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Cellular Respiration Topic 3.7 and 3.8. Assessment Statements: Core 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the.

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Presentation on theme: "Cellular Respiration Topic 3.7 and 3.8. Assessment Statements: Core 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the."— Presentation transcript:

1 Cellular Respiration Topic 3.7 and 3.8

2 Assessment Statements: Core 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.

3 Assessment Statements: Higher Level

4 Energy metabolism and REDOX reactions Metabolism is the sum of all of the chemical reactions in an organism: catabolic (breakdown) and anabolic (synthetic) Respiration is a catabolic pathway Photosynthesis is an anabolic pathway The two processes are closely linked in plants REDOX (oxidation- reduction) reactions play a key role in energy flow through organisms This is because the electrons flowing from one molecule to another are carrying energy with them

5 REDOX reactions OXIDATIONREDUCTION Loss of electronsGain of electrons Gain of oxygenLoss of oxygen Loss of hydrogenGain of hydrogen Results in C-O bondsResults in C-H bonds Results in a compound with lower potential energy Results in a compound with higher potential energy OIL RIG LEO says GER

6 Definition of cellular respiration Controlled release of energy from organic compounds to produce ATP Cells break down organic compounds by SLOW oxidation Chemical energy is stored in covalent bonds By releasing energy in a controlled way, it can be trapped in the ‘useful’ form of ATP

7 REDOX reactions in respiration Cells tap energy from electrons transferred from organic fuels to oxygen Glucose gives up energy as it is oxidized: it transfers its electrons (and energy) to water The protons follow the electrons to produce water Loss of hydrogen atoms Energy Gain of hydrogen atoms

8 Where Does Cellular Respiration Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Takeplace in the mitochondria Krebs Cycle & ETC Take place in the mitochondria

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10 Cellular Respiration: Standard level How does the process of cellular respiration yield ATP (chemical energy) from food? 1.What do you already know about cellular respiration? 2.What organelle in the cell is the “powerhouse” that makes energy for the cell ?

11 What is ATP? Energy ‘currency’ used by all cells Adenosine triphosphate Organic molecule containing high-energy phosphate bonds

12 Chemical Structure of ATP 3 Phosphates Ribose Sugar Adenine Base

13 How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP ATP hydrolase (ATP’ase) catalyses the breakdown of ATP into ADP + P i

14 Each day, you hydrolyse 10 25 ATP molecules ATP-ase ATP Synthetase

15 H2OH2O HYDROLYSIS (Adding H 2 O)

16 How is ATP re-made? Substrate-level phosphorylation (using enzymes: in the cytoplasm of the cell and the matrix of the mitochondrion) Chemiosmosis (in the mitochondria, using ATP synthase)

17 Substrate level phosphorylation and chemiosmosis GLYCOLYSIS GlucosePyruvic acid KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Substrate Level Phos.Substrate Level Phos.Oxidative Phos.

18 REDOX reactions in respiration Cells tap energy from electrons transferred from organic fuels to oxygen Glucose gives up energy as it is oxidized: it transfers its electrons (and energy) to water The protons follow the electrons to produce water Loss of hydrogen atoms Energy Gain of hydrogen atoms

19 Enzymes remove electrons from glucose molecules and transfer them to a coenzyme Hydrogen carriers such as NAD + shuttle electrons in redox reactions OXIDATION Dehydrogenase and NAD + REDUCTION

20 NADH delivers electrons to a series of electron carriers in an electron transport chain As electrons move from carrier to carrier, their energy is released in small quantities Redox reactions release energy when electrons “ fall ” from a hydrogen carrier to oxygen Energy released and now available for making ATP ELECTRON CARRIERS of the electron transport chain Electron flow

21 Two mechanisms generate ATP ATP can be made by transferring phosphate groups from organic molecules to ADP This process is called substrate-level phosphorylation Occurs in cytoplasm and in matrix of the mitochondrion

22 1. Cells use the energy released by “ falling ” electrons to pump H + ions across a membrane The energy of the gradient is harnessed to make ATP by the process of chemiosmosis also known as oxidative phosphorylation Two mechanisms generate ATP Figure 6.7A High H+ concentration ATP synthase uses gradient energy to make ATP Membrane Energy from Low H+ concentration ATP synthase Electron transport chain

23 Definition of cellular respiration Controlled release of energy from organic compounds to produce ATP Cells break down organic compounds by SLOW oxidation Chemical energy is stored in covalent bonds By releasing energy in a controlled way, it can be trapped in the ‘useful’ form of ATP

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26 Cellular Respiration Breakdown of one glucose results in 36 to 38 ATP molecules Metabolic Pathway that breaks down carbohydrates Metabolic Pathway that breaks down carbohydrates Process is exergonic as high-energy glucose is broken into CO 2 and H 2 O Process is exergonic as high-energy glucose is broken into CO 2 and H 2 O Process is also catabolic because glucose breaks into smaller molecules Process is also catabolic because glucose breaks into smaller molecules

27 Equations for aerobic respiration All of these are fine!....

28 Equation for Cellular Respiration 6CO 2 + 6H 2 0 + e - + 36-38 ATP + heat C 6 H 12 O 6 + 6O 2 YIELDS

29 Stages of Cellular Respiration 1.Glycolysis ALWAYS OCCURS 2.Anaerobic pathways if no oxygen available (Lactic acid and Ethanol fermentation) 3.Aerobic pathways if oxygen available (Link reaction, Krebs cycle, electron transport chain)

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31 Where Does Cellular Respiration Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Takeplace in the mitochondria Krebs Cycle & ETC Take place in the mitochondria

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33 Glycolysis: Always the initial stage of respiration Location: cytoplasm Substrate: glucose Requires input of 2 ATP Products: pyruvate, (NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required the movie...

34 Glycolysis

35 Summary of glycolysis 1.Occurs in the cytoplasm of the cell 2.Two ATP molecules are used to start the process (‘energy investment phase’) 3.A total of 4 ATP’s are produced (net gain of 2 ATP) 4.2 molecules of NADH are produced 5.Involves substrate level phosphorylation, lysis, oxidation and ATP formation 6.Controlled by enzymes: when ATP levels in the cell are high, feedback inhibition will block the first enzyme in the pathway 7.Produces 2 pyruvate molecules at the end

36 If no oxygen is available, glycolysis (anaerobic) is followed by fermentation (anaerobic)

37 Why fermentation? In the absence of oxygen, glycolysis soon stops unless there is an alternative acceptor for the electrons produced from the glycolytic pathway

38 Fermentation 1. Alcoholic fermentation Pyruvate is converted into ethanol plus carbon dioxide and NAD + 2.Lactate fermentation Pyruvate is converted into lactate and NAD +

39 Alcoholic fermentation in yeast

40 Pyruvate is produced from glycolysis 3-carbon pyruvate is converted to 2-carbon ethanol and carbon dioxide Generation of carbon dioxide helps bread products to rise Yeast is used to produce ethanol

41 Lactate fermentation in mammals Lactate is a 3- carbon molecule NAD + is regenerated to allow glycolysis to continue

42 Aerobic respiration: Higher level 8.1.4: Explain aerobic respiration: the Link reaction, the Krebs cycle, the role of NADH and H +, the electron transport chain and the role of oxygen 8.1.5: Explain oxidative phosphorylation in terms of chemiosmosis

43 Aerobic respiration Takes place in the mitochondria of eukaryotic cells Substrate: pyruvate Produces LOTS of ATP (28 – 38 ATP): 90% of total ATP from respiration Also produces carbon dioxide, water and heat Oxygen is the final electron acceptor

44 Aerobic respiration 2 pyruvate molecules enter the mitochondrion Pyruvate loses a CO 2 molecule and becomes acetyl CoA Krebs cycle produces 2 ATP, 4 CO 2, 6 NADH and 3 FADH 2 Electron transport chain produces 34 ATP and water Aerobic respiration completely oxidises glucose Anaerobic respiration does not completely oxidise glucose – ethanol, lactate and carbon dioxide are by-products

45 Get to know your mitochondrial structure!

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47 Stages of aerobic respiration 1.The ‘link’ reaction 2.The Krebs cycle 3.The electron transport chain 4.Chemiosmosis and oxidative phosphorylation

48 The Link Reaction Steps 2 in aerobic respiration (step 1 is glycolysis in the cytoplasm) After glycolysis, when there is ample oxygen… 2 pyruvate molecules from glycolysis move into the matrix of the mitochondrion for the Link reaction and the Krebs cycle

49 Matrix – Link Reaction Krebs Cycle 2 2

50 The Link reaction The link reaction converts pyruvate (3C) into acetyl Coenzyme A (2C), producing carbon dioxide and NADH in the process

51 Krebs: The walk-through... Krebs: the movie… The 2C acetyl Coenzyme A enters the Krebs cycle It joins oxaloacetate (4C) to form citrate (6C). Two carbon atoms are then lost as carbon dioxide and the cycle repeats. Hydrogen is released during this cycle to reduce the coenzymes NAD + and FAD to 3 NADH and 1 FADH 2 for each cycle ATP is also released The Krebs Cycle (Citric Acid/TCA cycle)

52 Each molecule of glucose produces 2 pyruvates in glycolysis Leading to 2 acetyl CoA molecules in the link reaction Krebs cycle turns TWICE for each molecule of glucose

53 Fill in your table! SubstanceOxidised/Reduced/NeitherReason NAD + NADH FADH 2 FAD

54 How did you do? SubstanceOxidised/Reduced /Neither Reason NAD + NADH FADH 2 FAD oxidised reduced neither +ve due to lost electron gained H from organic molecule no loss/gain of H/electrons

55 Glycolysis: 2 ATP, 2 NADH, 2 pyruvate Link: 2 NADH, CO 2 Krebs :2 ATP, 6 NADH, 2 FADH 2, 2 CO 2 Overall:4 ATP, 10 NADH, 2 FADH 2 Production PER glucose molecule

56 and finally…. The electron transport chain, chemiosmosis and oxidative phosphorylation

57 The movie…

58 Chemiosmosis in the mitochondrion Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron carrier Electron flow ELECTRON TRANSPORT CHAIN ATP SYNTHASE

59 Rotenone Cyanide, carbon monoxide Oligomycin ELECTRON TRANSPORT CHAIN ATP SYNTHASE Poisons interrupt critical events in cellular respiration

60 The electrons from NADH and FADH 2 travel down the electron transport chain to oxygen Energy released by the electrons is used to pump H + (protons) into the space between the mitochondrial membranes In chemiosmosis, the H + ions diffuse back through the inner membrane through ATP synthase, which capture the energy to make ATP Chemiosmosis powers most ATP production

61 Questions… What is the role and the position of oxygen in the electron transport chain? What is the benefit of having cristae in the mitochondria?

62 Chemiosmosis/ ETC occurs on the inner membrane of the mitochondria Figure 6.12 Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron carrier Electron flow ELECTRON TRANSPORT CHAIN ATP SYNTHASE

63 Final checks and balances ProcessATP usedATP producedNet ATP gain Glycolysis Krebs cycle Electron Transport Chain/ Chemiosmosis Total

64 Final checks and balances ProcessATP usedATP producedNet ATP gain Glycolysis242 Krebs cycle022 Electron Transport Chain/ Chemiosmosis 032 Total23836

65 Review of mitochondrial structure and function Outer mitochondrial membrane Matrix Cristae Inner mitochondrial membrane Space between inner and outer membranes

66 Review of mitochondrial structure and function Outer mitochondrial membraneSeparates contents of mitochondrion from rest of cell MatrixLike cytoplasm: enzymes for the Link reaction and the Krebs cycle CristaeIncreases surface area for oxidative photophosphorylation Inner mitochondrial membraneCarriers for electron transport chain and ATP synthase and Space between inner and outer membranes Reservoir for protons (H + ions) to create concentration gradient

67 For each glucose molecule that enters cellular respiration, respiration produces up to 38 ATP molecules KREBS CYCLE Electron shuttle across membranes Cytoplasmic fluid GLYCOLYSIS Glucose 2 Pyruvic acid 2 Acetyl CoA KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Mitochondrion by substrate-level phosphorylation used for shuttling electrons from NADH made in glycolysis by substrate-level phosphorylation by chemiosmotic phosphorylation Maximum per glucose:

68 Some practice questions on respiration… 1.How do cells capture the energy released by cell respiration? A.They store it in molecules of carbon dioxide. B.They produce glucose. C.The energy is released as pyruvate. D.They produce ATP. (Total 1 mark)

69 Some practice questions on respiration… 2.Which process produces the most ATP per molecule of glucose? A.Anaerobic respiration in a yeast cell B.Aerobic respiration in a bacterial cell C.Glycolysis in a human liver cell D.The formation of lactic acid in a human muscle cell (Total 1 mark)

70 Some practice questions on respiration… 3. Which of the following is the best definition of cell respiration? A.A process needed to use energy, in the form of ATP, to produce organic compounds B.A process used to provide oxygen to the atmosphere C.A controlled release of energy, in the form of ATP, from organic compounds in cells D.A controlled release of energy in the production of food from organic compounds (Total 1 mark)

71 Some practice questions on respiration… 4. Which of the following processes produces CO 2 ? I.Glycolysis II.Alcohol (ethanol) fermentation III.Lactic acid production A.I only B.II only C.I and II only D.I, II and III (Total 1 mark)

72 Some practice questions on respiration… 4. Which of the following processes produces CO 2 ? I.Glycolysis II.Alcohol (ethanol) fermentation III.Lactic acid production A.I only B.II only C.I and II only D.I, II and III (Total 1 mark)

73 Some practice questions on respiration… 4. State a word equation for anaerobic cell respiration in humans. (1 mark)


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