1. 1 Central Metabolism: Funneling all nutrients into central pathways Many other molecules besides glucose can serve as a source of carbon.

2. 2 Central Metabolism: A source of building blocks for biosynthesis BUT, these molecules can’t be broken down to CO 2 for energy AND used for biosynthesis

3. 3 Other ways to make ATP Photosynthesis: light driven ATP synthesis. Anaerobic respiration: organic compounds oxidized, electrons passed down e- transport chain to some molecule other than oxygen (e.g. NO 3, SO 4 ). Inorganic molecules can be oxidized with ATP synthesis by e- transport and chemiosmosis. Fermentation: common anaerobic pathway used by many medically important bacteria.

4. 4 What’s Fermentation for? Glucose can be oxidized to pyruvic acid with the synthesis of 2ATPs. This alone is enough energy to live on. It depends on the oxidation of NADH to NAD so that NAD is available to accept electrons during the oxidation of glucose.

5. 5 Why fermentation-2

6. 6 Fermentation: “life without air” Without O 2 as an e- acceptor, NADH cannot be re-oxidized to NAD. Even though aerobic metabolism can produce ~36 ATP from 1 glucose, the 2 ATP from glycolysis is enough. But glycolysis requires that NAD be reduced to NADH; what happens when ALL the NAD becomes NADH with no O 2 to accept the H? Pyruvic acid is reduced, and the product thrown away; NAD restored, glycolysis can be repeated, more ATP made. A variety of ways of solving this problem exist; many types of molecules can be produced from fermentation.

7. 7 Lessons from Fermentation Fermentation is inefficient. If C 6 H 12 O 6 has lots of energy-rich H’s, so does C 3 H 5 O 3 (lactic acid); the product cannot be further metabolized and is thrown away! Only a couple of ATPs are made. Fermentation is quick. Even though few ATPs are made, they are made quickly. Fermentation is wasteful. Large amounts of substrate (e.g. sugar) is used, making large amounts of product (e.g. lactic acid, ethanol, etc.)

8. 8 Anaerobic respiration Not the same as fermentation –Respiration involves the electron transport chain and ATP synthesis by chemiosmosis. –Most general biologists are very confused. Anaerobic means without oxygen Anaerobic respiration: organic (or inorganic) molecule is oxidized, the removed electrons are sent down the electron transport chain, and something OTHER than oxygen is the electron acceptor. –Carried out by anaerobic bacteria, but some aerobes can reduce forms of N this way.

9. 9 Anaerobic respiration In this example, nitrate is reduced to nitrite. Other examples: sulfate reduced to elemental sulfur (S) or S to sulfide (H 2 S).

10. 10 Bacteria and the fragility of existence Bacteria use ATP or the proton motive force to: –Move –Synthesis proteins (lots of them) –Transport molecules into the cell –Synthesize cell materials –Homeostasis Bacteria do not store ATP –Calculations: E. coli has enough ATP to last a few seconds –Thus, cells must keep on making it.

11. 11 Essay score Multiple choice score Final curved, corrected, or adjusted score. Correct answers. What you put if different.