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Respiration Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules. As this happens cells release.

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Presentation on theme: "Respiration Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules. As this happens cells release."— Presentation transcript:

1 Respiration Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules. As this happens cells release CO 2 and use up O 2 Respiration can be AEROBIC or ANAEROBIC

2 Breathing supplies oxygen to our cells and removes carbon dioxide –Breathing provides for the exchange of O 2 and CO 2 Between an organism and its environment CO 2 O2O2 O2O2 Bloodstream Muscle cells carrying out Cellular Respiration Breathing Glucose  O 2 CO 2  H 2 O  ATP Lungs Figure 6.2

3 . The human body uses energy from ATP for all its activities. –ATP powers almost all cellular and body activities

4 CELLULAR RESPIRATION Cellular respiration is an energy- releasing process. It produces ATP ATP is the universal energy source Making ATP Plants make ATP during photosynthesis Cells of all organisms make ATP by breaking down carbohydrates, fats, and protein

5 –The energy in an ATP molecule Lies in the bonds between its phosphate groups Phosphate groups ATP Energy PPP P PP Hydrolysis Adenine Ribose H2OH2O Adenosine diphosphate Adenosine Triphosphate + + ADP Figure 5.4A

6 REDOX REACTIONS –The loss of electrons is called oxidation. –The addition of electrons is called reduction

7 Overview of Aerobic Respiration C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O +ATP glucose oxygen carbon water dioxide

8 –When glucose is converted to carbon dioxide It loses hydrogen atoms, which are added to oxygen, producing water C 6 H 12 O 6 6 O 2 6 CO 2 6 H 2 O Loss of hydrogen atoms (oxidation) Gain of hydrogen atoms (reduction) Energy (ATP)Glucose + ++ Figure 6.5A

9 STAGES OF CELLULAR RESPIRATION Overview: Cellular respiration occurs in three main stages 1.Glycolysis 2.Krebs Cycle or Citric Acid Cycle 3.Electron Transport Chain or Phosphorylation

10 –Stage 1: Glycolysis –No oxygen needed. It is universal Occurs in the cytoplasm Breaks down glucose into pyruvate, producing a small amount of ATP (2)

11 GLYCOLYSIS Where?: In the cytosol of all cells. Both aerobic and anaerobic respiration begin with glycolysis. What happens?: The cell harvests energy by oxidizing glucose to pyruvate. One molecule of glucose (6 carbons) is converted to two pyruvate molecules (3 carbons) through a series of 10 reactions mediated by enzymes. Result: 2 pyruvate molecules (each with a 3 carbon backbone) 2 NADH molecules. Carrier that picks up hydrogens stripped from glucose. 2 ATP molecules. 4 are made but cells use 2 to start glycolysis so net gain is 2

12 An overview of cellular respiration

13 Preparatory steps to enter the Krebs cycle The 2 pyruvate molecules enter the mitochondrion and an enzyme strips one carbon from each pyruvate. This two carbon molecule is picked up by Co- enzyme A in preparation for the Krebs cycle. This is acetyl CoA. This is what enters the Krebs cycle: C-C-CoA (oxaloacetate)

14 Stage 2 : The citric acid cycle or Krebs cycle Takes place in the mitochondria Completes the breakdown of glucose ( catabolism), producing a small amount of ATP ( 2ATP ) Pyruvate is broken down to carbon dioxide More coenzymes are reduced. Supplies the third stage of cellular respiration with electrons (hydrogen carriers such as NADH)

15 KREBS CYCLE or citric acid cycle This cycle involves a series of 8 steps forming and rearranging. Each time it releases CO2 and NADH carries hydrogen to the last step. 6 CO 2 are given off as waste (this is the most oxidized form of Carbon) In total: 6 CO 2 6 NADH are produced and 2 FADH and only 2 ATP

16 An overview of cellular respiration

17 Stage 3: Oxidative phosphorylation or electron transport chain Occurs in the mitochondria (inner membrane) Uses the energy released by “falling” electrons to pump H + across a membrane Harnesses the energy of the H + gradient through chemiosmosis, producing ATP

18 Chemiosmosis Chemiosmosis is an energy coupling mechanism that uses energy stored on H+ Chemiosmosis is the coupling of the REDUX reactions of the electron transport chain to ATP synthesis

19 –NADH passes electrons to an electron transport chain –As electrons “fall” from carrier to carrier and finally to O 2 Energy is released in small quantities H2OH2O NAD  NADH ATP HH HH Controlled release of energy for synthesis of ATP Electron transport chain 2 O2O2 2e   1 2 Figure 6.5C

20 ELECTRON TRANSPORT CHAIN Electron transport systems are embedded (protein molecules) in inner mitochondrial membranes ( cristae) NADH and FADH 2 give up electrons that they picked up in earlier stages to electron transport system Electrons are transported through the system The final electron acceptor is oxygen. The hydrogen combines with the oxygen to form water

21 Electron transport chain Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron flow Electron carrier NADH NAD + FADH 2 FAD H2OH2O ATP ADP ATP synthase H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+  P O2O2 Electron Transport Chain Chemiosmosis. OXIDATIVE PHOSPHORYLATION Figure 6.10

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23 HOW MUCH TOTAL ATP (ENERGY) WAS PRODUCED? Glycolysis 2 ATP formed by substrate-level phosphorylation Krebs cycle and preparatory reactions 2 ATP formed by substrate-level phosphorylation Electron transport phosphorylation ATP formed =38 Most ATP production occurs by oxidative phosphorylation or electron transport chain

24 WHY OXYGEN? Electron transport phosphorylation requires the presence of oxygen Oxygen withdraws spent electrons from the electron transport system, then combines with H + to form water

25 Web site tutorials to check: on/respiration.htmlhttp://www.sp.uconn.edu/~terry/Comm on/respiration.html port_system.htmhttp://www2.nl.edu/jste/electron_trans port_system.htm online.com/objects/MBY2604/MBY2604.s wfhttp://www.wisc- online.com/objects/MBY2604/MBY2604.s wf

26 An overview of cellular respiration

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29 Animation: Cell Respiration Overview Animation: Cell Respiration Overview

30 How efficient is cellular respiration? Only about 40% efficient. In other words, a call can harvest about 40% of the energy stored in glucose. Most energy is released as heat

31 Evolution of cellular respiration When life originated, atmosphere had little oxygen Earliest organisms used anaerobic pathways Later, photosynthesis increased atmospheric oxygen Cells arose that used oxygen as final acceptor in electron transport ( without oxygen to act as the final hydrogen acceptor the cells will die)

32 Fermentation Fermentation allows some cells to produce ATP without oxygen. This is Anaerobic respiration

33 ANAEROBIC RESPIRATION Fermentation is an anaerobic alternative to cellular respiration Do not use oxygen Produce less ATP( 2) than aerobic pathways Two types. One produces alcohol and the other lactic acid as waste products –Fermentation pathways –Anaerobic electron transport

34 Fermentation –Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP Begin with glycolysis Do not break glucose down completely to carbon dioxide and water Yield only the 2 ATP from glycolysis Steps that follow glycolysis serve only to regenerate NAD +

35 Yeast Single-celled fungi Carry out alcoholic fermentation Saccharomyces cerevisiae –Baker’s yeast –Carbon dioxide makes bread dough rise Saccharomyces ellipsoideus –Used to make beer and wine

36 Our muscle cells… In the absence of oxygen our muscles can carry out fermentation, but the pyruvate from glycolysis is turned into lactic acid instead of alcohol

37 –In alcohol fermentation NADH is oxidized to NAD + while converting pyruvate to CO 2 and ethanol NAD  NADH NAD  GLYCOLYSIS 2 ADP  2 P ATP Glucose 2 Pyruvate released CO 2 2 Ethanol 2 2 Figure 6.13B Figure 6.13C

38 More details…

39 Two stages of glycolysis Energy-requiring steps –ATP energy activates glucose and its six-carbon derivatives Energy-releasing steps –The products of the first part are split into three-carbon pyruvate molecules –ATP and NADH form

40 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate –In glycolysis, ATP is used to prime a glucose molecule Which is split into two molecules of pyruvate NAD  NADH HH Glucose 2 Pyruvate ATP 2 P 2 ADP Figure 6.7A

41 –In the first phase of glycolysis ATP is used to energize a glucose molecule, which is then split in two ATP Glucose PREPARATORY PHASE (energy investment) ADP Step Glucose-6-phosphate Fructose-6-phosphate P P Fructose-1,6-diphosphate ATP ADP P P Steps – A fuel molecule is energized, using ATP. Step A six-carbon intermediate splits into two three-carbon intermediates Figure 6.7C

42 Pyruvate ATP ADP ATP ADP P ATP ADP P 2-Phosphoglycerate P H2OH2O H2OH2O Phosphoenolpyruvate (PEP) Steps – ATP and pyruvate are produced. P 3 -Phosphoglycerate P P Step A redox reaction generates NADH. P NADH P P P PP P +H  ENERGY PAYOFF PHASE Glyceraldehyde-3-phosphate (G3P) 1,3 -Diphosphoglycerate P NAD   –In the second phase of glycolysis ATP, NADH, and pyruvate are formed

43 Net Energy Yield from Glycolysis Energy requiring steps: 2 ATP invested Energy releasing steps: 2 NADH formed 4 ATP formed Glycolysis net yield is 2 ATP and 2 NADH

44 Preparatory reactions before the Krebs cycle Preparatory reactions –Pyruvate is oxidized into two-carbon acetyl units and carbon dioxide –NAD + is reduced pyruvate + coenzyme A + NAD + acetyl-CoA + NADH + CO 2 One of the carbons from pyruvate is released in CO 2 Two carbons are attached to coenzyme A and continue on to the Krebs cycle

45 CO 2 Pyruvate NAD  NADH  H  CoA Acetyl CoA (acetyl coenzyme A) Coenzyme A Figure 6.8 Pyruvate is gets ready for the citric acid cycle –Prior to the citric acid cycle Enzymes process pyruvate, releasing CO 2 and producing NADH and acetyl CoA 1 2 3

46 Krebs cycle –The acetyl units are oxidized to carbon dioxide –NAD + and FAD are reduced Products: Coenzyme A 2 CO 2 3 NADH FADH 2 ATP

47 The citric acid cycle (Krebs)completes the oxidation of organic fuel (glucose), generating many NADH and FADH 2 molecules –In the citric acid cycle The two-carbon acetyl part of acetyl CoA is oxidized CoA CO 2 NAD  NADH FAD FADH 2 ATPP CITRIC ACID CYCLE ADP  3 3  3 H  Acetyl CoA 2 Figure 6.9A

48 Krebs Cycle or Citric Acid Cycle

49 For each turn of the Krebs cycle Two CO2 molecules are released ( All of the carbon molecules in pyruvate end up in carbon dioxide ) Three NADH and one FADH 2 (Coenzymes are reduced, they pick up electrons and hydrogen) One molecule of ATP is formed for each turn so the net yield of ATP for the Krebs or Citric Acid cycle is 2 ATP molecules.

50 What happened to co-enzymes (NAD and FAD) during the first two stages? Co-enzymes were reduced (gained electrons) Glycolysis2 NADH Preparatory reactions 2 NADH Krebs cycle 2 FADH NADH Total 2 FADH NADH

51 Most ATP production occurs by oxidative phosphorylation or electron transport chain –Electrons from NADH and FADH 2 Travel down the electron transport chain to oxygen, which picks up H + to form water –Energy released by the redox reactions Is used to pump H + into the space between the mitochondrial membranes

52 ELECTRON TRANSPORT CHAIN OR PHOSPHORYLATION Takes place in the mitochondria Coenzymes deliver electrons to electron transport systems Electron transport sets up H + ion gradients Flow of H + down gradients powers ATP formation The net yield from oxidative phosphorilation is 32 to 34 ATP molecules

53 Making ATP : Chemiosmotic model

54 –In chemiosmosis, the H + diffuses back through the inner membrane through ATP synthase complexes Driving the synthesis of ATP Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron flow Electron carrier NADH NAD + FADH 2 FAD H2OH2O ATP ADP ATP synthase H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+  P O2O2 Electron Transport Chain Chemiosmosis. OXIDATIVE PHOSPHORYLATION Figure 6.10

55 Certain poisons interrupt critical events in cellular respiration –Various poisons Block the movement of electrons Block the flow of H + through ATP synthase Allow H + to leak through the membrane H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ O2O2 H2OH2O P ATP NADHNAD + FADH 2 FAD Rotenone Cyanide, carbon monoxide Oligomycin DNP ATP Synthase  2 ADP  Electron Transport Chain Chemiosmosis 1 2 Figure 6.11

56 Review: Each molecule of glucose yields many molecules of ATP –Oxidative phosphorylation, using electron transport and chemiosmosis Produces up to 38 ATP molecules for each glucose molecule that enters cellular respiration NADH FADH 2 Cytoplasm Electron shuttle across membrane Mitochondrion GLYCOLYSIS Glucose Pyruvate by substrate-level phosphorylation by oxidative phosphorylation OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) 2 Acetyl CoA CITRIC ACID CYCLE  2 ATP  about 34 ATP Maximum per glucose: About 38 ATP (or 2 FADH 2 ) Figure 6.12

57 Anaerobic Electron Transport Carried out by certain bacteria Electron transport system is in bacterial plasma membrane Final electron acceptor is compound from environment (such as nitrate), NOT oxygen ATP yield is almost as good as from aerobic respiration

58 INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS Cells use many kinds of organic molecules as fuel for cellular respiration

59 –Carbohydrates, fats, and proteins can all fuel cellular respiration When they are converted to molecules that enter glycolysis or the citric acid cycle OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Food, such as peanuts CarbohydratesFatsProteins Sugars Glycerol Fatty acids Amino acids Amino groups GlucoseG3P Pyruvate Acetyl CoA CITRIC ACID CYCLE ATP GLYCOLYSIS Figure 6.14

60 How is energy obtained from proteins? Proteins are broken down to amino acids Amino acids are broken apart Amino group is removed, ammonia forms, is converted to urea and excreted Carbon backbones can enter the Krebs cycle

61 How do we get energy from fats? Most stored fats are triglycerides Triglycerides are broken down to glycerol and fatty acids Glycerol is converted to PGAL, an intermediate of glycolysis Fatty acids are broken down and converted to acetyl-CoA, which enters Krebs cycle

62 LE 9-19 Citric acid cycle Oxidative phosphorylation Proteins NH 3 Amino acids Sugars Carbohydrates Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA Fatty acids Glycerol Fats

63 Food molecules provide raw materials for biosynthesis –Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials –This process of biosynthesis Consumes ATP ATP needed to drive biosynthesis ATP CITRIC ACID CYCLE GLUCOSE SYNTHESIS Acetyl CoA PyruvateG3P Glucose Amino groups Amino acids Fatty acids Glycerol Sugars Carbohydrates FatsProteins Cells, tissues, organisms Figure 6.15

64 The fuel for respiration ultimately comes from photosynthesis –All organisms Can harvest energy from organic molecules –Plants, but not animals Can also make these molecules from inorganic sources by the process of photosynthesis Figure 6.16

65 Electrons “fall” from organic molecules to oxygen during cellular respiration In cellular respiration, glucose and other fuels are oxidized, releasing energy. In the summary equation of cellular respiration: C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O+ ATP Glucose is oxidized (loses electrons), oxygen is reduced ( gains electrons) Cellular respiration does not oxidize glucose in a single step that transfers all the hydrogen in the fuel to oxygen at one time. glucose is broken down gradually in a series of steps, each catalyzed by a specific enzyme


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