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CELL RESPIRATION

CELL RESPIRATION. REACTIONS. OXIDATION. REDUCTION. Removal of oxygen atoms Addition of hydrogen atoms Addition of electrons to a substance. Addition of oxygen atoms Removal of hydrogen atoms Loss of electrons from a substance. RESPIRATION. GLUCOSE FATTY ACIDS AMINO ACIDS.

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CELL RESPIRATION

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  1. CELL RESPIRATION

  2. REACTIONS OXIDATION REDUCTION Removal of oxygen atoms Addition of hydrogen atoms Addition of electrons to a substance • Addition of oxygen atoms • Removal of hydrogen atoms • Loss of electrons from a substance

  3. RESPIRATION GLUCOSE FATTY ACIDS AMINO ACIDS ATP( ENERGY CURRENCY OF THE CELL) GLYCOLYSIS OXIDATION • 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 REQUIRE OXYGEN • IT OCCURS IN BOTH AEROBIC AND ANAEROBIC RESPI RATION. • IT OCCURS IN BOTH PROKARYOTES & EUKARYOTES

  4. STEPS INVOLVED IN GLYCOLSIS STEP I PHOSPHORYLATION • 2PO4groups are added to a GLUCOSE molecule to form HEXOSE BIPHOSPHATE. • 2ATP molecules provide the PO4 • Energy level of the hexose formed is raised by phosphorylation and this makes the subsequent reactions possible HEXOSE BIPHOSPHATE 2 ATP 2 ADP GLUCOSE

  5. STEP II: LYSIS • Each HEXOSE BIPHOSPHATE splits to form 2 molecules of TRIOSE PHOSPHATE . HEXOSE BIPHOSPHATE 2 molecules TRIOSE PHOSPHATE

  6. STEP III: OXIDATION of Triose phosphate 2 NAD+ 2 NADH + H+ 3 CARBON COMPOUND carrying 2PO4 groups each 2 molecules of TRIOSE PHOSPHATE

  7. STEP IV: ATP formation 4 ADP 4 ATP Two 3 CARBON COMPOUND formed 2 PYRUVATE MOLECULES Enzymes remove the 2 phosphate groups and provide them to ADP for ATP formation

  8. STEPS INVOLVED IN GLYCOLSIS STEP I: PHOSPHORYLATION STEP II: LYSIS STEP IV: ATP formation STEP III: OXIDATION of Triose phosphate 2 NAD+ 2 NADH + H+ 2 triose phosphate (3c) molecules glucose 2 ATP 2 INTERMEDIATE (3c) molecules 2 ADP 4 ADP Hexosebiphosphate (6c) 4 ATP 2 pyruvate molecules

  9. The fate of Pyruvateis decided by the availability of oxygen. • This step occurs only if oxygen is not available or is in short supply; ie . ANAEROBIC RESPIRATION CO2 In plants Each molecule of PYRUVATE Each molecule of PYRUVATE(3C) Lactic acid (3 C) COMPOUND Ethanol (2 C) COMPOUND In animals

  10. LINK REACTION In animals Each molecule of PYRUVATE(3C) Lactic acid (3 C) COMPOUND

  11. LINK REACTION • Pyruvatepasses from the cytosol to the inner mitochondrial matrix by active transport • This step occurs only if oxygen is available; ie . AEROBIC RESPIRATION NAD+ NADH + H+ 2 CARBON COMPOUND ACETYL CoA Each molecule of PYRUVATE CO2 CoA

  12. DeCarboxylation and Oxidation occur simultaneously hence the step is called Oxidative decarboxylation • Pyruvate + CoA forms Acetyl CoA • CoAcomprises of [ adenine + ribose sugar + Pantothenic acid] • CoA is a carrier for Acetyl group into the Krebs cycle. 2 CARBON COMPOUND ACETYL CoA Each molecule of PYRUVATE NAD+ NADH + H+ CO2 CoA Link reaction summary

  13. Oxidation phosphorylation • The energy stored in NADH is used to generate a proton gradient across the inner membrane. • The energy of the proton gradient is used to make ATP (phosphorylate). • Glucose on oxidation during glycolysis and Krebs cycle , the Co-enzymes NAD and FAD are reduced to NADH + H+ & FADH + H+

  14. In the mitochondrial matrix electrons from NADH are transferred to Co Q by NADH DEHYDROGENASE; energy is released • As a result the H+ ions ( protons) are transferred to the inter membrane space.

  15. Co Q carries the electrons to cytochrome bc1 complex ; energy is released • Electrons are carried forward from cytochrome bc1 complex to cytochrome c ; energy is released • As a result the more and more H+ ions ( protons) are transferred to the inter membrane space.

  16. In the mitochondrial matrix electrons from FADH are transferred to Co Q; energy is released • As a result the H+ ions ( protons) are transferred to the inter membrane space.

  17. Co Q carries the electrons to cytochrome bc1 complex ; energy is released • Electrons are carried forward from Cytochrome C to Cytochrome c oxidase; energy is released • As a result the more and more H+ ions ( protons) are transferred to the inter membrane space. Cytochrome c oxidase ultimately transfers electrons to Oxygen (terminal e acceptor) and water is formed as an end product.

  18. Transfer of protons to the inter membrane space develops a proton motive force across the membrane. • Inner membrane is impermeable to protons so protons can pass through into the matrix is only through the ATP Synthase enzyme. Energy derived from the movement of these protons back into the inner matrix is used to synthesize ATP from ADP This is oxidative phosphorylation.

  19. Respiration 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. PHOTOSYNTHESIS 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. Structure 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. The 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 STAGE ( occurs in the GRANA) and LIGHT INDEPENDENT STAGE ( occurs in the STROMA)

  23. 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. 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. 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. Photosynthesis 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. Cyclic photophosphorylation • It requires photosystem I, but not 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. LIGHT 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 foem 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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