1. How energy is derived from food. AGRI 6203

2. Cellular Respiration Process of oxidizing food –energy released captured in ATP Two phases –glycolysis breakdown of glucose to pyruvic acid –oxidation of pyruvic acid

3. Glycolysis in eukaryotes, it occurs in the cytosol. C 6 H 12 O 6 + 2NAD + -> 2C 3 H 4 O 3 + 2NADH + 2H + The free energy stored in 2 molecules of pyruvic acid is somewhat less than that in the original glucose molecule. Some of this difference is captured in 2 molecules of ATP.

4. Glycolysis

5. Fates of Pyruvic Acid in Yeast Pyruvic acid is decarboxylated and reduced by NADH to form a molecule of carbon dioxide and one of ethanol. C3H4O3 + NADH + H+ -> CO2 + C2H5OH + NAD+ This accounts for the bubbles and alcohol in, for examples, beer and champagne. The process is called alcoholic fermentation. The process is energetically wasteful because so much of the free energy of glucose (some 95%) remains in the alcohol (a good fuel!).

6. Fate of pyruvic acid in muscles Pyruvic acid is reduced by NADH forming a molecule of lactic acid. C 3 H 4 O 3 + NADH + H+ -> C 3 H 6 O 3 + NAD + The process is called lactic acid fermentation. The process is energetically wasteful because so much free energy remains in the lactic acid molecule. (It can also be debilitating because of the drop in pH of overworked muscles.)

7. Fate of pyruvic acid in mitochondria Pyruvic acid is oxidized completely to form carbon dioxide and water. The process is called cellular respiration. Approximately 40% of the energy in the original glucose molecule is trapped in molecules of ATP.

8. Mitochondrion

9. Outer membrane –integral membrane proteins form channels Inner membrane - 5 complexes –NADH dehydrogenase –succinate dehydrogenase –cytochrome c reductase –cytochrome c oxidase –ATP synthase

10. Citric Acid Cycle Each of the 3 carbons present in pyruvate that entered the mitochondrion leaves as a molecule of CO 2 at 4 steps in the cycle, a pair of (2e-) is removed and transferred to NAD + reducing to NADH + H + at one step, a pair of electrons is removed from succinic acid and reduces FAD to FADH 2 one GTP (ATP equivalent is produced)

13. The Respiratory Chain- Function of the four integral membrane proteins NADH (FADH2) - stepwise transfer of electrons to ________ atoms to form _______. Harness the energy released by e- transfer to the pumping of protons (H+) from the matrix to intermembrane space

15. Protons are pumped a 3 complexes –NADH dehydrogenase complex –cytochrome c reductase complex –cytochrome c oxidase complex an average of three protons are pumped out at each complex as each pair of electrons passes through it –9 protons are pumped for each pair of electrons from NADH; 6 from each pair from FADH 2

16. The gradient of protons formed across the inner membrane by this process forms a miniature battery protons can flow back down this gradient, reentering the matrix, only through ATP synthase, another complex of integral protiens in the inner membrane

17. Chemiosmosis in mitochondria Energy from electrons is harnessed by –NADH dehydrogenase complex –cytochrome c reductase complex –cytochrome c oxidase complex the complexes pump protons against their gradient from the matrix into the inner membrane space a strong diffusion gradient is set up, the only exit of these protons is through ATP synthase complex

18. Sources Kimball’s Biology Pages The Biology Project Principles of Biochemisrty, Lehniger, 1982