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ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration

ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration



ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration ศึกษาเนื้อหาอื่นๆได้ที่ facebookSUK ...

ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration ศึกษาเนื้อหาอื่นๆได้ที่ facebookSUK KEE BIO



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    ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration ชีววิทยาเรื่อง การหายใจระดับเซลล์ cellular respiration Presentation Transcript

    • Energy Transformation Metabolism = total chemical reactions incells. metabole = change Metabolism is concerned with managingthe material and energy resources of the cell -Catabolism -Anabolism
    • -Catabolism is the degradative processto harvest energy from breaking down themacromolecules to simpler compounds. Cellular respiration is the main processto convert potential energy stored inmacromolecules into available energy forcellular work.
    • -Anabolism consumes energy to build orsynthesize complicated molecule from simplerones Cells use energy from catabolism todrive reactions in anabolism.
    • Energy = capacity to do work or capacityto cause specific changes -non biological systems use HEAT toperform work, but -biological systems use CHEMICALENERGY to do work
    • 2 stages of energy -potential energy =stored energy -kinetics energy = theenergy of motion Sliding down convertspotential energy tokinetics energy
    • In living cells, chemical energy is apotential energy stored in a moleculeresulting from the arrangement of atoms inthat molecules. Catabolic pathways rearrange themolecular structure of nutrients e.g.breaking down glucose to CO2 and water. As a result, the potential energy inthose nutrients is converted to kineticenergy to cause specific changes in cells.
    • Photosynthesis VS Cellular Respiration In ecosystemenergy flow andchemical recyclingbetween 2 processes:photosynthesis in thechloroplast and cellularrespiration inmitochondria.
    • ATP, cell’s energy currency, drives cellularworks.
    • Tracking Atoms through Photosynthesis Hydrogen extracted from water isincorporated into sugar and the oxygenreleased to the atmosphere (where it will beused in respiration).
    • Overview of Cellular Respiration
    • Electron Transport ChainStepwise reduction reaction to avoid explosive release of heat.
    • Glycolysis-in cytosol-glucose 2pyruvate-net result = 2ATPand 2NADH-ATP is produced bysubstrate levelphosphorylation
    • Conversion of Pyruvate to Acetyl CoA: thejunction between glcolysis and Krebs cycle 1 Pyruvate 1 Acetyl CoA + CO2 yield 1 NADH
    • Krebs Cycle-matrix ofmitochondria-1 acetyl CoAyields 3NADH + H+ 1 FADH2 1ATP 2CO2(large quantity ofelectron carriersare produced)
    • Summary of KrebsCycle1 Pyruvate yields: -3 CO2 -1 ATP fromsubstrate levelphosphorylation -4 NADH + H+ -1 FADH21 Glucose yields 2pyrvate fromGlycolysis
    • Electron Transport Chain-inner membrane ofmitochondria-electron is transferred toelectron acceptor with higheraffinity (moreelectronegative)-O2, the mostelectronegative electronacceptor, is the final electronacceptor-free energy was releasedduring electron transfer
    • Chemiosmosis: The Energy-Coupling Mechanism-innermembrane ofmitochondria is impermeableto proton (H+)-H+ was pumped across themembrane by the freeenergy released by theelectron transfer (frommatrix to the intermembranespace)= generation of protonmotive force ATP synthase
    • Chemiosmosis: The Energy-Coupling Mechanism -H+ flow back to the matrix by a channel in ATP synthase -free energy released from the H+ flow is used to synthesize ATP=Oxidative Phosphorylation ATP synthase
    • 1 NADH yields ~ 3ATP 8 NADH ~ 24 ATP 1 FADH2 yields ~ 2 ATP 2 FADH2 ~ 4ATP 2 NADH from Glycolysis have to betransported into mitochondria by the electronshuttle system to either FADH or NAD = 2-3ATP/NADH (cytosol)net = 24 + 4 + 6 or 4 = 34 - 32 ATP fromoxidative phosphorylation
    • Efficiency of Cellular Respiration G for oxidation of glucose to CO2 and H2O = - 686 kcal/mol 38ATP are generated from this process = 38 X 7.3 kcal = 277.4 kcal efficiency = 277.4 X 100 = 40% 68660% of the stored energy was lost as heat -maintain body temperature -dissipated as sweat
    • Fermentation: anaerobic process-organic compound is an electron acceptor-produce ethanol or lactate
    • Pyruvate as a Key Juncture in Catabolism
    • Catabolism of VariousMacromoleculesEvery macromoleculesare broken down intointermediates ofGlycolysis or KrebsCycle.
    • Energy transformations in biologicalsystems obey 2 fundamental laws ofthermodynamics:The first Law of Thermodynamics: the law ofconservation of energy -the energy of the universe is constant -energy can be transferred andtransformed but it can not be created ordestroyed
    • The Second Law of Thermodynamics Every energy transfer or transformationmakes the universe more disordered. Entropy is a measure of disorder orrandomness. Thus, every events in the universe havedirection = toward the increase in theentropy of the universe.e.g. -conversion of glucose to CO2 and H2O -sugar cube dissolved in a cup of water
    • The Organisms Live at the Expense of FreeEnergySpontaneous change/reaction: -occur without input of energy -increase the stability of the systemNonpontaneous change/reaction: -can occur only if energy is added to thesystem -decrease the stability of the system
    • Free energy = the portion of asystem’s energy that can perform work oris available for work when temperature isuniform throughout the system.
    • A process can occur spontaneously only if itincrease the disorder (entropy) of the universe. For biological systems the changes in bothsystems and surroundings have to be measures:unpractical.
    • Enzymes: the biological catalyst (usually = protein)-increase the rate of reaction-are not consumed by the reactions-do not change the free energy change ordirection of the reaction G = -7kcal/molThis reaction can be catalyzed by sucrase.
    • The reactantsmolecule must absorbenergy fromsurroundings to breaktheir bonds, and energyis released when thenew bonds of theproduct molecules areformed. The energy required to break bonds inreactant molecule = activation energy orfree energy of activation EA.
    • Enzymes catalyze or speed up thereaction by lower the activation energy. Enzymes cannot make endergonicreaction exergonic or cannot change G ofthe reaction.Q:Why cells do not use heat to speed up the reactions?