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Ch. 9 Cellular Respiration

Ch. 9 Cellular Respiration. Harvesting chemical energy. Living is lots of work Polymerization, Growth, highly organized, and movement all require energy Energy enters Earth’s ecosystems as sunlight Harvesting of energy requires a series of metabolic steps AEROBIC CELLULAR RESPIRATION

francesca-roberts
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Ch. 9 Cellular Respiration

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  1. Ch. 9 Cellular Respiration

  2. Harvesting chemical energy • Living is lots of work • Polymerization, Growth, highly organized, and movement all require energy • Energy enters Earth’s ecosystems as sunlight • Harvesting of energy requires a series of metabolic steps • AEROBIC CELLULAR RESPIRATION • Glycolysis • Kreb’s cycle • Electron transport chain

  3. 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

  4. Exergonic reaction • Organic + oxygen  carbon + water + energy compounds dioxide C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP + heat) DG = - 686 kcal

  5. Possible pathways • Complete, aerobic cellular respiration • Complete oxidation of carbohydrates using • Glycolysis • Kreb’s cycle and • Electron transport chain REQUIRES OXYGEN • Incomplete/ partial oxidation • Gylcolysis only • Glycolysis + Lactic acid fermentation • Glycolysis + Alcoholic fermentation

  6. 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

  7. 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

  8. 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 • Kreb’s 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) andoxygen supply for (ETC)

  9. Glycolysis • Glyco = sugar, glucose • Lysis = to split or break • “sugar splitting” • Cytoplasm • ALL CELLS ! Doesn’t 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 = Kreb’s and purple = ETC

  10. 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)

  11. 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

  12. Summary of Steps 6. Enzyme adds an inorganic phosphate, sugar give e- and H+ to NAD making NADH…remember x2 7. MAKE ATP (X2) now out of debt, organic acid 8. Relocate P ( on both molecules)

  13. 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

  14. 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”

  15. 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

  16. 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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