Cellular Respiration

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Cellular Respiration
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Energy Flow

• photosynthesis
• carried out by plants
• uses energy from sunlight
• converts into glucose oxygen
• used in cellular respiration
• oxygen is consumed
• glucose is broken down? CO2 H2O

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Respiration

• means breathing
• cellular respiration
• exchange of gases
• O2 from environment is used CO2 is released
  removed by blood

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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

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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

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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

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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

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CoEnzymes

• NAD-niacin-nicotinamide adenine dinucleotide
• FAD-flavin adenine dinucleotide-riboflavin

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Glucose Oxidation Steps

• Glycolysis
• occurs in cytosol
• does not require oxygen
• also called anaerobic
• Krebs Cycle
• occurs in mitochondria
• require O2
• aerobic
• Electron Transport Chain
• occurs in mitochondria
• require O2
• aerobic

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Glycolysis

• first step in complete oxidation of glucose
• occurs in cytosol
• begins when enzyme phosphorylates glucose
• adds PO4 group to glucose? Glu6PO4
• traps glucose
• reaction uses 2 ATPs
• Energy Investment Phase

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Glycolysis

• Sugar Splitting Stage
• 6 carbon compound?2 pyruvates (3 carbon compounds)

ATP
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Glycolysis
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Pyruvate

• fate depends on oxygen availability
• not enough oxygen
• NAD is regenerated by converting pyruvate?lactic
  acid
• anaerobic fermentation
• O2 available
• pyruvic acid enters aerobic pathways of Krebs
  cycle
• aerobic respiration

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Anaerobic Fermentation

• not enough oxygen
• NAD regenerated by converting pyruvate?lactic
  acid
• limited by buildup of lactic acid
• produces acid/base problems
• degrades muscle performances
• used for short bursts of high level activity
  lasting several minutes
• cannot supply ATP for long, endurance activities

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Alcohol Fermentation

• yeast without oxygen
• provides ATP
• by product-ethanol
• regenerates NAD

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Aerobic Respiration

• pyruvic acid enters mitochondria
• once inside? converted ?acetyl CoA
• during conversion
• pyruvate is decarboxylated (carbons removed)
  released as CO
• pyruvic acid NAD coenzyme A? CO2 NADH
  Acetyl CoA

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Krebs Cycle

• acetyl CoA enters Krebs Cycle
• 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

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Krebs Cycle

• Yields
• 2 CO2
• reducing equivalents-3 NADH 1 FADH2
• further oxidized in electron transport chain
• 1 GTP-ATP equivalent
• Since two pyruvates are obtained from oxidation
  of glucose? amounts need to be doubled for
  complete oxidation results

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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

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Oxidative Phosphorylation/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 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

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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 fuelschemi
• 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
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Oxidative Phosphorylation

• for each pair of electrons removed by NAD from
  substrate 3 ATPs are made
• FAD?2 ATPs are made

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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 324 ATP
• 2 FADH2 X 24 ATP
• 2 moles pyruvate?2 NADH H-glycolysis ?2 X 2
  4 ATP
• Total 36 ATP