Ch. 9 Cell Respiration. Title: Oct 15 3:24 PM (1 of 53)

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1 Ch. 9 Cell Respiration Title: Oct 15 3:24 PM (1 of 53)

2 Essential question: How do cells use stored chemical energy in organic molecules and to generate ATP? Title: Oct 15 3:28 PM (2 of 53)

3 Title: Oct 19 9:29 AM (3 of 53)

4 Title: Oct 19 9:31 AM (4 of 53) Review of how ATP drives cellular work

5 Where do organic compounds store their energy? in their arrangement of atoms (potential energy) by using enzymes, breakdown molecules to do work and produce heat (catabolic pathways) two methods: fermentation partial degrading of sugars without using oxygen cellular respiration degrading of sugars with the use of oxygen Title: Oct 15 3:31 PM (5 of 53)

6 Cellular respiration Overall Reaction organic + oxygen CO2 + water + energy compounds organic compounds that can be used are carbs, proteins, and fats, use glucose as example C H O + O is exergonic = G = 686kcal/mol 6CO + 6H O + energy (ATP + heat) also uses redox reactions Title: Oct 15 3:36 PM (6 of 53)

7 C H O + 6O becomes oxidized 6CO + 6H O + energy becomes reduced hydrogen is transferred from glucose to oxygen; by oxidizing glucose, respiration gives off stored energy from glucose to make ATP enzymes lower the activation energy needed to make this happen Title: Oct 15 3:52 PM (7 of 53)

8 In cellular respiration, hydrogen atoms are not transferred directly to oxygen are passed to coenzyme called NAD+ (nicotinamide adenine dinucleotide) is an electron acceptor, an oxidizing agent Title: Oct 15 6:10 PM (8 of 53)

9 dehydrogenases remove a pair of hydrogen atoms (2 e, 2p+) from sugar (oxidizing it) dehydrogenase gives 2 e and 1 p+ to NAD+, the othe p+ is released into surrounding solution becomes NADH Title: Oct 19 9:36 AM (9 of 53)

10 To finally get electrons to oxygen, need an electron transport chain (proteins imbedded in inner membrane of mitochondrion) electrons (from food) are shuttled by NADH to the top of the ETC (high energy end) At the bottom (lower energy end) oxygen captures the electrons with hydrogen protons to form water Oxygen is the final electron acceptor Title: Oct 15 6:18 PM (10 of 53)

11 Title: Oct 19 9:37 AM (11 of 53) Electron transport chains

12 Title: Oct 15 6:46 PM (12 of 53) Overview of Cellular respiration

13 Stages of Cellular respiration: Glycolysis Citric Acid cycle (Kreb's cycle) Oxidative phosphorylation: Electron transport chain and chemiosmosis Title: Oct 15 6:47 PM (13 of 53)

14 Glycolysis= "splitting of sugar" catabolic pathway occurs in cytosol glucose (6 C sugar) is split into 2 three C sugars which are then oxidized and rearranged to form 2 molecules of pyruvate consists of 10 steps (each requires an enzyme) some steps use energy (ATP) some steps form ATP net yield = 2 ATP + 2 NADH + 2 pyruvate Title: Oct 15 6:49 PM (14 of 53)

15 Title: Oct 19 9:40 AM (15 of 53) Energy input and output of glycolysis

16 no CO2 is released in glycolysis glycolysis occurs with (aerobic) or without (anaerobic) presence of oxygen Title: Oct 15 6:55 PM (16 of 53)

17 Title: Oct 19 9:43 AM (17 of 53) Glycolysis energy investment phases

18 Title: Oct 19 9:44 AM (18 of 53) Energy payoff phase of glycolysis

19 Citric Acid Cycle catabolic pathway takes place in mitochondrion matrix starts by having pyruvate transported inside mitochondrion Title: Oct 15 6:59 PM (19 of 53)

20 Step 1 pyruvate's carboxyl gp. is removed as CO2 and released by cell Title: Oct 15 7:04 PM (20 of 53)

21 Step 2 remaining 2 C fragment is oxidized to form acetate, an enzyme transfers e to NAD+ to become NADH Title: Oct 19 9:47 AM (21 of 53)

22 Step 3 coenzyme A (derived from a B vitamin) is attached t acetate (makes this gp. reactive) Acetyl CoA; acetyl gp. then goes into citric acid cycle for more oxidation Title: Oct 19 9:47 AM (22 of 53)

23 Citric acid cycle = tricarboxylicacid cycle = Kreb's Cycle pathway figured out by Hans Krebs in 1930s bio.html Title: Oct 15 7:11 PM (23 of 53)

24 2 overview: (per pyruvate actually 2 going in ) pyruvate is broken down into: 3 CO2 1 ATP formed via substrate level phosphorylation 4 NAD+ are reduced to 4 NADH 1 FAD is reduced to FADH 4 NADH and 1 FADH 2 go to ETC from here 2 *FAD = flavin adenine dinucleotide (derived from riboflavin a B vitamin) Title: Oct 15 7:12 PM (24 of 53)

25 has 8 steps, each catalyzed by an enzyme step 1 acetyl gp is added to oxaloacetate to make citrate (condensation reaction) steps 2 7 citrate is decomposed and converted back to oxaloacetate Title: Oct 15 7:18 PM (25 of 53)

26 Title: Oct 15 7:27 PM (26 of 53) Citric acid cycle

27 Title: Oct 19 9:53 AM (27 of 53) Summary of Kreb's Cycle

28 What happens to the electrons being carried by NADH and FADH 2? Oxidative phosphorylation The production of ATP generated by redox reactions in the Electron Transport Chain Title: Oct 15 7:28 PM (28 of 53)

29 Electron Transport Chain in inner membrane of mitochondrion has increased surface area (cristae) for lots of ETCs mostly made of proteins multiprotein complexes #I IV prosthetic gps. are attached to these proteins nonprotein needed for catalysis by enzymes during chain electron carriers alternate between reduced and oxidized states as they gain and lose electrons Title: Oct 15 7:33 PM (29 of 53)

30 Title: Oct 15 7:37 PM (30 of 53) Free energy change during electron transport

31 In ETC: NADH flavoprotein passes electrons iron sulfur protein ubiquinone (not a protein) series of cytochromes cytochrome a3 oxygen (final electron acceptor) Title: Oct 15 7:38 PM (31 of 53)

32 cytochromes have an iron group that accepts and donates electrons, each has a different heme grp. oxygen then picks up two hydrogens from solution to form water FADH 2adds electrons to the ETC at complex II (a lower energy level than NADH) makes 1/3 less energy for ATP synthesis than NADH *ETC makes no ATP its purpose is to ease the fall of electrons to release energy in small amounts at a time or otherwise would be explosive Title: Oct 15 7:47 PM (32 of 53)

33 Chemiosmosis =an energy coupling mechanism that uses stored energy in the form of a hydrogen ion gradient across a membrane to drive cellular work in inner mitochondrion membrane ATP synthase is a enzyme used to make ATP from ADP and inorganic phosphate ATP synthase uses a concentration gradient of hydrogen ions to power ATP synthesis Title: Oct 15 7:53 PM (33 of 53)

34 chemiosmosis couples electron transport chain to ATP synthesis Title: Oct 19 9:59 AM (34 of 53)

35 ATP synthase four parts made of polypeptides a. rotor within membrane spins when hydrogen ions flow past it down gradient b. stator anchored in membrane, holds knob stationary c. rod extends into knob and spins, causing a conformational change and activating catalytic sites in the knob d. knob stationary, has three catalytic sites that join inorganic phosphate to ADP to make ATP Title: Oct 15 7:58 PM (35 of 53)

36 Title: Oct 19 9:58 AM (36 of 53) ATP synthase

37 How does the hydrogen ion gradient get produced? from electron transport chain certain steps in ETC cause H+ to be taken up and released into the surrounding solution H+ is accepted from mitochondrial matrix and deposited in intermembrane space H+ gradient = proton motive force Title: Oct 15 8:03 PM (37 of 53)

38 ATP yield per molecule of glucose at each stage in cellular respiration Title: Oct 15 8:16 PM (38 of 53)

39 each NADH generates 3 ATP each FADH generates 2 ATP 2 net result = 36 or 38 ATP per molecule of glucose (depends on variables) 40% of energy in glucose is transferred to ATP, the rest is lost as heat Title: Oct 15 8:18 PM (39 of 53)

40 How can a cell make ATP if there is no oxygen present? Fermentation Title: Oct 15 10:02 PM (40 of 53)

41 Fermentation generates ATP by substrate level phosphorylation as long as there is enough NAD+ (get enough because in anaerobic conditions,electrons are transferred from NADH to pyruvate) pyruvate is electron acceptor for oxidizing NADH back to NAD+ and can then be reused in glycolysis Title: Oct 15 10:08 PM (41 of 53)

42 two types of fermentation: 1.alcohol fermentation (yeast & bacteria) 2. lactic acid fermentation (yeast/ fungi used in dairy industry, and human muscle cells) Title: Oct 15 10:18 PM (42 of 53)

43 Alcohol fermentation end product = ethanol makes 2 ATP, 2 carbon dioxide Title: Oct 15 10:13 PM (43 of 53)

44 Lactic Acid Fermentation end product is lactate (ion form of lactic acid) 2 ATP made Title: Oct 15 10:20 PM (44 of 53)

45 So: Both fermentation and cellular respiration: use glycolysis to oxidize glucose produce 2 ATP by substrate level phosphorylation NAD+ is oxidizing agent that accepts electrons from food in glycolysis Title: Oct 15 10:22 PM (45 of 53)

46 Differences: fermentation final electron acceptor = pyruvate or acetaldehyde respiration final electron acceptor = oxygen respiration has citric acid cycle respiration can make more ATP per sugar molecule facultative anaerobes are yeasts or bacteria that can make enough ATP to survive using either fermentation or respiration our muscle cells are like facultative anaerobes Title: Oct 15 10:27 PM (46 of 53)

47 glycolysis is important in evolution before oxygen was present in the atmosphere organisms could use glycolysis to make ATP is the most widespread metabolic pathway because happens in cytosol is also evidence it evolved early Title: Oct 15 10:32 PM (47 of 53)

48 Types of molecules that can be used for glycolysis: 1. carbohydrates: if dissaccharides, polysaccharides, first need to be hydrolyzed to glucose and other monosaccharides 2. proteins: must be hydrolyzed to amino acids, then converted by enzymes to intermediates in glycolysis and citric acid cycle (amino gps must be removed first=deamination) 3. Fats:digested to glycerol and fatty acids, glycerol is converted to glyceraldehyde 3 phosphate (intermediate in glycolysis) fatty acids undergo beta oxidation to get 2 C fragments that can enter the citric acid cycle as acetyl CoA Title: Oct 15 10:36 PM (48 of 53)

49 Title: Oct 19 10:04 AM (49 of 53) How different molecules are involved in Cellular respiration

50 Anabolic pathways that are used by organisms are related to glycolysis and citric acid cycle some intermediates of glycolysis and citric acid cycle can be used to synthesize other compounds can make amino acids using compounds from citric acid cycle glucose made from pyruvate fatty acids made from acetyl CoA Title: Oct 15 10:45 PM (50 of 53)

51 feedback inhibition regulates cellular respiration end product inhibits an enzyme that catalyzes part of the pathway ex. phosphofructokinase (allosteric enzyme with receptor sites for specific inhibitors and activators) if ATP high gets inhibited, slows glycolysis if AMP high gets stimulated if citrate is high in mitochondria, some gets in cytosol and inhibits enzyme if citrate is low, glycolysis increases Title: Oct 15 10:52 PM (51 of 53)

52 Title: Oct 19 10:05 AM (52 of 53) Control of cellular respiration

53 Title: Oct 22 11:45 AM (53 of 53)