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Lecture 6

Lecture 6. Energy. Cellular Energetics. Energy carrying molecules. ATP Synthesis. Overview of cellular energetics in a heterotroph. Heterotrophs get energy and small molecules from breakdown of large organic molecules (e. g. animals). Fig. 3-3. Photosynthesis and Respiration. Glycolysis &.

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Lecture 6

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  1. Lecture 6 Energy Cellular Energetics Energy carrying molecules ATP Synthesis

  2. Overview of cellular energetics in a heterotroph Heterotrophs get energy and small molecules from breakdown of large organic molecules (e. g. animals) Fig. 3-3

  3. Photosynthesis and Respiration Glycolysis & food Autotroph Hetrotroph Complementary processes Autotroph Next two lectures ECB Fig. 3-10

  4. Cells obey the 2nd law of thermodynamics Systems change spontaneously in direction that increases disorder (entropy) Yet cells are highly ordered structurally (organelles) and biochemically (polymers etc) Ordered cell, disordered environment Disordered cell and environment ECB 3-6

  5. Lecture 6 Energy carrying molecules in cellular energetics Electrochemical gradients ATP Redox reactions NADH, NADPH

  6. ATP stores energy in phosphoanhydride bond G0= -7.3 kcal/mole G + Drive anabolic rxs (condensation rxs) ECB Fig. 3-32

  7. Pi of ATP is transferred to other molecules forming high energy intermediates Fig. 3-34

  8. H+ e- H+ come from/go to water A A- A-H Oxidized electron carrier Reduced electron carrier Transient intermediate B-H B- B H+ e- Reduced electron carrier Oxidized electron carrier Transient intermediate Oxidation and Reduction Reactions involving movement of electron from one molecule to another Molecule gaining an electron becomes REDUCED Molecule donating an electron becomes OXIDIZED

  9. Assessing the state of oxidation/reduction CO2 -- -COOH -- -CHO -- -CH2OH -- -CH3 Acid Aldehyde Alcohol Methyl Oxidation Reduction

  10. B-H B + e- + H+ G = x AH G = y A + e- + H+ G = x + y B-H+ A B + AH NAD+ + H+ + 2e-G= -7.4 kcal/mol NADH 1/2 O2 + 2H+ + 2e- H2O G= -18.8 kcal/mol NAD+ + H2O G= -26.2 kcal/mol NADH + 1/2 O2 + H+ Coupling of redox Reactions Oxidation of one molecule coupled to reduction of another Example

  11. NAD+ NADH H+ + 2 e- Cells store reducing power as NADH and NADPH NADH and NADPH reduce other molecules

  12. Forms of stored energy in cells Electrochemical gradients Covalent bonds (ATP) Reducing power (NADH) During ATP synthesis, photosynthesis, respiration and glycolysis these forms of energy are converted from one to another Next two lectures

  13. We will go backwards: ATP syn Photosynthesis Respiration Glycolysis Big picture of metabolic pathways in heterotroph Book-Top to bottom in order and then photosynthesis Glycolysis Respiration ATP synthesis

  14. Lecture 6 Energy Cellular Energetics Energy carrying molecules ATP Synthesis

  15. H+ moving down EC gradient can do work

  16. Light (plants, bacteria) or chemical energy (plants, animals, bacteria) drives H+ out of cell H+ flows back into cell to turn bacterial flagella, drive coupled transport and synthesize ATP Chemiosmotic coupling (chemiosmotic hypothesis ) Bacterial cell

  17. ATP ADP + Pi Where in the cell is ATP made? 1. Bacterial plasma membrane 2. Mitochondrial inner membrane 3. Chloroplast thylakoid membrane bacteria mitochondria chloroplasts

  18. ATP synthase Bacterial, mito and chloro proteins are related evolutionarily ECB 14-14

  19. SynthaseATPase ECB 14-15 Rotary enzyme - can turn in either direction

  20. Experimental evidence for ATP synthesis Sealed vesicles from bacterial cell Bacteriorhodopsin pumps H+ into vesicle using light energy

  21. a b Lipid bilayer a b b a c c c b1 b1 b1 g g g       Mechanism of ATP synthesis Side view Top view • subunit rotates, • forces a and b subunits into different conformations. Conformational changes in b subunits allow it to bind ADP + Pi and make ATP

  22. ATP synthesis movies ATPSYN~1.MOV L6 movies/14.4-ATP_synthase_disco.mov See animation on ECB Interactive CD

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