InhibitorsMetabolismBiochemical pathwaysRespirationRedoxRespirationElectron carriersATPOxidation of glucoseGlycolysisNADH must be recycledFate of pyruvatePyruvate OxidationProducts of pyruvate oxidationKrebs cycleSo far….Electron transport chain (ETC)ChemiosmosisEnergy yield of respirationRegulation of respirationOxidation without O2Anaerobic respirationFermentationCatabolism of proteinCatabolism of FatEvolution of metabolismPhotosynthesisChloroplastStagesDiscovery of PhotosynthesisPigmentsAbsorption spectrumPigments of photosynthesisChlorophyllsChlorophyll structurePhotosystem organizationAntenna complexReaction centerLight-dependent reactionsCyclic photophosphorylationChloroplasts have two connected photosystemsNoncyclic photophosphorylationPhotosystem IIPhotosystem IChemiosmosisProduction of additional ATPCarbon Fixation – Calvin CycleCalvin CycleCalvin Cycle: Three PhasesOutput of Calvin cycleEnergy cyclePhotorespirationTypes of photosynthesisC4 plantsCAM plantsCompare C4 and CAMInhibitors Competitive-Competes with substrate for active site Noncompetitive- Binds to enzyme at a site other than the active siteFeedback inhibition End-product of pathway binds to an allosteric site on enzyme that catalyzes first reaction pathway. Shuts down pathway so raw materials and energy aren’t wasted.Metabolism Total of all chemical reactions carried out by an organism Anabolic reactions/ anabolism: expend energy to build up molecules Catabolic reactions/catabolism: Harvest energy by breaking down moleculesBiochemical pathways Occur in a sequence  Product of one reaction is a substrate for the next  Many steps occur in the organellesChapter 7Respiration Organisms can be classified based on how they obtain energy Autotrophs- make their own food Heterotrophs- obtain energy from other organisms All organisms use cellular respiration to extract energy from organic moleculesRedox Electrons and energy Nicotinamide adenosine dinucleotide (NAD+) NAD+: electron carrier, accepts 2 electrons and 1 proton to become NAD, and is reversibleRespiration Aerobic- final electron receptor is oxygen Anaerobic- final electron acceptor is an inorganic molecule Fermentation- final electron acceptor is an organic molecule C6H12O6+6O26CO2+6H20+energy ∆G=-686 kcal/mol of glucoseElectron carriers Many types of carriers can be used- soluble, membrane-bound, move within membrane All carriers can be easily oxidized and reduced Some carry electrons, some electrons and proteins NAD+ acquires 2 electrons and a proton to become NADHATP Cells use ATP to drive endergonic reactions  ∆G=-7.3 kcal/mol Two mechanisms for sythensis:1. Substrate level phosphorylation- transfer phosphate group to ADP-glycolysis2. Oxidative phosphorylation- ATP synthanse uses energy from a proton gradientOxidation of glucose Complete oxidation of glucose proceeds in stages1. Glycolysis2. Pyruvate oxidation3. Krebs cycle (citric acid cycle)4. Electron transport chain & chemiosmosis Glycolysis Converts 1 glucose (6 carbons) to 2 pyruvate (3 carbons) 10-steps Occurs in cytoplasm  Net production of 2 ATP molecules by substrate-level phosphorylation 2 NADH produced by the reduction of NAD+NADH must be recycled For glycolysis to continue, NADH must be recycled to NAD+ by either1. Aerobic respiration:- Oxygen is available as the final electron acceptor- Produces significant amount of ATP2. Fermentation:- Occurs when oxygen is not available - Organic molecule is the final electron acceptorFate of pyruvate Depends on oxygen availability- When oxygen is present, pyruvate is oxidized to acetyl-CoA which enters the krebs cycleo Aerobic respiration- Without oxygen, pyruvate is reduced in order to oxidize NADH back to NAD+ o FermentationPyruvate Oxidation In the presence of oxygen, pyruvate is oxidized- Occurs in the mitochondria in eukaryoteso Multienzyme complex called pyruvate dehydrogenase catalyzes the reaction- Occurs at the plasma membrane in prokaryotesProducts of pyruvate oxidation For each 3- carbon pyruvate molecule: - 1 CO2 o Decarboxylation- 1 NADH- 1 acetyl-CoA which consists of 2 carbons from pyruvate attached to coenzyme Ao Acetyl-CoA proceeds to the Krebs cycleKrebs cycle Oxidizes the acetyl group from pyruvate Occurs in the matrix of the mitochondria Biochemical pathway of 9 steps in 3 segments1. Acetyl-CoA+OxaloacetateCitrate2. Citrate rearrangement and decarboxylation3. Regeneration of oxaloacetate For each acetyl- CoA entering:- Release 2 molecules of CO2- Reduce 3 NAH+ to 3 NADH- Reduce 1 FAD (electron carrier) to FADH2- Produce 1 ATP- Regenerate oxaloacetateSo far…. Glucose has been oxidized to:- 6 CO2- 4 ATP- 10 NADH- 2 FADH- Electron carriers proceed to the electron transport chain- Electron transfer has released 53 kcal/mol of energy by gradual energy extraction- Energy will be put to use to manufacture ATPElectron transport chain (ETC) A series of membrane- bound electron carriers Embedded in the inner mitochondrial membrane Electrons from NADH and FADH2 are transferred to complexes of the ETC  Each complex- A proton pump creating proton gradient- Transfers electrons to next carrierChemiosmosis Accumulation of protons in the intermembrane space drives protons into the matrix via diffusion Membrane relatively impermeable to ions Most protons can only reenter matrix through ATP synthase- Uses energy of gradient to make ATP from ADP+PiEnergy yield of respiration Theoretical energy yield - 38 ATP per glucose for bacteria- 36 ATP per glucose for eukaryotes Actual yield:- 30 ATP per glucose for eukaryotes- Reduced yield is due to:o “leaky” inner membraneo Use of the proton gradient for purposes other than ATP synthesisRegulation of respiration  Example of feedback inhibition 2 key control points1. In glycolysiso Phosphofructokinase is allosterically inhibited by ATP and/or citrate 2. In pyruvate oxidationo Pyruvate dehydrogenase inhibited by high levels of NADHo Citrate synthetase inhibited by high levels of ATPOxidation without O21. Anaerobic respiration- Use of inorganic molecules (other than O2) as final electron acceptor- Many prokaryotes use sulfur, nitrate, carbon dioxide or even inorganic molecules2. Fermentation- Use of organic molecules as final electron acceptorAnaerobic respiration Methanogens- CO2 is reduced to CH4 (methane)- Found in diverse