Lect16_PS

Lect16_PS - Day 16 Figure 7.5 Energy-Producing Cells that...

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1 Capturing energy from the Sun (Phototrophy and Photosynthesis) Day 16 Figure 7.5 Energy-Producing Metabolic Pathways Cells that don’t have an outside electron acceptor (like F 3+ or O 2 ) use their own metabolites as an acceptor An OUTSIDE Acceptor is needed to get rid of NADH while benefiting from its electrons They have to give up the energy from this. Wasting reducing power (high-energy electrons) and fuel (pyruvate) You ate a candy bar. How could the sugar provide you with energy to take a run? A. The energy in the sugar was converted into ATP B. The energy in the sugar was burned up C. The energy in the sugar was released as carbon dioxide and water D. The energy in the sugar was converted to amino acids and used to construct muscles E. The energy in sugar was used to make gradients and form chemical bonds within ATP RESPIRATION Via an ETC and PMF HETEROTROPHS - burn fuel to get energy Fermentation (worse mileage) Without an acceptor, dump excess electrons on some of their own carbon Make ATP by substrate-linked phosphorylation Use ATP to make PMF Respiration (better mileage) When there’s an acceptor, use electrons to make PMF Use PMF to make ATP Burn fuel more completely Bottom Line One-minute paper • Support the statement “ Life is nothing but an electron looking for a place to rest.”
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2 Fuel X AB C D E F G Degradative pathways move in oxidative direction, generating electrons and protons (and ATP) Cells can use the ATP made oxidatively and the high-energy extracted electrons to push reductive unfavorable biosynthesis ATP ADP 2e - , 2H + 2e - , 2H + NADH NADH M Building blocks R Q P O N G (Generally energetically unfavorable) (Making fuel Y) NADPH NADPH • Why not do this for a living -- just make new fuels from existing fuels? • That is, why isn’t the pathway in the previous slide sufficient? Fuel X C D E F G Building blocks RQPO N M G (Generally energetically unfavorable) ( Making fuel Y ) ATP ADP 2e - , 2H + 2e - , 2H + NADH NADH NADPH NADPH Why might life forms have evolved ways to use additional / alternative energy sources (in addition to ‘food’)? What happens when fuel X is gone? • What happens when Fuel X is gone? – A. Life can switch to burning Fuel Y and do just fine – B. Life can switch to Fuel Y but it contains less energy, so more of it will have to be burned to do the same work – C. Life will quickly run out of fuel unless it finds another energy source. – D. Both B and C Electron Source (low energy) C D E F G Fuel R Q PO N M L Anabolic pathways build organic molecules and use up ATP, electrons (and protons) Light can provide the energy to “push” these reactions up the energetic “hill” – making new high-quality fuels ATP ADP 2e - , 2H + 2e - , 2H + NADH NADH NADPH NADPH photon photon Two types of Phototrophs • Phototrophs use pigments to capture light energy, which is then stored in chemical bonds
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This note was uploaded on 03/08/2011 for the course BIS 2A taught by Professor Grossberg during the Fall '08 term at UC Davis.

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Lect16_PS - Day 16 Figure 7.5 Energy-Producing Cells that...

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