Cellular Respiration

1. Cellular Respiration Biology 11 E. McIntyre http://fusionanomaly.net/mitochondria.html

2. Cellular Respiration • Cellular respiration is… The process by which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen. Aerobic respiration can be summarized by the following formula: C6H12O6 + 6O2 6H20 + 6CO2 + energy (36 ATP)

3. Activation Energy • Each of the many chemical reactions that occur in cellular respiration are catalyzed by an enzyme. Enzymes are proteins that kick start chemical reactions thus lowering the activation energy required.

4. Glycolysis • Glycolysis is the first stage of cellular respiration. • Glycolysis has two parts; Glycolysis I & Glycolysis II. In order to ‘kick-start’ glycolysis I, activation energy is required (ATP). Sugar is split into two PGAL’s. In glycolysis II, PGAL is oxidized and ATP is produced. The overall pathway gets its name from this sugar splitting (glyco = sugar, lysis = split). • Glycolysis occurs in the cytosol (The fluid portion of the cytoplasm, outside the organelles).

5. An overview of Aerobic Cellular Respiration Can you find Glycolysis?

6. Coenzyme • A substance that enhances or is necessary for the action of enzymes. They are generally much smaller than enzymes themselves. NAD+ (Nicotinamide adenine dinucleotide) is a coenzyme that serves as an electron carrier.

7. Glycolysis I Glucose 6-C 1 • Glycolysis I is a series of endergonic reactions • 1.Glucose enters the cell by diffusion • 2. ATP donates a phosphate to the substrate. (1 ATP used) Glucose-6-phosphate is produced. • 3. Glucose-6-phosphate is rearranged to fructose-6-phosphate (another 6-C sugar) • 4. another ATP donates its phosphate (1 ATP used). Fructose 1,6-bisphosphate is produced. • 5. The fructose 1,6 bisphosphate molecule is split into 2 PGALs, a 3-carbon compound. Remember PGAL from photosynthesis? ATP 2 ADP Glucose ~P “glucose-6-phosphate” 6-C, 1 Phosphate 3 Fructose~P “fructose-6-phosphate” 6-C, 1 Phosphate ATP 4 ADP P~ Fructose ~P “Fructose 1,6-bisphosphate” 6-C, 2 Phosphates • **Glycolysis I …** • 2 ATP (2 ATP’s are used.) • PGAL • AKA G3P • PGAL • AKA G3P • (3-C, 1 phosphate) 5 X2 Animation

8. Glycolysis II • PGAL • (3-C, 1 phosphate) • In Glycolysis II, each PGAL (2 from 1 molecule of glucose) is oxidized to release energy. This process is exergonic. • NAD+ takes electrons from PGAL (NADH is formed). As this occurs, PGAL accepts a Pi from the cytosol. 1,3 bisphosphoglyerate (1,3 BPG) is formed • ADP removes a phosphate from the substrate and thus changes to ATP. 3-phosphoglycerate(3-PGA) is formed. • 3-phosphoglycerate is rearrangedto 2-phosphoglycerate which is then rearranged to phosphoenolpyruvate (PEP). Water is given off in this process. • PEP gives a phosphate to ADP to make ATP. Pyruvate (AKA Pyruvic acid) is formed. NAD+ Pi 1 NADH • 1,3 bisphosphoglycerate (1,3 BPG) • (3-C, 2 phosphates) ADP 2 ATP • 3-phosphoglycerate (3-PGA) • (3-C, 1 phosphate) • 2-phosphoglycerate • (3-C, 1 phosphate) X2 3 H2O phosphoenolpyruvate (PEP) ADP • **Glycolysis results in a net gain of …** • 2 ATP (2 ATP’s are used and 4 are produced) • 2 NADHThese hydrogens are transported to the mitochondria for more ATP production ATP 4 • Pyruvate (Pyruvic Acid) • (3-C, 0 phosphates) Animation

9. Substrate Level Phosphorylation • The direct phosphate transfer of phosphate from an organic molecule to ADP. IMPORTANT!

10. Think Together! Partners `A` and `B` take turns answering the questions below. A. What is the basic difference between Glycolysis I and Glycolysis II? B. What is the role of NAD+?

11. Vocabulary GAME! • Glucose • PGAL • Pyruvate • phosphate • Glucose-6 phosphate • NADH • ADP • endergonic

12. Circle the end products of glycolysis. Where do they go next?

13. Pyruvate Oxidation (Pyruvic Acid Oxidation) Pyruvate (pyruvic acid) (3-C) 1 NAD+ Remember, in glycolysis, glucose was oxidized to 2 pyruvate molecules. Therefore, the above biochemical pathways run twice for every molecule of glucose! Pyruvate Oxidation ONLY HAPPENS IF O2 is present! NADH CO2 in matrix Pyruvate Oxidation Acetate (Acetic acid ) (2-C) 1. The two pyruvates from glycolysis diffuse into the mitochondrion’s matrix. Here, NAD+ removes electrons from pyruvate. (NADH is formed). The pyruvates also lose a carbon in the form of CO2 . The remaining compound is called acetate, a 2-carbon compound. 2. Acetate combines with coenzyme A to form acetyl coenzyme A. 2 Coenzyme A (or ‘CoA’) acetyl coenzyme A (or ‘acetyl coA’) X2 Animation • **Pyruvate Oxidation results in a net gain of …** • 2 NADH. These hydrogens are transported to the Electron Transport Chain for more ATP production

14. Pyruvate Oxidation

15. Stop & Think! • What waste product is expelled from your body via the lungs? Where does this waste product come from?

16. Can you find Pyruvate oxidation? Where does it occur?

17. Animation acetyl coenzyme A (or ‘acetyl coA’) KrebsCycle Coenzyme A (or ‘CoA’) 1 8 Oxaloacetate(4-C) Citrate(6-C) • Acetyl coenzyme A enters the Krebs cycle and combines with a 4-carbon acceptor molecule. citrate (6-C) is formed. Coenzyme A is recycled for further use. • Citrate is rearranged to isocitrate (6-C) • NAD+ accepts hydrogens from isocitrate. One molecule of CO2 is given off as isocitrate loses one carbon. α-ketoglutarate (5-C) is formed. • NAD+ accepts hydrogens from α -ketoglutarate (5-C) . A CO2 is removed, coenzyme A is added, and 2 hydrogen atoms reduced NAD+ to NADH. Succinyl Co-A is produced. • Succinyl Co-A (4-C) is converted to succinate (4-C). A Pi from the matrix displaces Co-A from succinyl Co-A. The phosphate is then transferred to ADP to make ATP. You do not need to memorize all the chemical names! NADH 2 NAD Isocitrate(6-C) malate(4-C) 7 X2 H20 NAD 3 NADH CO2 fumarate(4-C) fumarate(4-C) α -ketoglutarate(5-C) 6 Co-A CO2 FADH2 Co-A FAD Succinate (4-C) 5 NAD 4 Succinyl-CoA(4-C) NADH ADP ATP Pi

18. Animation acetyl coenzyme A (or ‘acetyl coA’) KrebsCycle Coenzyme A (or ‘CoA’) 1 8 Oxaloacetate(4-C) Citrate(6-C) 6.FAD removes electrons from succinate (4-C) is produce fumarate (4-C). FADH2 is produced. 7.Fumarate (4-C) is converted to malate (4-C). 8. NAD+ removes electros from malate … oxaloacetate (4-C). Is regenerated!!! NADH is produced. Only 2 ATP’s have been produced from Krebs cycle.  NADH 2 NAD Isocitrate(6-C) malate(4-C) 7 X2 H20 NAD 3 NADH CO2 fumarate(4-C) α ketoglutarate(5-C) 6 Co-A CO2 FADH2 Co-A FAD Succinate (4-C) 5 NAD 4 Succinyl-CoA(4-C) NADH Final products of Krebs Cycle per molecule of glucose: 3 x 2 = 6 NADH  (to electron transport chain to make ATP) 1 x 2 = 2 FADH2 (to electron transport chain to make ATP) 1 x 2 = 2 ATP ATP ADP Pi

19. Think Together! • Why is there a “X2” on the diagram of the Krebs Cycle? • Krebs cycle only yields 2 ATP per molecule of glucose, but it also results in 6 NADH and 2 FADH2 produced. What do you think NADH and FADH2 is for?

21. Oxidative Phosphorylation (Electron Transport Chain) Animation #1 Animation #2 • The electron transport chain is located on the inner membrane of the mitochondrion. It consists of several electron carriers which accept electrons from NADH and FADH2 (from glycolysis and Krebs cycle). It requires O2!

22. …Oxidative Phosphorylation (Electron Transport Chain) Animation #1 Animation #2 2 1 • [1] Energized electrons from Glycolysis and Krebs cycle are carried to the electron transport chain via NADH... • [2] ...and FADH2

23. …Oxidative Phosphorylation (Electron Transport Chain) 3 4 Animation #1 Animation #2 2 1 Cytochrome bc1 complex (H+ pump) • [3]Electrons are passed through a series of electron carriers which become reduced/oxidized as they pass off the electrons [complexes I -IV]. At different places along this chain, the energy released from the electrons is used to ‘pump’ protons (H+) across the inner membrane of the mitochondrion into the intermembrane space • [4] This creates a concentration gradient in the intermembrane space.

24. …Oxidative Phosphorylation (Electron Transport Chain) 3 4 Animation #1 Animation #2 7 5 6 2 1 Cytochrome bc1 complex (H+ pump) • [5]The H+ ions are allowed to pass back into the matrix through ATP synthase. • [6]Using the energy from the flow of protons, ADP is united with Pi to form ATP. • Note that because NADH and FADH2 enter the electron transport chain at different locations, • they yield different amounts of ATP; NADH yields 3 ATP and FADH2 yields 2 ATP. • [7] The electrons unite with protons (H+) and oxygen at the end of the ETC to form water. • If insufficient O2 is available in the cell, the ETC will not work! What happens then?......

25. Smokin’ Chemiosmosis & Electron Transport Animations • http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm • http://vcell.ndsu.nodak.edu/animations/etc/movie.htm

26. Can you see why FADH2 & NADH end in different ATP yields?

27. Cyanide Blocks the Electron Transport Chain • Cyanide is a poison that inhibits cytochrome oxidase activity. Why can cyanide cause death?

28. Cyanide Blocks the Electron Transport Chain • Cyanide is a poison that inhibits cytochrome oxidase activity, preventing oxygen from acting as the final electron acceptor in the electron transport chain. This disruption virtually shuts down ATP production resulting in coma and death. That is why cyanide is a poison. However, it is not poisonous to all organisms. Anaerobic bacteria, called MIT-13 actually live on cyanide – they use it the same way aerobes use oxygen.

29. Summary of Aerobic Cellular Respiration

31. Structural Formula of ATP

32. Summary of Aerobic Cellular Respiration • Label the diagram

33. Summary of Aerobic Cellular Respiration

34. Net Energy Yield of Aerobic Respiration Huh?! A B C D E F G H I J K L M N O P Q R S T