Ch. 9 Cellular Respiration

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Ch. 9 Cellular Respiration
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Harvesting chemical energy

• Living is lots of work
• Polymerization, Growth, highly organized, and
  movement all require energy
• Energy enters Earths ecosystems as sunlight
• Harvesting of energy requires a series of
  metabolic steps
• AEROBIC CELLULAR RESPIRATION
• Glycolysis
• Krebs cycle
• Electron transport chain

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Organic compounds

• Energy stored in chemical bonds (position)
• Enzymes help regulate this metabolism
• Organic macromolecules are rich in potential
  energy and are broken down to simpler compounds
  with less energy.
• Breaking of bonds allows work to be done.
• Organic oxygen ? carbon water energy
• compounds dioxide

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Exergonic reaction

• Organic oxygen ? carbon water energy
• compounds dioxide
• C6H12O6 6 O2 ? 6 CO2 6 H2O energy
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  (ATP heat)
• DG - 686 kcal

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Possible pathways

• Complete, aerobic cellular respiration
• Complete oxidation of carbohydrates using
• Glycolysis
• Krebs cycle and
• Electron transport chain REQUIRES OXYGEN
• Incomplete/ partial oxidation
• Gylcolysis only
• Glycolysis Lactic acid fermentation
• Glycolysis Alcoholic fermentation

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Redox reactions

• Movement of e- is what is used to store and
  release energy in bonds of organic cpds.
• Redox reactions oxidation-reduction reactions
  transfer an e- from one reactant to another
• Reduction
• Addition/receipt of e-, more negative
• Oxidation
• Loss of e- (often to O), more positive

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Falling electrons

• The step wise fall of electrons from organic
  compounds rich in bonds, to simpler compounds
  increases the entropy of the system.
• Electrons are shuttled through a series of
  carriers (membrane proteins) that allows for
  release of energy to be in small (usable)
  increments.
• Electron transport chains

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Aerobic cellular respiration

• Requires oxygen ( for e- acceptor at end of ETC)
• 3 parts
• Glycolysis ( splitting of sugar molecules )
• Some substrate level phosphorylation of ATP
• Krebs cycle ( transfer of e- to NADH, FADH)
• Some substrate level phosphorylation of ATP
• ETC ( generates ATP using ETC)
• Much oxidative phosphorylation of ATP
• Occurs in eukaryotic cells need mitochondrion
  (for Krebs and ETC) and oxygen supply for (ETC)

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Glycolysis

• Glyco sugar, glucose
• Lysis to split or break
• sugar splitting
• Cytoplasm
• ALL CELLS ! Doesnt require mitochondrion
  or O2
• 1 glucose 2 ATP and 2 NADH
• 2 ATP are net ( 4 generated 2 invested )
• Know steps on pgs. 168-169.green boxes
• Note color coding used in chapter green
  glycolysis, salmon Krebs and purple ETC

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• Summary of Steps
• Spend 1 ATP
• Add P to glucose
• 2. Glucose converted to isomer (fructose) by an
  enzyme
• 3. Spend 2nd ATP
• add 2nd P to fructose
• now in debt ( 2ATP)
• Molecule very unstable (primed)

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Summary of Steps 4. 6 C sugar cleaved into 2
3C sugars They are isomers 5. An enzyme called
isomerase converts both isomers into
glyceraldehyde (PGAL) From now on all steps are X2
PGAL
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Summary of Steps 6. Enzyme adds an inorganic
phosphate, sugar give e- and H to NAD making
NADHremember x2 7. MAKE ATP (X2) now out of
debt, organic acid 8. Relocate P ( on both
molecules)
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Summary of Steps 9. Generates water and creates
double bond. P bond now unstable 10. P leaves
adds to ADP generates more ATP (2more) now have 2
net ATP. Glucose is now split into 2 3 C
molecules PYRUVATE 2 NADH can go to ETC and make
ATP using oxidative phosphorylation
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Krebs Cycle aka Tricarboxylic Acid Cycle (TCA)
and Citric Acid Cycle

• Sir Hans Krebs 1900-1981, 1953 Nobel Prize, 1958
  knighted
• 3 C pyruvate at end of glycolysis
• Not soluble in mitochondrial membrane
• Loses C (CO2) becomes acetyl
• Creates a NADH ( stores some energy )
• Bonds to coenzyme for transport
• now Acetyl CoA
• Crosses mitochondrial membrane
• Bonds to 4C oxaloacetate to make
• 6C citrate or citric acid
• Series of steps to lose C ( makes CO2 ) and
• Store energy as NADH and FADH and ATP
• Regenerates the oxaloacetic acid. cycle

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Electron Transport Chain

• Collection of molecules embedded in the inner
  mitochondrial membrane
• Folding increases surface area ( of reactions)
• Most compounds are proteins (some pigments)
  cytochrome c used to trace DNA lineage
• Function as enzymes directing the flow of
  reactions that move e- (alternate between
  oxidized and reduced state)
• NADH and FADH2 are from Krebs and glycolysis
• NADH and FADH2 release H to these reactions
• H is split into H and e-
• The e- move through the carriers to the biggest
  e- acceptor (moving down hill releasing
  potential energy and increasing entropy)
• The H accumulate in space btwn membranes

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ETC continued

• As the e- get to the last acceptor they have
  released all the energy they were carrying from
  C-C bonds in glycolysis and Krebs
• The H can not accumulate indefinitely btwn
  membranes (high acidity)
• H flows through protein pump called ATP synthase
  toward e- and their acceptor (OXYGEN)
• This creates water and also
• Is used to generated energy to add P to ADP
• ATP is generated using oxidative phosphorylation

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