  Other macromolecules enter cellular respiration at different points.  Fats generate more ATP than an equal mass of carbohydrates.  Proteins produce relatively little ATP  Produces more waste (amine groups) – disposed of by urine 36 18