1. Cellular Respiration Chapter 9

2. The link between Photosynthesis and Cellular Respiration Like a rechargeable battery, your body runs low on energy and needs to be supplied with more You get energy from food The energy in your food was captured from sunlight by photosynthesis Together photosynthesis and cellular respiration form a cycle

4. Overview of Cellular Respiration An introduction to the steps of cellular respiration

5. Cellular Respiration Is the complex process where cells make adenosine triphosphate (ATP) by breaking down organic compounds

6. Using Chemical Energy to Drive Metabolism Plants, algae, & some bacteria harvest energy of sunlight through photosynthesis Autotrophs: (self-feeders) are organisms that use energy from sunlight or from chemical bonds in inorganic substances to make organic compounds Basically: they get their energy from the sun, mostly through photosynthesis

7. Autotrophs vs Heterotrophs Heterotrophs (fed by others) are animals and other organisms that must get energy from food instead of directly from sunlight 95% of organisms on Earth are heterotrophs

8. So, Both Heterotrophs and Autotrophs Undergo cellular respiration to break these organic compounds into simpler molecules and release energy. Some of the energy is used to make ATP. The energy is then used by cells to do work.

9. Cellular Respiration can be divided into 2 stages: 1. Glycolysis: organic compounds are converted into 3-carbon molecules of pyruvic (pie-ROO-vic) acid, producing s small amount of ATP and NADH (the electron carrier). Glycolysis is an anaerobic process because it does not require the presence of oxygen

10. Cellular Respiration can be divided into 2 stages: 2. Aerobic Respiration: if no oxygen is present in the cell ’ s environment, pyruvic acid is broken down & NADH is used to make a large amount of ATP through the process known as aerobic respiration

11. Pyruvic acid can enter other pathways If there is no oxygen present in the cells environment. The combination of glycolysis and these anaerobic pathways is called fermentation.

12. Pyruvic Acid Definition: Is the 3-carbon compound that is produced during glycolysis and needed for both the aerobic and anaerobic pathways of cellular respiration that follow glycolysis

13. Redox Reactions Many of the reactions in cellular respiration are redox Pathways require oxygen, so glucose is oxidized and oxygen is reduced The breakdown on one glucose molecule results in 38 ATP molecules

14. FYI Organisms use cellular respiration to harness energy from organic compounds Glycolysis produces a small amount of ATP Most ATP results from aerobic respiration (which is the 2 nd stage of cellular respiration

15. Equation that summarizes cellular respiration C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy (ATP)

16. Glycolysis: 1 st stage of Cellular Respiration Glycolysis: is a biochemical pathway where one 6-carbon molecule of glucose is oxidized to produce two 3- carbon molecules of pyruvic acid. catalyzed by specific enzymes All reactions of glycolysis take place in the cytosol & occur in 4 main steps

17. Glycolysis Step 1 2 phosphate groups are attached to 1 molecule of glucose forming a 6-carbon compound that has 2 phosphate groups on its ends The phosphate groups are supplied by 2 molecules of ATP which are converted into 2 molecules of ADP in the process

18. 1 6-carbon sugar diphosphate 6-carbon glucose (Starting material) 2 PP Priming reactions. Priming reactions. Glycolysis begins with the addition of energy. Two high-energy phosphates from two molecules of ATP are added to the six-carbon molecule glucose, producing a six-carbon molecule with two phosphates. ATP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19. Glucose Priming 3 reactions “ prime ” glucose by changing it into a compound that can be cleaved into 2 3-carbon phosphorylated molecules 2 of these reactions require the cleavage of ATP, so this step requires 2 ATP molecules

20. Glycolysis Step 2 The 6-carbon compound formed in step 1 is split into two 3-carbon molecules of glyceraldehyde 3-phosphate (G3P) G3P: is also (end) produced by the Calvin cycle in photosynthesis.

21. Fig. 9.6b (TEArt) 2 6-carbon sugar diphosphate PP 3-carbon sugar phosphate PP 2 Cleavage reactions. Then, the six-carbon molecule with two phosphates is split in two, forming two three-carbon sugar phosphates. 3-carbon sugar phosphate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

22. Glycolysis Step 3: The 2 G3P molecules are oxidized, & each receives a phosphate group. The product = 2 molecules of a new 3- carbon compound The oxidation of G3P is accompanied by the reduction of 2 molecules of (nicotinamide adenine dinucleotide) NAD+ to NADH

23. Fig. 9.6c (TEArt) OVERVIEW OF GLYCOLYSIS 3 PP 3-carbon pyruvate 2 NADH ATP 2 NADH ATP Energy-harvesting reactions. Finally, in a series of reactions, each of the two three-carbon sugar phosphates is converted to pyruvate. In the process, an energy-rich hydrogen is harvested as NADH, and two ATP molecules are formed. 3-carbon sugar phosphate 3-carbon pyruvate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24. Glycolysis Step 4 The phosphate groups added in step 1 & step 3 are removed from the 3-carbon compounds This reaction produces 2 molecules of pyruvic acid Each phosphate group combines with ADP to make ATP A total of 4 Phosphate groups were added in step 1 & 3 — 4 ATP are made

25. Step 4 Continued Notice that 2 ATP molecules were made in step 1, but 4 were produced in step 4. Therefore, glycolysis has a net yield of 2 ATP molecules for every molecule of glucose that is converted into pyruvic acid.

27. Glucose New 6-carbon compound 2 molecules of G3P 2 ATP 2 ADP 12 34 c-c-c-c-c-cP-c-c-c-c-c-c-PP-c-c-c c-c-c-P P-c-c-c-P c-c-c 2 Phosphate 2 NAD+ 2 NADH + 2H + 2 molecules of new 3-carbon compound 4 ADP 4 ATP 2 H 2 O 2 molecules of pyruvic acid

28. Glycolysis Video http://www.youtube.com/watch?v =x-stLxqPt6E

29. In Aerobic conditions When oxygen is present, cellular respiration continues as pyruvic acid enters the pathways of aerobic respiration

30. In Anaerobic conditions During heavy exercise, when your cells are without oxygen for a short period of time, an anaerobic process called fermentation follows glycolysis and provides a means to continue producing ATP until oxygen is available again

31. Fermentation In anaerobic conditions, some cells can convert pyrvic acid into other compounds through additional biochemical pathways that occur in the cytosol Glycolysis & these pathways regenerate NAD+ Fermentum meaning “ leaven ” or anything that causes baked goods to rise

32. The Processes of Fermentation The additional pathways do not produce ATP Without the cellular process that recycled NAD+ from NADH, glycolysis would quickly use up all the NAD+ in the cell Glycolysis would then STOP! ATP production through glycolysis would also STOP! The fermentation allows the process to continue

33. Many fermentation pathways There are many fermentation pathways They differ in terms of the enzymes that are used & the compounds that are made from pyruvic acid 2 common fermentation pathways result in the production of 1. Lactic acid 2. Ethyl Alcohol

34. 2 common fermentation pathways Lactic Acid: an enzyme that supplies energy when oxygen is scarce, they make pyruvic acid Two molecules of pyruvic acid use NADH to form two molecules of lactic acid This releases NAD + to be used in glycolysis, allowing two ATP molecules to be formed for each glucose molecule The lactic acid is transferred from muscle cells, to the liver that converts it back to pyruvic acid.

35. Lactic Acid Fermentation

36. 2 common fermentation pathways Alcoholic Fermentation 1. A CO2 molecule is removed from pyruvic acid leaving 2-C. 2. 2-H atoms are added to the 2-C to form ethyl alcohol H-atoms come from NADH & H+, regenerating NAD+ for use in glycolysis used by yeast cells and some bacteria to produce CO 2 and ethyl alcohol

37. Alcoholic Fermentation

38. NADH Pyruvate With oxygen Without oxygen Acetyl-CoA Lactate Ethanol NAD + NADH NAD + NADH CO 2 Acetaldehyde H20H20 Krebs cycle O2O2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

39. Aerobic Respiration 2 major stages: 1. Krebs cycle 2. Electron Transport Chain (chemiosmosis)

40. Where the Krebs cycle Happen In Prokaryotic Cells: the Krebs cycle takes place in the cytosol In Eukaryotic Cells: the Krebs cycle takes place in the mitochondrial matrix

41. Mitochondrial Matrix The mitochondrial matrix is the space inside the inner membrane of the mitochondrion It contains the enzymes needed to catalyze the reactions of the Krebs cycle

42. Acetyl CoA When pyruvic acid enters the mitochondrial matrix, it reacts with a molecule called coenzyme A to form acetyl coenzyme A (acetyl CoA)

43. Pyruvic acid  Acetyl CoA The acetyl part of acetyl CoA: 2-C atoms (but remember that) Pyruvic acid: 3-C atom The C-atom is lost in the conversion from pyruvic to acetyl CoA & released as CO 2 Reaction reduces a molecule of NAD+ to NADH

44. Glycolysis yields 2 molecules of pyruvic acid Pyruvic Acid Acetyl Co A c-c-c CoA CO2 NAD+ NADH + H+ c-c

45. The Krebs Cycle Is a biochemical pathway that breaks down acetyl CoA, producing CO 2, H+, & ATP The Krebs Cycle has 5 main parts All occur in the mitochondrial matrix AKA: The Citric Cycle

46. A Little Krebs Cycle History Discovered by Hans Krebs in 1937 He received the Nobel Prize in physiology or medicine in 1953 for his discovery Forced to leave Germany prior to WWII because he was Jewish

47. The Krebs Cycle: Step 1 A 2-carbon molecule of acetyl CoA combines with a 4-carbon compound, oxaloacetic (AHKS-uh-loh-uh-SEET-it) acid, to produce a 6-carbon compound, citric acid. {the reaction regenerates coenzyme A}

48. OVERVIEW OF THE KREBS CYCLE 1 6-carbon molecule 4-carbon molecule (Starting material) CoA- (Acetyl-CoA) CoA The Krebs cycle begins when a two-carbon fragment is transferred from acetyl-CoA to a four-carbon molecule (the starting material). Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

49. The Krebs Cycle: Step 2 Citric acid releases a CO 2 molecule & a H+ atom to form a 5-C compound By losing the H-atom with its electrons, the citric acid is oxidized The electron in the H-atom is transferred to NAD+ reducing it to NADH

50. The Krebs Cycle: Step 3 The 5-C compound formed in step 2 also releases a CO 2 & a H+ making a 4-C compound Again, NAD+ is reduced to NADH Note: a molecule of ATP is also synthesized from ADP

51. OVERVIEW OF THE KREBS CYCLE 2 5-carbon molecule 4-carbon molecule NADH CO 2 NADH CO 2 ATP 6-carbon molecule Then, the resulting six-carbon molecule is oxidized (a hydrogen removed to form NADH) and decarboxylated (a carbon removed to form CO2). Next, the five-carbon molecule is oxidized and decarboxylated again, and a coupled reaction generates ATP. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

52. The Krebs Cycle: Step 4 The 4-C compound made in step 3 releases a H+ to form another 4-C compound This time the H-atom is used to reduce FAD to FADH 2. FAD or flavin adenine dinucleotide is a molecule similar to NAD+; accepting electrons during redox reactions

53. The Krebs Cycle: Step 5 The 4-C compound formed in step 4 releases a H+ to regenerate oxaloacetic acid which keeps the Krebs cycle operating. The electron in the H+ reduces NAD+ to NADH Makes 2 turns

54. OVERVIEW OF THE KREBS CYCLE 3 NADH FADH 2 4-carbon molecule (Starting material) Finally, the resulting four-carbon molecule is further oxidized (hydrogens removed to form FADH2 and NADH). This regenerates the four-carbon starting material, completing the cycle. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

55. Krebs Cycle Video http://www.youtube.com/watch?v =lvoZ21P4JK8&feature=related

56. Think about this … In glycolysis … 1 glucose makes 2 pyruvic molecules … which then makes 2 molecules of acetyl CoA This 1 glucose molecule is broken down into 2 turns of the Krebs cycle These 2 turns make 4CO 2, 2-ATP, & a H+ atom … that are used to make 6- NADH & 2 FADH 2

57. Then … The CO 2 diffuses out of the cell and is given off as waste ATP can be used for energy Each glucose molecule yields only 2 molecules of ATP through the Krebs cycle … the same number as in glycolysis

59. Electron Transport Chain Linked with chemiosmosis, starts the 2 nd stage of aerobic respiration The electrons in the H-atoms from NADH & FADH 2 are at a high energy level In the ETC these molecules are passed along a series of molecules embedded in the inner mitochondrial membrane

60. Eukaryotes vs Prokaryotes of the ETC In Eukaryotes, ETC & ATP synthesis are found in the inner membrane of the mitochondria in the folds of the cristae In Prokaryotes ETC is found in the cell membrane

61. ETC step 1 NADH & FADH 2 give up electrons to the ETC NADH donates electrons at the beginning and FADH 2 donates them farther down the chain These molecule also give up protons (Hydrogen ions +)

63. ETC step 2 The electrons are passed down the chain As they move from molecule to molecule, they lose energy

65. ETC step 3 The energy lost from the electrons is used to pump protons from the matrix, building a high concentration of protons between the inner and outer membranes So, a concentration gradient of protons is created across the inner membrane An electrical gradient is also created, as the protons carry a positive charge

67. ETC step 4 The concentration and electrical gradient of protons drives the synthesis of ATP by Chemiosmosis (same process that generates ATP in photosynthesis) ATP synthase molecules are embedded in the inner membrane near the ETC molecule As protons move through ATP synthase & down their concentration and electrical gradients, ATP is made from ADP + P

69. ETC step 5 Oxygen is the final acceptor of electrons that have passed down the chain. Oxygen also accepts protons that were part of the H-atom supplied by NADH and FADH2 The protons, electrons, and oxygen all combine to form water

70. Electron Transport Chain Animation http://www.science.smith.edu/depart ments/Biology/Bio231/etc.html

71. What's the point of the ETC? The ETC helps turn NADH and FADH2 into ATP Total ATP made in glycolysis … 2 Total ATP made in Krebs … 2 Total NADH made … 10. This will be used in ETC- 1 NADH makes 3 ATP Total FADH2 made..2. This will be used in ETC – 1 FAHD2 makes 2 ATP

73. 2 2 6 ATP Pyruvate Glucose Acetyl-CoA NADH 2 6 ATP NADH 2 ATP 2 6 18ATPNADH 2 4ATP Total net ATP yield = 38ATP FADH2 Krebs cycle ATPGlycolysis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

74. Electron Transport Chain http://www.youtube.com/watch?v =Idy2XAlZIVA&feature=related

75. Fig. 9.3 (TEArt) H+H+ ATP ADP + P i Catalytic head Intermembrane space Mitochondrial matrix Rod Rotor H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.