Cell respiration and photosynthesis IB Biology

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IB Biology Cell Respiration HL

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Cell respiration and photosynthesis IB Biology

  1. 1. CELL RESPIRATION
  2. 2. REACTIONS OXIDATIONOXIDATION • Addition of oxygenAddition of oxygen atomsatoms • Removal of hydrogenRemoval of hydrogen atomsatoms • Loss of electrons fromLoss of electrons from a substancea substance REDUCTIONREDUCTION • Removal of oxygenRemoval of oxygen atomsatoms • Addition of hydrogenAddition of hydrogen atomsatoms • Addition of electronsAddition of electrons to a substanceto a substance
  3. 3. RESPIRATIONRESPIRATION GLUCOSEGLUCOSE FATTY ACIDSFATTY ACIDS AMINO ACIDSAMINO ACIDS OXIDATIONOXIDATION GLYCOLYSISGLYCOLYSIS •IF THE RESPIRATORY SUBSTRATE IS GLUCOSE THEN THE FIRST STAGE OF CELLULAR RESPIRATION IS GLYCOLYSIS •THIS PATHWAY OCCURS IN THE CYTOPLASM •LESS AMOUNT OF ENERGY IS PRODUCED •PARTIAL OXIDATION OF GLUCOSE OCCURS, AND DOES NOT REQUIREDOES NOT REQUIRE OXYGENOXYGEN •IT OCCURS IN BOTH AEROBIC AND ANAEROBIC RESPI RATION. •IT OCCURS IN BOTH PROKARYOTES & EUKARYOTES
  4. 4. STEPS INVOLVED IN GLYCOLSISSTEPS INVOLVED IN GLYCOLSIS STEP I PHOSPHORYLATIONSTEP I PHOSPHORYLATION • 2PO2PO44 groups are added to agroups are added to a GLUCOSEGLUCOSE molecule tomolecule to formform HEXOSE BIPHOSPHATEHEXOSE BIPHOSPHATE.. • 2ATP2ATP molecules provide themolecules provide the POPO44 • Energy level of the hexose formed is raised byEnergy level of the hexose formed is raised by phosphorylation and this makes the subsequentphosphorylation and this makes the subsequent reactions possiblereactions possible GLUCOSEGLUCOSE HEXOSEHEXOSE BIPHOSPHATEBIPHOSPHATE 2 ATP2 ATP 2 ADP2 ADP
  5. 5. STEP II: LYSISSTEP II: LYSIS • EachEach HEXOSE BIPHOSPHATEHEXOSE BIPHOSPHATE splits to formsplits to form 22 molecules ofmolecules of TRIOSE PHOSPHATE .TRIOSE PHOSPHATE . HEXOSEHEXOSE BIPHOSPHATEBIPHOSPHATE 2 molecules2 molecules TRIOSETRIOSE PHOSPHATEPHOSPHATE
  6. 6. STEP III: OXIDATION of Triose phosphateSTEP III: OXIDATION of Triose phosphate 2 molecules of2 molecules of TRIOSETRIOSE PHOSPHATEPHOSPHATE 3 CARBON3 CARBON COMPOUNDCOMPOUND carryingcarrying 2PO2PO44 groups eachgroups each 2 NAD2 NAD++ 2 NADH + H2 NADH + H++
  7. 7. STEP IV: ATP formationSTEP IV: ATP formation TwoTwo 33 CARBONCARBON COMPOUNDCOMPOUND formedformed 2 PYRUVATE2 PYRUVATE MOLECULESMOLECULES 4 ADP4 ADP 4 ATP4 ATP Enzymes remove the 2 phosphate groups and provide them to ADP for ATP formation
  8. 8. STEP IV: ATPSTEP IV: ATP formationformation STEPS INVOLVED IN GLYCOLSISSTEPS INVOLVED IN GLYCOLSIS STEP III: OXIDATION of Triose phosphateSTEP III: OXIDATION of Triose phosphate STEP II: LYSISSTEP II: LYSIS STEP I: PHOSPHORYLATIONSTEP I: PHOSPHORYLATION glucoseglucose HexoseHexose biphosphate (6c)biphosphate (6c) 2 triose phosphate2 triose phosphate (3c) molecules(3c) molecules 2 pyruvate2 pyruvate moleculesmolecules 2 ATP2 ATP 2 ADP2 ADP 2 INTERMEDIATE2 INTERMEDIATE (3c) molecules(3c) molecules 4 ADP4 ADP 4 ATP4 ATP 2 NAD2 NAD++ 2 NADH + H2 NADH + H++
  9. 9. • The fate of Pyruvate is decided by theis decided by the availability of oxygen.availability of oxygen. • This step occurs only if oxygen is notnot available or is in short supply; ie . ANAEROBIC RESPIRATION Each molecule ofEach molecule of PYRUVATEPYRUVATE Ethanol (2 C)Ethanol (2 C) COMPOUNDCOMPOUND COCO22In plantsIn plants In animalsIn animals
  10. 10. In animalsIn animals LINK REACTIONLINK REACTION
  11. 11. LINK REACTION • Pyruvate passes from the cytosol to the innerpasses from the cytosol to the inner mitochondrial matrixmitochondrial matrix by active transport • This step occurs only if oxygen is available; ie . AEROBIC RESPIRATION Each moleculeEach molecule ofof PYRUVATEPYRUVATE 2 CARBON2 CARBON COMPOUNDCOMPOUND ACETYL CoAACETYL CoA NADNAD++ NADH + HNADH + H++ COCO22CoACoA
  12. 12. • DeCarboxylationDeCarboxylation and OxidationOxidation occur simultaneously hence the step is called OxidativeOxidative decarboxylationdecarboxylation • Pyruvate + CoA forms Acetyl CoAAcetyl CoA • CoACoA comprises of [ adenine + ribose sugar + Pantothenic acid]comprises of [ adenine + ribose sugar + Pantothenic acid] • CoA is a carrier for Acetyl group into the Krebs cycle. NADNAD++ NADH + HNADH + H++ COCO22 CoACoACoACoA Link reactionLink reaction
  13. 13. • The energy stored in NADH is used to generateThe energy stored in NADH is used to generate a proton gradient across the inner membrane.a proton gradient across the inner membrane. • The energy of the proton gradient is used toThe energy of the proton gradient is used to make ATP (phosphorylate).make ATP (phosphorylate). • Glucose on oxidation during glycolysis andGlucose on oxidation during glycolysis and Krebs cycle , the Co-enzymes NAD and FAD areKrebs cycle , the Co-enzymes NAD and FAD are reduced toreduced to NADH + HNADH + H++ & FADH + H& FADH + H++ Oxidation phosphorylationOxidation phosphorylation
  14. 14. • In the mitochondrial matrix electrons fromIn the mitochondrial matrix electrons from NADH are transferred to Co Q by NADHNADH are transferred to Co Q by NADH DEHYDROGENASE; energy is releasedDEHYDROGENASE; energy is released • As a result the H+ ions ( protons) areAs a result the H+ ions ( protons) are transferred to the inter membrane space.transferred to the inter membrane space.
  15. 15. • Co Q carries the electrons to cytochrome bc1Co Q carries the electrons to cytochrome bc1 complex ; energy is releasedcomplex ; energy is released • Electrons are carried forward from cytochromeElectrons are carried forward from cytochrome bc1 complex to cytochrome c ; energy isbc1 complex to cytochrome c ; energy is releasedreleased • As a result the more and more H+ ionsAs a result the more and more H+ ions ( protons) are transferred to the inter( protons) are transferred to the inter membrane space.membrane space.
  16. 16. • In the mitochondrial matrix electrons fromIn the mitochondrial matrix electrons from FADH are transferred to Co Q; energy isFADH are transferred to Co Q; energy is releasedreleased • As a result the H+ ions ( protons) areAs a result the H+ ions ( protons) are transferred to the inter membrane space.transferred to the inter membrane space.
  17. 17. • Co Q carries the electrons to cytochrome bc1Co Q carries the electrons to cytochrome bc1 complex ; energy is releasedcomplex ; energy is released • Electrons are carried forward from CytochromeElectrons are carried forward from Cytochrome C to Cytochrome c oxidase; energy is releasedC to Cytochrome c oxidase; energy is released • As a result the more and more H+ ionsAs a result the more and more H+ ions ( protons) are transferred to the inter( protons) are transferred to the inter membrane space.membrane space. Cytochrome c oxidase ultimately transfersCytochrome c oxidase ultimately transfers electrons to Oxygen (terminal e acceptor) andelectrons to Oxygen (terminal e acceptor) and water is formed as an end product.water is formed as an end product.
  18. 18. • Transfer of protons to the inter membraneTransfer of protons to the inter membrane space develops a proton motive force across thespace develops a proton motive force across the membrane.membrane. • Inner membrane is impermeable to protons soInner membrane is impermeable to protons so protons can pass through into the matrix is onlyprotons can pass through into the matrix is only through the ATP Synthase enzyme.through the ATP Synthase enzyme. Energy derived from the movement ofEnergy derived from the movement of these protons back into the inner matrixthese protons back into the inner matrix is used to synthesize ATP from ADPis used to synthesize ATP from ADP This is oxidative phosphorylation.This is oxidative phosphorylation.
  19. 19. Respiration chemiosmosisRespiration chemiosmosis • Involves an electron transport chain in the membrane s of the cristae • Energy is released when electrons are exchanged from 1 carrier to another • Released energy is used to actively pump hydrogen ions into the inter-membrane space • Hydrogen ions come from the matrix • H ions diffuse back into the matrix through the channels of ATP synthase • ATP synthase catalyses the oxidative phosphorylation of ADP to ATP
  20. 20. PHOTOSYNTHESISPHOTOSYNTHESIS 6CO2 + 12 H2O  C6H12O6 + 6 H2O + 6 O2. • Draw and label the chloroplast as seen under the electron microscope • State that photosynthesis contains light dependent and light independent reactions. • Explain light dependent reactions.
  21. 21. Structure of ChloroplastStructure of Chloroplast • Chloroplast contains a double layered membrane • Like mitochondria it contains its own DNA (plasmid) and 70s ribosomes. • Stroma- matrix similar to the cytosol of the cell ; it contains enzymes and chemicals necessary for dark reaction , some lipid molecules and starch granules. • Grana- contains stacked thylakoids – flat membranous sacs containing chlorophyll pigment in units called photosystems • Membranes of the grana contain electron carriers and hold the pigment enzymes & provide a large surface area for light dependent reactions to occur.
  22. 22. The overall processThe overall process • The reactions on establishing bonds for the formation of organic molecules. • 6CO2 + 12 H2O  C6H12O6 + 6 H2O + 6 O2 • Photosynthesis is an anabolic process • Ocuurs in 2 steps LIGHT DEPENDENT STAGELIGHT DEPENDENT STAGE ( occurs in the GRANA) and LIGHT INDEPENDENT STAGELIGHT INDEPENDENT STAGE ( occurs in the STROMA)
  23. 23. The Light dependent reactions:The Light dependent reactions: • Light supplies energy for these reactions to occur • Pigments are arranged on the thylakoid membranes in a PHOTOSYSTEM (chlorophyll a , accessory pigments and protein matrix and the reaction centre (chlorophyll a , primary electron acceptor and protein matrix) • Photosystem 1 is effective at 700 nm • Photosystem II is effective at 680 nm. • They work together to bring about non cyclic electron transfer.
  24. 24. The Light dependent reactions:The Light dependent reactions: • Light strikes the Photosystem II causing it to transfer e to primary electron acceptor at the reaction centre. • Excited e travel down the ETC electron transport chain (plastoquinone to cytochrome complex), electron loses energy at each exchange. • Electrons are replaced by splitting water molecules, to produce elctrons, H+ and Oxygen atoms, this is photolysis of water. • Electrons obtained are supplied 1 by 1 to the reaction centre. • Chemiosmosis occurs , H+ are pumped into the thylakoid membrane
  25. 25. The Light dependent reactions:The Light dependent reactions: • The outflow of the H+ into the stroma via the ATP synthase enzyme causes Phosphorylation --- ATP generation from ADP and PO4 –called NON CYCLIC PHOSPHORYLATION. • Light strikes the Photosystem I causing it to transfer e to primary electron acceptor at the reaction centre. • Excited e travel down the ETC electron transport chain (INVOLVING FERREDOXIN & NADP reductase which provides 2 electrons to NADP+ & reduces it to NADPH) • NADPH & ATP are the final products of light reaction • oxygen which is a waste product is excreted .
  26. 26. Photosynthesis chemiosmosisPhotosynthesis chemiosmosis • Involves an electron transport chain in the membrane s of the thylakoids • Energy is released when electrons are exchanged from 1 carrier to another • Released energy is used to actively pump hydrogen ions into the thylakoid space • Hydrogen ions come from the stroma • H ions diffuse back into the stroma through the channels of ATP synthase • ATP synthase catalyses the oxidative phosphorylation of ADP to ATP
  27. 27. Cyclic photophosphorylationCyclic photophosphorylation • It requires photosystem Iphotosystem I, but not photosystem II.photosystem II. • Light-dependent electron transport occurs in the thylakoid membranes, where electrons follow a cyclic pathway, returning to the photosystem I reaction center. • The energy of this electron transport results in a H+ gradient formation, the energy source for ATP synthesis. ATP is formed from ADP and Pi, but NADP+ is not reduced.
  28. 28. LIGHT INDEPENDENT REACTIONSLIGHT INDEPENDENT REACTIONS • Occurs in the stroma • It involves Calvins cycle • Ribulose biphosphate (RuBP) (5c), binds to an incoming CO2 ---Carbon fixing catalyzed by enzyme RuBP carboxylase, ( rubisco) , thus forming an unstable 6C compound. • It breaks down into 2 (3c) compounds – glycerate-3-phosphate. • glycerate-3-phosphate are acted upon by ATP & NADPH from the light reactions to form 2 more compounds called TRIOSE PHOSPHATE (3c), this is reduction division. • TP may go in 2 directions , some leave the cycle to become sugar phosphates that become CELLULOSE/STARCH; while most continue in the cycle to form RuBP. • In order to regain RuBP from TP , the cycle uses ATP.

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