Cellular Respiration Harvesting Chemical Energy

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Cellular RespirationHarvesting Chemical
Energy

• Chapter 9

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Living is work

• Cells require transfusions of energy from
  outside sources to perform work
• Ecosystems, energy enters as sunlight.
• Light energy trapped in organic molecules is
  available to both photosynthetic organisms and
  others that eat them

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Catabolic Pathways Yield Energy

• Organic molecules store energy in their
  arrangement of atoms
• Metabolic pathways that release the energy stored
  in complex organic molecules are catabolic
• Types of catabolic processes
• Fermentation, leads to the partial degradation of
  sugars in the absence of oxygen
• Cellular Respiration, uses oxygen as a reactant
  to complete the breakdown of a variety of organic
  molecules

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Harvesting Stored Energy

• Carbohydrates, fats, and proteins all yield
  energy
• Glucose is used as a model
• C6H12O6 6O2 ?6CO2 6H2O ATP
• Oxidation /Reduction Process

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Coupling oxidation reduction

• Redox reactions in respiration
• release energy as break down molecules
• break C-C bonds
• strip off electrons from C-H bonds by removing H
  atoms
• C6H12O6 ? CO2 the fuel has been oxidized
• electrons attracted to more electronegative atoms
• in biology, the most electronegative atom?
• O2 ? H2O oxygen has been reduced
• release energy to synthesize ATP

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Oxidation Reduction

• Reduction
• removing O
• adding H
• gain of electrons
• stores energy
• endergonic

• Oxidation
• adding O(oxygen attracts electrons)
• removing H
• loss of electrons
• releases energy
• Exergonic
• Where do the free H go?? transferred to NAD
  FAD

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NAD? Nicotinamide adenine dinucleotide

• Cofactor ?assists enzymes, acts as an electron
  shuttle

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FAD? Flavin adenine dinucleotide

• Another cofactor that is an electron shuttle

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Energy in Food

• Not released at once, if so cant be harnessed
• Broken down in a series of steps and electrons
  are carried? final acceptor is O2

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Cellular Respiration (3 Parts)

1. Glycolysis
2. Krebs Cycle
3. Electron Transport Chain

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1. Glycolysis
Energy Investment Phase

• Takes place in the cytoplasm
• Generates ATP NADH
• Product is 2 pyruvic acid molecules(C3H4O3)
• 2ATP(4out-2in)
• 2NADH

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Phosphoglucoisomerase?converts G6P to F6p
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Phosphofructokinase/aldolase
Energy Investment Phase
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Energy Payoff Phase
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Energy Payoff Phase
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Substrate Level Phosphorylation
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Conversion of Pyruvate to Acetyl CoA
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Krebs Cycle
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Krebs Cycle? Summary
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Figure 9.6 An overview of cellular respiration
(Layer 2)
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Figure 9.6 An overview of cellular respiration
(Layer 3)
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Figure 9.8 The energy input and output of
glycolysis
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Electron Transport Chain

• Not substrate level phosphorylation
• NADH dumps electrons into the cristae walls which
  contains an electron transport system
• Members of the ETC? all but one are proteins w/
  cofactor or conenzyme (prosthetic group)
• Each carrier is more electronegative and lower in
  PE than the previous one

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Members of the ETC

• FMN? Flavin mononucleotide(Vit B), coenzy.,
  tightly bound to protein (prosthetic grp)
• FeS? protein w/iron S(prosthetic grp)
• Q? ubiquinone? only member that is a lipid,
  (ubiquitous?present everywhere)
• Cyt b? similar to hemoglobiun, but carries e,
  iron nitrogen based internal ring
• Cyt C, Cyt a

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Transfer of Electrons
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Chemiosmosis

• Takes place in the cristae membrane
• Energy in NADH FAD
• Creates a H gradient that becomes a source of PE
  ? used to do cell work

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Chemiosmosis? Couples ETC to ATP Sythesis
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ATP Synthase

• 3 compartments? hydrogen ion pore
• Rotor
• Rod
• Knob
• Energy of fall causes a change in conformation?
  ADP?ATP
• 1NADH3ATP
• 1FADH22ATP

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From Glucose to ATP
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Errors

• No Oxygen? final acceptor is oxygen, so e- cannot
  be transferred , all carriers are reduced, Krebs
  halts
• Cyanide? binds irreversibly with cytochromes,
  blocks the ETC, cell is denied of 98 energy

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Catabolism of Other Foods

• Proteins? Amino Acids? deamination? pyruvate?
  acetylCoA
• Fats? FA Gylcerol
• FA? beta oxidation breaks into 2 C
  fragments?AcetylCoA
• Glycerol? G3P(intermidiate in glycolysis)

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Fermentation

• Final electron acceptor is an organic molecule
• Takes place in the absence of oxygen
• Carried out by bacteria, yeast and other fungi
• Consists of
• Glycolysis
• Transfer of NADHs e to another compound

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Muscle Cell ?Lactic Acid Fermentation

• Lactate ? the liver? degraded to pyruvate

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Lactic Acid Fermentation

• Lactate build
• Sore muscles
• Goes to liver? changed to pyruvate
• Pyruvate? back to glucose
• Deformation of muscle proteins
• Eventually muscle will fail

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Alcohol Fermentation? Yeast
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Pyruvate ? Key Juncture in Catabolism
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Ethanol, NADH and The Liver

• Ethanol? acetaldehyde 16-18 hrs, NADH acetic
  acid?CO2H2O
• Extra NADH ? problem, feed into ETC
• NADH from glycolysis and Krebs not needeed
• Foods are converted into fats
• Fatty accum. In liver causes inflammation
• Inflammatory hepatitis leads to scar tissue?
  leads to cirrhosis

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Control of Catabolism

• Key enzyme? phosphofructokinase(pfk)
• Glucose is always phosphorylated to keep it in
  the cells, must have 2nd phosphorylation to break
  it down uses pfk
• AMP-pfk will work faster(turbo)? allosteric
  facilitation
• ADP- pfk will be working(fast)?allosteric
  facilitation
• ATP- pfkstop/slow(stop)--_ allosteric inhibition