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Cellular Respiration

Cellular Respiration. Energy Flow. photosynthesis carried out by plants uses energy from sunlight converts it into glucose & oxygen used in cellular respiration oxygen is consumed glucose is broken down into CO 2 & H 2 O. Respiration. means breathing cellular respiration

lesley-crawford
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Cellular Respiration

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  1. Cellular Respiration

  2. Energy Flow • photosynthesis • carried out by plants • uses energy from sunlight • converts it into glucose & oxygen • used in cellular respiration • oxygen is consumed • glucose is broken down into CO2 & H2O

  3. Respiration • means breathing • cellular respiration • exchange of gases • O2 from the environment is used and & CO2 is released & removed by blood

  4. Cellular Respiration • provides ATP for cellular work • called oxidation • oxidizes food molecules, like glucose, to CO2 & water • 6C6H12O2 + 6O26CO2 + 6H2O + ATP • energy is trapped in ATP

  5. Cellular Respiration-Oxidation • electrons are transferred from sugar to O2 making H2O • do not see electron transfer in equation • see changes in H ions • glucose molecule loses hydrogen atoms as it is converted to CO2 • O2 gains hydrogen atoms to form water • O2 is an electron grabber • pulls harder than other atoms to get electrons • these hydrogen movements represent electron transfers • each hydrogen atom consists of one electron and one proton • electrons move along with hydrogens from glucose to O2 • it is as if they are falling • energy is released in the process • process is possible only because of O2 • if you stop breathingno ATP would be madeall processes stopdeath 6C6H12O2 + 6O26CO2 + 6H2O + ATP

  6. Complete Oxidation of Glucose • C6H12O6 + 6O26CO2 + 6H2O • for one thing to be oxidized-another must be reduced • oxidation & reduction reactions occur together • redox reactions

  7. Oxidation/Reduction Reactions • Oxidation • H+ atoms are removed from compounds • Oxidized things lose electrons • electron lostoxidized-loses energy • Reduction • H+ atoms are added to compounds • gain electronreduced-gains energy • food fuels are oxidized-lose energy transferred to other moleculesATP • coenzymes act as hydrogen or electron acceptors • reduced each time substrate is oxidized

  8. CoEnzymes • needed in oxidation reactions • NAD+-niacin-nicotinamide adenine dinucleotide • FAD-flavin adenine dinucleotide-riboflavin

  9. Glucose Oxidation Steps • Glycolysis • occurs in cytosol • does not require oxygen • also called anaerobic • Kreb’s Cycle • occurs in mitochondria • require O2 • aerobic • Electron Transport Chain • occurs in mitochondria • require O2 • aerobic

  10. Glycolysis • first step in complete oxidation of glucose • takes place in cytosol • begins when enzyme phosphorylates glucose • adds PO4 group to glucose Glu6PO4 • traps glucose • most cells do not have enzyme to reverse reaction & lack transport system for phosphorylated sugars • ensures glucose is trapped • Glu6PO4isomerizedFru6P+ ATP  fructose-1,6-bisphosphate-Fru 1,6diP • reaction uses 2 ATPs • Energy Investment Phase

  11. Glycolysis • Glyceraldehyde-3-P dehydrogenase catalyzes NAD+ dependent oxidation of glyceraldehyde 3P2 pyruvates

  12. Glycolysis • removed H+ • picked up by NAD+NADH + H+ • Glucose + 2NAD + 2ADP + pi2 pyruvic acids + 2NADH + 2 ATP

  13. Glycolysis

  14. Pyruvate • important branch point in glucose metabolism • fate depends on oxygen availability • not enough oxygen • NAD+ is regenerated by convertingpyruvatelactic acid • anaerobic fermentation • O2 available • pyruvic acid enters aerobic pathways of Krebs cycle • aerobic respiration

  15. Anaerobic Fermentation • not enough oxygen • NAD+ regenerated by convertingpyruvatelactic acid • limited by buildup of lactic acid • produces acid/base problems • degrades athletic performances • impairs muscle cell contractions & produces physical discomfort • used for short bursts of high level activity lasting several minutes • cannot supply ATP for long, endurance activities

  16. Alcohol Fermentation • yeast without oxygen • provides ATP • by product-ethanol • regenerates NAD+

  17. Aerobic Respiration • pyruvic acid enters mitochondria • once inside converted acetyl CoA • during conversion • hydrogen atoms of pyruvate are removed by coenzymes • pyruvate is decarboxylated (carbons removed) released as CO2diffuses out of cells into bloodexpelled by lungs • pyruvic acid + NAD + + coenzyme A CO2 + NADH + Acetyl CoA

  18. Acetyl CoA • major branch point in metabolism • 2 carbons can be converted into fatty acids, amino acids or energy

  19. Krebs Cycle • Acetyl CoA enters Krebs Cycle • also tricarboxylic acid cycle or Citric Acid Cycle • during cycle hydrogen atoms are removed from organic moleculestransferred to coenzymes • cycle begins & ends with same substrate: oxaloacetate (OAA) • acetyl CoA condenses with oxaloacetate- 4 carbon compoundcitrate-6 carbon compound • cycle continues around through 8 successive step • during steps atoms of citric acid are rearranged producing different intermediates called keto acids • eventually turns into OAA

  20. Krebs Cycle • complete revolution per acetyl CoA includes 2 decarboxylations & 4 oxidations • Yields • 2 CO2 • reducing equivalents-3 NADH & 1 FADH2 • further oxidized in electron transport chain • 1GTP-ATP equivalent Since two pyruvates are obtained from oxidation of glucose amounts need to be doubled for complete oxidation results

  21. Electron Transport Chain • transfers pairs of electrons from entering substrate to final electron acceptor-oxygen • electrons are led through series of oxidation-reduction reactions before combining with O2 atoms • reactions takes place on inner mitochondrial membrane • only permeable to water, oxygen & CO2

  22. Electron Transport Chain • members of chain • FMN-flavin mononucleotide • Fe-S centers • copper ions • coenzyme Q • cytochromes • Sequence- b,c, a & a3

  23. OxidativePhosphorylation/Electron Transport Chain System • responsible for 90% of ATP used by cells • basis-2H + O22 H20 • releases great deal of energy all at once • cells cannot handle so much energy at one time • reactions occur in series of steps • Oxidation reactions • remove H+ atoms & lose energy (H+) • Oxidized things lose electrons • compounds that gain electrons reduced-gain energy • enzymes cannot accept H atoms • Coenzymes needed to accept hydrogens • when coenzyme accepts hydrogen atoms coenzyme reduced & gains energy

  24. Oxidative Phosphorylation • Step 1: coenzyme strips pair of hydrogen atoms from substrate • FADH2 is reduced • FAD accepted 2 hydrogens & 2 electrons in TCA cycle • NADH accepted 2 electrons • bound one as hydrogen atom • Step 2: NADH & FADH2 deliver hydrogen atoms to coenzymes in inner mitochondrion membrane • one of 2 paths can be taken depending on donor • Step 3: conenzyme Q accepts hydrogen atoms from FADH2passes electrons to cytochromes • hydrogen atoms released as hydrogen ions-H+ • Step 4: electrons passed along energy lost at each step as passed from cytochrome to cytochrome • released as hydrogens • Step 5: oxygen atom accepts electron creating oxygen ion O- which has strong affinity for H+combinesH2O • does not produce ATP directly • creates conditions needed for ATP production

  25. Chemiosmosis • ETC creates conditions needed for ATP production by creating concentration gradient across inner mitochondrial membrane • as energy is released-as electrons are transferred  drives H ion pumps that move H across membrane into space between 2 membranes • pumps create large concentration gradients for H • H ions cannot diffuse into matrix because not lipid soluble • channels allow H ions to enter matrix • Chemiosmosis • energy released during oxidation of fuels=chemi • pumping H ions across membranes of mitochondria into inter membrane space =osmo • creates steep diffusion gradient for Hs across membrane • when hydrogens flow across membrane, through membrane channel proteinATP synthase attaches PO4 to ADP ATP ATP synthase

  26. Oxidative Phosphorylation • for each pair of electrons removed by NAD from substrate in TCA cycle6 hydrogen ions are pumped across inner membrane of mitrochondria makes 3 ATP • FAD4 hydrogens pumped across2 ATP

  27. Energy Yield • aerobic metabolism generates more ATP per mole of glucose oxidized than anaerobic metabolism • Glycolysis • net 2 ATPs • Krebs Cycle • 2 ATP • 8 NADH + H+ X 3=24 ATP • 2 FADH2 X 2=4ATP • 2 moles pyruvate2 NADH + H+-glycolysis 2 X 2 = 4 ATP • Total 36 ATP

  28. Metabolism Overview

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