Cellular Respira,on. Topic 3.7 and 3.8

Size: px

Start display at page:

Download "Cellular Respira,on. Topic 3.7 and 3.8"

Anabel Parrish
6 years ago
Views:

1 Cellular Respira,on Topic 3.7 and 3.8

2 Defini,on of cellular respira,on Controlled release of energy from organic compounds to produce ATP Cells break down organic compounds by SLOW oxida,on Chemical energy is stored in covalent bonds By releasing energy in a controlled way, it can be trapped in the useful form of ATP

3 Defini,on of cellular respira,on Controlled release of energy from organic compounds to produce ATP Cells break down organic compounds by SLOW oxida,on Chemical energy is stored in covalent bonds By releasing energy in a controlled way, it can be trapped in the useful form of ATP

4 Where Does Cellular Respira0on Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Take place in the mitochondria

6 The source of ATP can be carbohydrate, famy acid OR protein

9 Cellular Respira0on Breakdown of one glucose results in 36 to 38 ATP molecules Metabolic Pathway that breaks down carbohydrates Process is exergonic as high- energy glucose is broken into CO 2 and H 2 O Process is catabolic because glucose breaks into smaller molecules

10 Equa,ons for aerobic respira,on All of these are fine!...

11 Equa0on for Cellular Respira0on C 6 H 12 O 6 + 6O 2 YIELDS 6CO 2 + 6H e ATP + heat

12 REDOX reac,ons in respira,on 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

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

14 Chemical Structure of ATP Adenine Base 3 Phosphates Ribose Sugar

15 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

16 Each day, you hydrolyse ATP molecules ATP-ase ATP Synthetase

17 H 2 O HYDROLYSIS (Adding H 2 O)

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

19 Substrate level phosphoryla,on and chemiosmosis Glucose GLYCOLYSIS Pyruvic acid KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Substrate Level Phos. Substrate Level Phos. Oxida,ve Phos.

20 REDOX reac,ons in respira,on 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

21 Energy metabolism and REDOX reac,ons Metabolism is the sum of all of the chemical reac,ons in an organism: catabolic (breakdown) and anabolic (synthe,c) Respira,on is a catabolic pathway Photosynthesis is an anabolic pathway The two processes are closely linked in plants REDOX (oxida-on- reduc-on) reac-ons 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

22 REDOX reac,ons OXIDATION Loss of electrons Gain of oxygen Loss of hydrogen Results in C- O bonds Results in a compound with lower poten,al energy REDUCTION Gain of electrons Loss of oxygen Gain of hydrogen Results in C- H bonds Results in a compound with higher poten,al energy OIL RIG LEO says GER

23 Hydrogen carriers such as NAD + shumle electrons in redox reac,ons Enzymes remove electrons from glucose molecules and transfer them to a coenzyme OXIDATION Dehydrogenase and NAD + REDUCTION

24 Redox reac,ons release energy when electrons fall from a hydrogen carrier to oxygen 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 quan,,es Energy released and now available for making ATP ELECTRON CARRIERS of the electron transport chain Electron flow

25 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 (glycoysis) and in matrix of the mitochondrion

26 Two mechanisms generate ATP 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 oxida0ve phosphoryla0on Membrane Energy from Electron transport chain ATP synthase ATP synthase uses gradient energy to make ATP High H+ concentration Low H+ concentration Figure 6.7A

27 Stages of Cellular Respira0on 1. Glycolysis ALWAYS OCCURS 2. Anaerobic pathways if no oxygen available (Lac?c acid and Ethanol fermenta?on) 3. Aerobic pathways if oxygen available (Link reac?on, Krebs cycle, electron transport chain)

29 Where Does Cellular Respira0on Take Place? glycolysis occurs in the cytoplasm Krebs Cycle & ETC Take place in the mitochondria

31 Glycolysis: Always the ini-al stage of respira-on Loca,on: cytoplasm Substrate: glucose Requires input of 2 ATP Products: pyruvate, (NADH), 4 ATP Glycolysis is an anaerobic process: no oxygen required the movie...

32 Glycolysis

33 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 phosphoryla,on, lysis, oxida,on and ATP forma,on 6. Controlled by enzymes: when ATP levels in the cell are high, feedback inhibi,on will block the first enzyme in the pathway 7. Produces 2 pyruvate molecules at the end

34 If no oxygen is available, glycolysis (anaerobic) is followed by fermenta,on (anaerobic)

35 Why fermenta,on? In the absence of oxygen, glycolysis soon stops unless there is an acceptor for the electrons produced from the glycoly,c pathway

36 Fermenta0on 1. Alcoholic fermenta0on Pyruvate is converted into ethanol plus carbon dioxide and NAD + 2. Lactate fermenta0on Pyruvate is converted into lactate and NAD +

37 Alcoholic fermenta,on in yeast

38 Alcoholic fermenta,on in yeast Pyruvate is produced from glycolysis 3- carbon pyruvate is converted to 2- carbon ethanol and carbon dioxide Genera,on of carbon dioxide helps bread products to rise Yeast is used to produce ethanol

39 Lactate fermenta,on in mammals Lactate is a 3- carbon molecule NAD + is regenerated to allow glycolysis to con,nue

40 Aerobic respira,on: Higher level 8.1.4: Explain aerobic respira,on: the Link reac,on, the Krebs cycle, the role of NADH and H +, the electron transport chain and the role of oxygen 8.1.5: Explain oxida,ve phosphoryla,on in terms of chemiosmosis

(28 38 ATP): 90% of total ATP from respira0on Also produces

41 Aerobic respira,on Takes place in the mitochondria of eukaryo,c cells Substrate: pyruvate Produces LOTS of ATP (28 38 ATP): 90% of total ATP from respira0on Also produces carbon dioxide, water and heat Oxygen is the final electron acceptor

42 Aerobic respira,on 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 respira,on completely oxidises glucose Anaerobic respira,on does not completely oxidise glucose ethanol, lactate and carbon dioxide are by- products

43 Get to know your mitochondrial structure!

45 Stages of aerobic respira,on 1. The link reac,on 2. The Krebs cycle 3. The electron transport chain 4. Chemiosmosis and oxida,ve phosphoryla,on

46 Challenge 1: Explain the Link reac,on 1. Where does it take place? 2. What are the substrates? 3. What are the products? 4. How is the Link reac-on mediated? 5. Is the Link reac-on an aerobic or an anaerobic process?

47 Challenge 2: Explain the Krebs Cycle 1. Where does it take place? 2. What are the substrates? 3. What are the products? 4. How is it mediated? 5. It is considered an aerobic or an anaerobic pathway?

48 The Link Reac,on Steps 2 in aerobic respira,on (step 1 is glycolysis in the cytoplasm) ASer glycolysis, when there is ample oxygen 2 pyruvate molecules from glycolysis move into the matrix of the mitochondrion for the Link reac,on and the Krebs cycle

49 Matrix Link Reac,on 2 Krebs Cycle 2

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

51 The Krebs Cycle (Citric Acid/TCA cycle) 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

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

53 Fill in your table! Substance Oxidised/Reduced/Neither Reason NAD + NADH FADH 2 FAD

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

55 Produc,on PER glucose molecule 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

56 and finally. The electron transport chain, chemiosmosis and oxida,ve phosphoryla,on

57 The movies are on the Blog!

58 Chemiosmosis Defini,on: movement of ions across a semi- permeable membrane, down their concentra-on gradient In respira,on, chemiosmosis refers to movement of protons (hydrogen ions) down their concentra,on gradient through ATP synthase, which powers ATP synthesis

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

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

62 Chemiosmosis powers most ATP production 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

63 Ques,ons What is the role and the posi,on of oxygen in the electron transport chain? What is the benefit of having cristae in the mitochondria?

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

65 Final checks and balances Process ATP used ATP produced Net ATP gain Glycolysis Krebs cycle Electron Transport Chain/ Chemiosmosis Total

66 Final checks and balances Process ATP used ATP produced Net ATP gain Glycolysis Krebs cycle Electron Transport Chain/ Chemiosmosis Total

67 Review of mitochondrial structure and func,on Outer mitochondrial membrane Matrix Cristae Inner mitochondrial membrane Space between inner and outer membranes

68 Review of mitochondrial structure and func,on Outer mitochondrial membrane Matrix Separates contents of mitochondrion from rest of cell Like cytoplasm: enzymes for the Link reac,on and the Krebs cycle Cristae Inner mitochondrial membrane Space between inner and outer membranes Increases surface area for oxida,ve photophosphoryla,on Carriers for electron transport chain and ATP synthase and Reservoir for protons (H + ions) to create concentra,on gradient

For each glucose molecule that enters cellular respiration, respiration produces up to 38 ATP molecules Cytoplasmic fluid Electron shuttle across membranes Mitochondrion GLYCOLYSIS 2 Glucose Pyruvic

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

70 Some prac,ce ques,ons on respira,on 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)

71 Some prac,ce ques,ons on respira,on 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)

72 Some prac,ce ques,ons on respira,on 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)

73 Some prac,ce ques,ons on respira,on 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)

74 Some prac,ce ques,ons on respira,on 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)

75 Some prac,ce ques,ons on respira,on 4. State a word equation for anaerobic cell respiration in humans. (1 mark)

Cellular Respira,on. Topic 3.7 and 3.8

Cellular Respira,on. Topic 3.7 and 3.8 Cellular Respira,on Topic 3.7 and 3.8 Defini,on of cellular respira,on Controlled release of energy from organic compounds to produce ATP Chemical energy is stored in covalent bonds Cells break down organic