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Ch 9: Cellular Respiration. The Big Picture Cellular respiration sole purpose is to Cellular respiration sole purpose is to produce ATP. produce ATP.

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Presentation on theme: "Ch 9: Cellular Respiration. The Big Picture Cellular respiration sole purpose is to Cellular respiration sole purpose is to produce ATP. produce ATP."— Presentation transcript:

1 Ch 9: Cellular Respiration

2 The Big Picture Cellular respiration sole purpose is to Cellular respiration sole purpose is to produce ATP. produce ATP. Its an exergonic (catabolic)reaction. Its an exergonic (catabolic)reaction. Can be summarized as a whole as: Can be summarized as a whole as: Organic Compound+Oxygen CO2+Water +ATP + heat +ATP + heat

3 Glycolysis, Krebs Cycle, and Oxidative Phosphorylation 1. Glycolysis is the decomposition of glucose to pyruvate (or pyruvic acid) 1. Glycolysis is the decomposition of glucose to pyruvate (or pyruvic acid) 2. Krebs Cycle takes pyruvate (2 pyruvate per glucose molecule) and yields electron acceptors and ATP. 2. Krebs Cycle takes pyruvate (2 pyruvate per glucose molecule) and yields electron acceptors and ATP. 3. Oxidative phosphorylation extracts ATP from NADH and FADH2. 3. Oxidative phosphorylation extracts ATP from NADH and FADH2.

4 Reminder on ATP ATP (adenosine triphosphate) is a nucleotide with unstable phosphate bonds that the cell hydrolyzes for energy. ATP (adenosine triphosphate) is a nucleotide with unstable phosphate bonds that the cell hydrolyzes for energy. The cell taps energy stored in ATP by enzy- The cell taps energy stored in ATP by enzy- matically transferring terminal phosphate matically transferring terminal phosphate groups from ATP to other compounds. groups from ATP to other compounds. The compound receiving the phosphate group is said to be phosphoralated and is more reactive as a result. The compound receiving the phosphate group is said to be phosphoralated and is more reactive as a result. Cells use ATP to continue cellular work. But they must replenish the ATP supply to continue cellular work. Respiration does this. Cells use ATP to continue cellular work. But they must replenish the ATP supply to continue cellular work. Respiration does this.

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6 Simply put – cellular respiration is a redox process that transfers hydrogen from sugar to oxygen. Valence electrons of carbon and hydrogen lose potential energy as they shift toward electronegative O. Released energy is used by cells to produce ATP.

7 Redox reactions These are the energy-shuttling mechansisms of metabolism These are the energy-shuttling mechansisms of metabolism Partial or complete gain of electrons=reduction Partial or complete gain of electrons=reduction Partial or complete loss of electron=oxidation Partial or complete loss of electron=oxidation They are always coupled…so in order for a material to lose an electron, another molecule must accept it They are always coupled…so in order for a material to lose an electron, another molecule must accept it

8 The NAD+, NADH, FAD+, FADH NAD+ and FAD+ are coenzymes that function in the redox reactions and are found in all cells. NAD+ and FAD+ are coenzymes that function in the redox reactions and are found in all cells. Traps energy-rich electrons from the organic compound. Traps energy-rich electrons from the organic compound. NAD+= oxidized coenzyme NAD+= oxidized coenzyme NADH= reduced coenzyme NADH= reduced coenzyme Why isnt glucose oxidized in one explosive step?

9 During oxydation of glucose, NAD + functions as an oxidizing agent by trapping energy-rich electrons from glucose. These reactions are catalized by enzymes called dehydrogenases which: During oxydation of glucose, NAD + functions as an oxidizing agent by trapping energy-rich electrons from glucose. These reactions are catalized by enzymes called dehydrogenases which: - Remove a pair of hydrogen atoms (2 e,2p) from substrate. - Deliver the two electrons and one proton to NAD + - Release the remaining proton into the surrounding solution.

10 Cellular Respiration

11 Glyclolysis (per glucose molecule) Takes place in cytosol. Takes place in cytosol. Mutiple steps (9 or 10 depending on source) in the process of decomposing glucose into pyruvate. Mg2+ ions are cofactors to help. Mutiple steps (9 or 10 depending on source) in the process of decomposing glucose into pyruvate. Mg2+ ions are cofactors to help. 2 ATP go IN 2 ATP go IN 4 ATP PRODUCED (so what is NET gain?) 4 ATP PRODUCED (so what is NET gain?) 2 NAD+ go IN 2 NAD+ go IN 2 NADH PRODUCED 2 NADH PRODUCED 2 Pyruvate (Pyruvic acid) PRODUCED 2 Pyruvate (Pyruvic acid) PRODUCED

12 Glycolysis………. - occurs whether O is present or not - no CO 2 is released as glucose is oxidized to pyruvate; all C in glu – cose can be accounted for in the 2 molecules of pyruvate. - occurs in 2 phases

13 Glycolysis: Energy Investment Phase - includes 5 preparatory steps in which glucose is split in two. -consumes ATP….why? The cell uses ATP to phosphorylate the intermediates of glycolysis. -End result of this phase is 2 molecules of glyceraldehyde phosphate (3 C each) for each glucose molecule.

14 Glycolysis: Energy – Yielding Phase - two 3 carbon intermediaries (PGAL) are oxidized becoming pyruvate. - theres a net gain of 2 ATPs by substrate phosphorylation - 2 molecules of NAD + are reduced to NADH

15 Breaks down Glucose (6-carbon sugar) into 2 molecules of Pyruvic Acid (3-carbon compound) Glycolysis The products are: –2 Pyruvic Acid molecules –2 ATP molecules –2 NADH molecules

16 If Oxygen is present (Aerobic)...Krebs Cycle… then to Electron Transport Chain Glycolysis has 2 pathways… If Oxygen is absent (Anaerobic) …….. Fermentationoccurs

17 KREBS Cycle (per pyruvate) Takes place in mitochondrial matrix. Takes place in mitochondrial matrix. Pyruvate combines with CoA (coenzyme A) to make acetyl CoA. This makes 1 NADH and 1 CO2. Pyruvate combines with CoA (coenzyme A) to make acetyl CoA. This makes 1 NADH and 1 CO2. Acetyl CoA combines with OAA to form citric acid. (8 steps yielding intermediate products). 3 NADH and 1 FADH2 are made and CO2 released. 1 ATP is made. Acetyl CoA combines with OAA to form citric acid. (8 steps yielding intermediate products). 3 NADH and 1 FADH2 are made and CO2 released. 1 ATP is made. How much total ATP then for the Krebs cycle? How much total ATP then for the Krebs cycle?

18 Junction between gly- colysis and Krebs Cycle Is the oxidation of Pyru- vate to acetyl CoA. - CO 2 is removed from the carboxyl group of pyruvate changing it from a 3 carbon to a 2 carbon compound. CO 2 is released. - 2 NADH molecules are produced - Coenzyme A attaches to the acetyl group – very unstable-reactive

19 KREBS CYCLE (Aerobic Pathway) Krebs Cycle oxidizes the remaining acetyl fragments of Acetyl – CoA to CO 2. - Energy released from this exergonic process is used to reduce co – enzymes, NAD and FAD, and phosphory – late ATP. How many ATPs are produced here? - 2 NADH molecules are produced - Coenzyme A attaches to the acetyl group – very unstable-reactive

20 ETC (Oxidative Phosphorylation) Takes place in inner mitochondrial membrane Takes place in inner mitochondrial membrane Involves a passing of electrons through a series of membrane associated electron carriers in the mitochondria to ultimately produce ATP Involves a passing of electrons through a series of membrane associated electron carriers in the mitochondria to ultimately produce ATP You shuffle electrons to pump protons across the mitochondiral membrane against a concentration gradient to help establish a proton gradient You shuffle electrons to pump protons across the mitochondiral membrane against a concentration gradient to help establish a proton gradient

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22 The ETC transports electrons from NADH and FADH2 along a transport chain The ETC transports electrons from NADH and FADH2 along a transport chain The respiratory chain is composed of 4 enzyme complexes and carriers called cytochrome c and ubiquinone (Q). The 1 st two complexes shuttle the electrons of NADH + H+ and FADH2 to Q. The respiratory chain is composed of 4 enzyme complexes and carriers called cytochrome c and ubiquinone (Q). The 1 st two complexes shuttle the electrons of NADH + H+ and FADH2 to Q. The third complex moves electrons from Q to chytochrome c. The third complex moves electrons from Q to chytochrome c. The final complex passes electrons to O 2, an ultimate acceptor, which results in H20 as a by-product The final complex passes electrons to O 2, an ultimate acceptor, which results in H20 as a by-product

23 The chain is an energy converter that pumps H+ across the membrane. How? Certain members along the electron transport chain accept and release protons along with electrons. A gradient is created that is referred to as the proton- motive force The chain is an energy converter that pumps H+ across the membrane. How? Certain members along the electron transport chain accept and release protons along with electrons. A gradient is created that is referred to as the proton- motive force Now this H+ has the capacity to do work Now this H+ has the capacity to do work

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25 The electron transport chain made no ATP directly, but it did ease the fall of electrons from food to oxygen The electron transport chain made no ATP directly, but it did ease the fall of electrons from food to oxygen So now, by chemiosmosis, it will couple this electron transport and energy release to ATP Synthase So now, by chemiosmosis, it will couple this electron transport and energy release to ATP Synthase ATP Synthase is an enzyme that catalyses ATP from ADP and an ATP Synthase is an enzyme that catalyses ATP from ADP and an inorganic phosphate Each NADH produces 3 ATP Each NADH produces 3 ATP Each FADH produces 2 ATP Each FADH produces 2 ATP

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27 To summarize, for each glucose molecule… Glycolysis makes 2 NET ATP and 2 NADH and Glycolysis makes 2 NET ATP and 2 NADH and 2 pyruvate 2 acetyl CoA = 2 NADH 2 pyruvate 2 acetyl CoA = 2 NADH Krebs Cycle: 6 NADH, 2 FADH 2, 2 ATP Krebs Cycle: 6 NADH, 2 FADH 2, 2 ATP Since each NADH produces 3 ATP during oxidative phosphorylation and each FADH 2 produces 2 ATP…how many ATP total? Since each NADH produces 3 ATP during oxidative phosphorylation and each FADH 2 produces 2 ATP…how many ATP total?

28 Wait…but what if there is no oxygen? What will be affected? Well now there is no electron acceptor to accept electrons at the end of the ETC. NADH will accumulate. Once all NAD+ has been made to NADH, Krebs and glycolysis will eventually stop. What will be affected? Well now there is no electron acceptor to accept electrons at the end of the ETC. NADH will accumulate. Once all NAD+ has been made to NADH, Krebs and glycolysis will eventually stop. We have to free NAD+ to allow glycolysis to continue! We must release some NAD+ for use by glycolysis We have to free NAD+ to allow glycolysis to continue! We must release some NAD+ for use by glycolysis

29 1.Alcoholic : Yeast & other microorganisms use this to produce alcohol & CO2 as wastes. Beer is a beverage made by alcoholic fermentation 2 TYPES: Alcoholic & Lactic Acid FERMENTATION (Aanerobic Pathway)

30 Alcoholic Fermentation Commonly done by yeast in an anaerobic environment. 1) Glycolysis is done as normal. And then, to regenerate the NAD+… 2) Pyruvate acetaldehyde 2) Pyruvate acetaldehyde 3) Acetaldehyde ethanol…the energy in NADH is used to drive this reaction and this will release NAD+. For each acetaldehyde, 1 ethanol is made and 1 NAD+ is produced. 3) Acetaldehyde ethanol…the energy in NADH is used to drive this reaction and this will release NAD+. For each acetaldehyde, 1 ethanol is made and 1 NAD+ is produced. Now we have made 2 ATP from glyocolysis for each 2 converted pyruvate Now we have made 2 ATP from glyocolysis for each 2 converted pyruvate

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32 2.Lactic Acid: –Exercise causes the body needs more oxygen for respiration to make more ATP –Body resorts to lactic acid fermentation to make ATP –Lactic Acid is also produced causing burning sensation in muscles (Aanerobic Pathway) Or…we can do Lactic Acid Fermentation

33 Lactic Acid Fermentation Commonly done by: Muscle cells during oxygen debt. Commonly done by: Muscle cells during oxygen debt. Same thing as before: Same thing as before: - do glycolysis - but then to regenerate NAD+, a byproduct called lactate is made instead of acetylaldehyde ethanol.

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35 Diagram Assignment You will diagram the major pathways to respiration in color in a way that is understandable to you. Use websites and the book to help you form diagrams for each section of respiration. You will diagram the major pathways to respiration in color in a way that is understandable to you. Use websites and the book to help you form diagrams for each section of respiration. It must be in color, complete, and have words on it to describe what is happening in the process for full credit. It must be in color, complete, and have words on it to describe what is happening in the process for full credit. Also must have an input/output chart by each stage: glycolysis, krebs, + ETC Also must have an input/output chart by each stage: glycolysis, krebs, + ETC


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