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Cellular Respiration Decarboxylation Kreb’s Oxidative Phosphorylation Reading Photosynthesis Autotrophs Chloroplast histology Light Reactions Dark Reaction C-4 & CAM plants Homework Ch 9: Cellular Respiration Ch 10: Photosynthesis Ch 12 Prequiz Ch 13 prequiz Ch 14 Prequiz Test 1 Postponed to Oct 10 Q&A Wed 10/5 Cell Respiration Oxidation of C and Reduction of O Reduction C6H12O6 + 6 O2 Oxidation 6 CO2 + 6 H2O + Energy (ATP + heat) ΔG° = - 686 kcal/mole But broken down in a more controlled release Stepwise oxidation Each step releases significant energy Nothing 100% efficient Fig. 9-5 Electron shuttling by: H2 + 1/2 O2 1/ O 2 2 2H (from food via NADH) 2 H+ + 2 e– Controlled release of energy for synthesis of ATP Explosive release of heat and light energy Flour Mill explosions (a) Uncontrolled reaction 1/ O 2 2 (b) Cellular respiration Fig. 9-6-3 The Stages of Cellular Respiration Electrons carried via NADH and FADH2 Electrons carried via NADH Glycolysis Pyruvate Glucose Citric acid cycle Pyruvate oxidation Oxidative phosphorylation: electron transport & chemiosmosis Mitochondrion Cytosol ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation Glycolysis • • • • Cytosol Simplest metabolic pathway Most cells do it Considered most primitive biochem process mitochondria not needed • 10 steps 10 enzymes Glycolysis : Splitting of sugar 2 phases Investment Phase 4 ADP & 2 NAD+ 2 ATP Glucose Payoff phase 2 G3P (C3) (C6) 2 ADP BPG 2Pyruvate (C3) 4 ATP 2 NADH + H+ Investment Phase Coupling C D ΔG° = 5 kcal/mol ATP ADP + Pi ΔG° = -7.3kcal/mol C + ATP D + ADP + Pi ΔG° = -2.3kcal/mol E F ΔG° = 14 kcal/mol Cannot be coupled to ATP, but maybe another reaction G H ΔG° = -3 kcal/mol Can be coupled but probably isn’t because it is already spontaneous Which of the following is a possible ΔG? a)-4 b)1 c)2 d)3 Which of the following is a possible ΔG for ONLY: Pi + Glu G6P Remember you coupled this to ATP hydrolysis a)-5 b)3 c)8 d)11 ATP ADP + Pi ΔG°= -7.3 kcal/mole ATP + Glu G6P + ADP ΔG° < 0 Fig. 9-8 Glucose CO2 Glycolysis Kreb’s ΔG° -686 kcal/mol Oxidative Phosphorylation 4 ADP & 2 NAD+ 2 ATP Glucose 2 G3P 2 ADP 2Pyruvate 4 ATP 2 NADH + H+ Glucose Pyruvate ΔG° -140 kcal/mol Glycolysis : Energy investment phase Glucose + 2ATP 2 G3P + 2 ADP Use up 2 ATP because: Glucose + Pi 2ATP 2 G3P ΔG is positive 2 ADP + 2 Pi •Also “priming” G6P allow more glucose into the cell & Blocks glucose from leaking out •2nd ATP Hydrolysis step is essentially irreversible committing molecule to the rest of glycolysis How many total ATP are produced during glycolysis? Payoff phase Investment Phase 4 ADP & 2 NAD+ 2 ATP Glucose a)-2 b)4 c)10 d)32 2 G3P 2 ADP 2Pyruvate 4 ATP 2 NADH + H+ How many NET ATP are produced during glycolysis? a)-2 b)2 c)10 d)32 Payoff phase 1st oxidation step oxidized •Dehydrogenase NAD+ involved Oxidation of C Coupled to reduction of NAD+ Glyceraldehyde3-phosphate 2 x 2 NAD+ 2 NADH aka G3P GAP PGAL 6 Triose phosphate dehydrogenase 2Pi + 2 H+ •Large energy release 2 x 1, 3-Bisphosphoglycerate BPG For G3P +Pi BPG? What is a feasible G? Remember: NAD+ NADH + H+ ΔG° = 53 kcal/mole Glyceraldehyde3-phosphate 2 x 2 NAD+ a)-61 2 NADH 6 Triose phosphate dehydrogenase 2Pi + 2 H+ b)-8 c)-2 d)+40 2 x 1, 3-Bisphosphoglycerate G3P +Pi BPG ΔG° = ? NAD+ NADH + H+ ΔG° = 53 kcal/mole G3P + NAD+ BPG + NADH + H+ a)-61 b)-8 c)-2 d)+40 oxidized R-CHO R-COOH NAD+ NADH ΔG° -10.3 kcal/mol Only that it is neg is important Glyceraldehyde3-phosphate 2 x 2 NAD+ 2 NADH 6 Triose phosphate dehydrogenase 2Pi + 2 H+ 2 x 1, 3-Bisphosphoglycerate BPG Fig. 9-9-6 2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 1, 3-Bisphosphoglycerate 2 ADP 2 3-Phosphoglycerate ΔG° 7.3 2 ATP 2 ΔG° -7.3 kcal/mol 7 Phosphoglycerokinase 3-Phosphoglycerate Overall ΔG° -0.1 kcal/mol Substrate level phosphorylation Transfer of a phosphate from substrate to ADP to generate ATP R-P + ADP R + ATP • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation • Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration Pi + ADP ATP Fig. 9-9-9 2 NAD+ Substrate Phosphorylation 6 Triose phosphate dehydrogenase 2 Pi 2 NADH + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 Phosphoenolpyruvate ΔG° -15 kcal/mol 2 ADP 2 3-Phosphoglycerate 8 Phosphoglyceromutase 2 ATP 2 10 Pyruvate kinase 2-Phosphoglycerate 9 2 H2O Enolase 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 2 Pyruvate Pyruvate 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 Pyruvate What is a possible free energy change (ΔG) of phosphoenolpyruvate to pyruvate? PEP pyruvate + Pi a)+5 kcal/mole b)0 c) -5 d)-12 e)None of the above What is the primary mechanism of ATP generation in glycolysis? a)ATP b)NADP c) substrate level phosphorylation d)pyruvate Which of the following is NOT a product of glycolysis? a)ATP b)NADP c)Lactic Acid d)Pyruvate Lactic acid fermentation 2 ADP + 2 P i Glucose 2 ATP Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate Lactic acid fermentation • In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce Why does a cell use fermentation? a)To produce ATP b) To produce lactic acid c)To produce NAD+ d)To produce NADH Fig. 9-8 How equilibrium affects Respiration Normally (under aerobic conditions): •Glucose resupplied •Pyruvate & NADH used in next step NADH + H+ NAD+ •ATP used for work Anaerobic conditions (NO O2): •Pyruvate & NADH not used (O2 is required) • “Run out” of NAD+ Net Glucose 2 ADP + 2 Pi 2 NAD+ + 4 e– + 4 H+ 2 Pyruvate + 2 H2O 2 ATP 2 NADH + 2 H+ Alcohol fermentation 2 ADP + 2 Glucose P i 2 ATP Glycolysis 2 Pyruvate 2 NAD+ 2 Ethanol 2 NADH + 2 H+ 2 CO2 2 Acetaldehyde Many other forms including production of methane and hydrogen gas What is the enzyme for alcohol fermentation? a)Kinase b)Phosphotase c)Dehydrogenase d)protease ? Pyruvate decarboxylation & citric acid (or kreb’s) cycle completes the energy-yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrial Matrix • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis Pyruvate oxidation Step 1: pyruvate decarboxylation CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate 3 CO2 Coenzyme A Acetyl CoA Transport protein / pump What is the enzyme? Pyruvate Dehydrogenase Fig. 9-10 Pyruvate AcetylCoA is what kind of reaction? a)Substrate phosphorylation b)Oxidative phosphorylation c)condensation d)Redox Pyruvate dehydrogenase is likely inhibited by: Consider homeostasis Consider feedback inhibition O2 NADH Glucose NADH a)pyruvate b)ADP c)ATP d)O2 pyruvate ATP CO2 ATP is a competitive inhibitor, what will happen to the enzyme kinetics of pyruvate dehyrogenase as ATP builds up? a)Vmax will go up b)Vmax will go down c)Km will shift right d)Km will shift left Pyruvate oxidation Step 1: pyruvate decarboxylation CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate 3 CO2 Coenzyme A Acetyl CoA Transport protein Oxidation produces NADH CoA carries 2 carbon unit to citric acid cycle CO2 released Fig. 9-10 AcetylCoA is starting material for Krebs cycle • The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix (except succinate dehydrogenase which is loosely associated with inside membrane) • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn • Complete oxidation of glucose CO2 Fig. 9-12-8 CoA for next pyruvate Acetyl CoA CoA—SH NADH +H+ H2O 1 NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle 7 H2O NADH + H+ 3 CO2 Fumarate CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 Pyruvate CO2 NAD+ NADH + H+ Glycolysis 1 glucose 2 Pyruvates 2 NADH & 2ATP CoA Acetyl CoA CoA Pyruvate Decarboxylation 2 pyruvate 2 CO2 2 Acetyl CoA 2 NADH Kreb’s CoA Citric acid cycle FADH2 2 CO2 3 NAD+ 3 NADH + 3 H+ FAD ADP + P i ATP 2 Acetyl 2 turns 1 turn •2 CO2 •3 NADH + H+ •1FADH2 •ATP Total 4 CO2 6 NADH 2 FADH2 2 ATP Before the krebs cycle, most of the free energy from glucose was in: a)Pyruvate b)ATP c)NADH d)FADH After the krebs cycle, most of the free energy from glucose was in: a)CO2 b)ATP c)NADH d)FADH Fig. 9-8 Glucose CO2 Glycolysis Kreb’s ΔG° -686 kcal/mol Oxidative Phosphorylation 4 ADP & 2 NAD+ 2 ATP Glucose 2 G3P 2 ADP 2Pyruvate 4 ATP 2 NADH + H+ Glucose Pyruvate ΔG° -140 kcal/mol Lactic acid fermentation 2 ADP + 2 P i Glucose 2 ATP Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate Lactic acid fermentation • In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce Why does a cell use fermentation? a)To produce ATP b) To produce lactic acid c)To produce NAD+ d)To produce NADH Fig. 9-8 How equilibrium affects Respiration Normally (under aerobic conditions): •Glucose resupplied •Pyruvate & NADH used in next step NADH + H+ NAD+ •ATP used for work Anaerobic conditions (NO O2): •Pyruvate & NADH not used (O2 is required) • “Run out” of NAD+ Net Glucose 2 ADP + 2 Pi 2 NAD+ + 4 e– + 4 H+ 2 Pyruvate + 2 H2O 2 ATP 2 NADH + 2 H+ Alcohol fermentation 2 ADP + 2 Glucose P i 2 ATP Glycolysis 2 Pyruvate 2 NAD+ 2 Ethanol 2 NADH + 2 H+ 2 CO2 2 Acetaldehyde Many other forms including production of methane and hydrogen gas What is the enzyme for alcohol fermentation? a)Kinase b)Phosphotase c)Dehydrogenase d)protease ? Pyruvate decarboxylation & citric acid (or kreb’s) cycle completes the energy-yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrial Matrix • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis Pyruvate oxidation Step 1: pyruvate decarboxylation CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate 3 CO2 Coenzyme A Acetyl CoA Transport protein / pump What is the enzyme? Pyruvate Dehydrogenase Fig. 9-10 Coenzyme A Carries acetyl groups From vit B5 Pyruvate AcetylCoA is what kind of reaction? a)Substrate phosphorylation b)Oxidative phosphorylation c)condensation d)Redox Pyruvate dehydrogenase is likely inhibited by: Consider homeostasis Consider feedback inhibition O2 NADH Glucose NADH a)pyruvate b)ADP c)ATP d)O2 pyruvate ATP CO2 ATP is a competitive inhibitor, what will happen to the enzyme kinetics of pyruvate dehyrogenase as ATP builds up? a)Vmax will go up b)Vmax will go down c)Km will shift right d)Km will shift left Pyruvate oxidation Step 1: pyruvate decarboxylation CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate 3 CO2 Coenzyme A Acetyl CoA Transport protein Oxidation produces NADH CoA carries 2 carbon unit to citric acid cycle CO2 released Fig. 9-10 AcetylCoA is starting material for Krebs cycle • The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix (except succinate dehydrogenase which is loosely associated with inside membrane) • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn • Complete oxidation of glucose CO2 Fig. 9-12-8 CoA for next pyruvate Acetyl CoA CoA—SH NADH +H+ H2O 1 NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric acid cycle 7 H2O NADH + H+ 3 CO2 Fumarate CoA—SH 6 -Ketoglutarate 4 CoA—SH 5 FADH2 NAD+ FAD Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ CO2 Pyruvate CO2 NAD+ NADH + H+ Glycolysis 1 glucose 2 Pyruvates 2 NADH & 2ATP CoA Acetyl CoA CoA Pyruvate Decarboxylation 2 pyruvate 2 CO2 2 Acetyl CoA 2 NADH Kreb’s CoA Citric acid cycle FADH2 2 CO2 3 NAD+ 3 NADH + 3 H+ FAD ADP + P i ATP 2 Acetyl 2 turns 1 turn •2 CO2 •3 NADH + H+ •1FADH2 •ATP Total 4 CO2 6 NADH 2 FADH2 2 ATP Before the krebs cycle, most of the free energy from glucose was in: a)Pyruvate b)ATP c)NADH d)FADH After the krebs cycle, most of the free energy from glucose was in: a)CO2 b)ATP c)NADH d)FADH oxidative phosphorylation 1. electron transport & 2. ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food (Oxidation products) • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation The Pathway of Electron Transport • The electron transport chain is in the cristae of the mitochondrion • Most of the chain’s components are proteins, which exist in multiprotein complexes • The carriers alternate reduced and oxidized states as they accept and donate electrons Coenzyme Q = Ubiquinone (UQ) hydrophobic – located in membrane / Cristae Like NAD+ CoQ is an electron carrier oxidized UQ + 2H+ + 2e- reduced UQH2 Cytochromes -a, -a3, -b, -c, -c1 Heme (with iron) -containing proteins complexes also undergo Redox Diff proteins with diff hemes Free energy of electrons gradually drops • Electrons drop in free energy as they go down the chain • and are finally passed to O2 to give: 2H+ + 2e- + O2 H2O CoQ • Does NOT directly generate ATP • chain’s function is to break the large free-energy drop into smaller steps that release energy in manageable amounts Orientation does NOT match true location 40-50 proteins Complexes are H+-pumps Where does the energy for complex I proton pump come from (most directly): a)Pyruvate b)ATP c)NADH d)FADH NADH oxidation INTERMEMBRANE SPACE H+ ATP synthase Stator Rotor Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX Fig. 9-14 H+ Chemiosmosis: The Energy-Coupling Mechanism Electron transport is coupled to ATP synthesis • Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space • H+ then moves back across the membrane, passing through channels in ATP synthase • ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP • This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work Dinitrophenol (DNP) uncoupler Allows H+ to diffuse Fig. 9-17 • Gycolysis and the citric acid cycle are major intersections to various metabolic pathways • Catabolic pathways funnel many organic molecules into cellular respiration - Glycolysis accepts a wide range of carbohydrates - Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle Fig. 9-20 - Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) • Fatty acids are broken down by beta oxidation and yield acetyl CoA • An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate The Process That Feeds the Biosphere • Photosynthesis is the process that converts solar energy into chemical energy • Directly or indirectly, photosynthesis nourishes almost the entire living world Photosynthesis 6 CO2 + 6 H2O + Light energy C6H12O6 + 6 O2 6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2O Reactants: Products: 6 CO2 C6H12O6 12 H2O 6 H2O 6 O2 Remove H = oxidized Add H = reduced Light is the driving factor • electromagnetic energy, aka electromagnetic radiation • behaves as though it consists of discrete particles, called photons • travels in rhythmic waves – Wavelength is the distance between crests of waves – determines the type of electromagnetic energy A pigment abosrbs light in the blue and green spectrum. What will it look like? a) Blue b) Green c) Blue / Green d) Red / yellow Phycourobilin is orange. What colors does it absorb? a) Blue / Green b) ultraviolet c) Red d) Red / yellow 10–5 nm 10–3 nm 103 nm 1 nm Gamma X-rays rays UV 106 nm Infrared 1m (109 nm) Microwaves 103 m Radio waves Visible light 380 450 500 Shorter wavelength Higher energy 550 600 650 700 750 nm Longer wavelength Lower energy Photosynthetic Pigments: The Light Receptors • Pigments - substances that absorb visible light • Different pigments absorb different wavelengths • Wavelengths that are not absorbed are reflected or transmitted ex: Leaves appear green because chlorophyll reflects and transmits green light Fig. 10-7 Light Reflected light Chloroplast Absorbed light Granum Transmitted light Fig. 10-9 RESULTS Chlorophyll a Chlorophyll b Carotenoids (a) Absorption spectra 400 500 600 700 Wavelength of light (nm) (b) Action spectrum Aerobic bacteria Filament of alga (c) Engelmann’s experiment 400 500 600 700 Fig. 10-10 CH3 CHO in chlorophyll a in chlorophyll b Porphyrin ring: light-absorbing “head” of molecule; note magnesium atom at center Hydrocarbon tail: interacts with hydrophobic regions of proteins inside thylakoid membranes of chloroplasts Charge separation - Depart to a nearby electron acceptor Energy of electron e– Excited state Heat Photon pigments (a) Excitation of molecule Photon (fluorescence) Ground state (b) Fluorescence Fig. 10-11 The Two Stages of Photosynthesis • light reactions (the photo part) • Calvin cycle (the synthesis part) H2 O Light reactions (thylakoids): – Split H2O – Release O2 – Reduce NADP+ to NADPH – Generate ATP from ADP by photophosphorylation Light NADP+ ADP P Light Reactions Chloroplast i thylakoid membrane: 2 photosystems PS II & PS I Each Photosystem: • Chlorophyll a essential • Accessory pigments (technically nonessential) Broaden and protect Although PS II reaction-center chlorophyll a best at absorbing 680nm (called P680) Photosystem can absorb more PS I (P700)