Cellular Respiration

1. Cellular Respiration The Big Picture

2. The Circle of Life... • Photoautotophs: organisms that can build all the organic compounds required for life from simple ________________ materials, using _____________ in the process. • Green plants and photosynthetic microorganisms • Heterotrophs: organisms that feed on other organisms to obtain _____________ energy. • Animals, fungi, most protists and bacteria • Chemoautotrophs: organisms that can build all the organic compounds required for life from simple _______________ materials without using _____________ energy. • Some archaebacteria • Likely the first organisms on Earth

3. Glucose • With the exception of chemoautotrophs, all organisms use glucose. • Through a series of enzyme-controlled redox reactions, covalent bonds broken and rearranged into more stable configurations. • Therefore, a _______________ of energy.

4. Aerobic Cellular Respiration • glucose is oxidized to carbon dioxide and oxygen is reduced to water. • Takes about 20 reactions. • Aerobic Cellular Respiration: oxygen is used.

5. Oxidation of Glucose • Contains number of C-h bonds. • Oxygen oxidizes these bonds in two ways • C-H bonds relatively nonpolar (0.4), therefore, electron pairs are shared almost ____________. 12 hydrogen atoms break away from glucose and attach to six oxygen atoms from the six oxygen (O2) molecules  six H2O molecules.

6. Called oxidation: hydrogen atoms carry electrons away from the carbon atoms. • When H forms covalent bonds with oxygen, shared electron pairs occupy positions closer to the oxygen nuclei than they did when they were part of glucose. • H moves from EN C atoms in glucose to highly EN oxygen atooms lose potential energy. • Decrease in potential energy + increase in entropy  decrease in free energy (of the system)  overall exergonic process.

7. What about the Carbon Dioxide? • Remaining oxygen atoms must be attached to carbon atoms, forming the six carbon dioxide molecules on the product side of the overall equation. • C-O bonds are polar, therefore, oxidation reaction. • More stable configuration  release of free energy.

8. Aerobic Oxidation of Glucose • Overall: involves the movement of valence electrons from a higher free energy state in glucose to a lower free energy state in carbon dioxide and water. • Decrease in potential energy, increase in entropy.

10. Combustion of Glucose • When glucose is burned in test tube, carbon dioxide, water, and heat + light (flame) are formed. • It would not be good for the glucose in living cells to combust and give off energy as heat. • Cells have evolved methods to trap energy (about 34%). • Positions of electrons in certain molecules (like ATP) moved to higher free energy states  become readily available source of free energy to power _______________processes.

12. Glucose and Activation Energy • If reaction occurred every time glucose and oxygen came into contact, ____________________________. • All living things would be converted to ________________, ___________________, and ___________________. • Amount of ________________________ needed for combustion of glucose is relatively high. • Therefore, ______________ needed!

13. Enzymes and Respiration • Specific enzymes catalyze every step in the aerobic respriration process. • Lower _________________________ and allow reactions to occur at a rate that is __________________ with the needs of the _____________. • Available free energy transferred to a number of energy-carrier molecules, including _______.

14. Spontaneous Human Combustion? • What do you think? http://www.youtube.com/watch?v=yYyBPdxS2e8&feature=related

15. Other ways of Obtaining Energy • Obligate Aerobes: have to use aerobic respiration: obtain energy by oxidizing organic substances using oxygen. • _______________, ___________________, ______________, __________ • Obligate Anaerobes: cannot live in the presence of oxygen and obtain energy by oxidizing inorganic substances (NO2, SO4, CO2, and Fe3+ ) • Mostly bacteria • Examples: Clostridium tetani (tetanus), Clostridium perfringens (gas gangrene). • Facultative Anaerobes: obtain energy by oxidizing inorganic substances with or without oxygen • mostly bacteria • Examples: Vibriocholerae (colera) and Salmonella enteritidis (food poisoning).

16. Summary

17. Classwork/Homework Pg. 93, #1-5

18. Cellular Respiration – Introduction to the Details • There are many steps to cellular respiration, and it may seem overwhelming at times. Keep in mind the overall equation: _______________________________________________ There are three overall goals of the process • To break 6 C-C bonds in glucose to make 6 CO2 • To move hydrogen atom electrons from glucose to oxygen, forming 6 H2O. • To trap as much of the free energy released in the process as possible in the form of _____.

19. Parts of the Mitochondria

20. Cell Respiration can be divided into 4 Parts: 1) Glycolysis 2) Oxidation of Pyruvate / Transition Reaction 3) The Krebs Cycle 4) The Electron Transport Chain and Chemiosmotic Phosphorylation

21. 1) Glycolysis • 10-step process occurring in the cytoplasm. • Glucose  pyruvate • Uses substrate-level phosphorylation. • ATP is formed

22. 2) Pyruvate Oxidation 1-step process occuring in the mitochondrial matrix • Pyruvateacetyl CoA • Releases NADH

23. 3) The Krebs Cycle • Also called the tricarboxylic acid cycle, TCA or the citric acid cycle. • 8-step cylical process occurring in the mitochondrial matrix

24. 4) Electron Transport and Chemiosmosis (oxidative phosphorylation) • Multistep process occuring in the inner mitochondrial membrane.

25. Ultimate Goal for all of these steps? To ________________ energy from nutrient molecules and store it in a form that the ____________ can use for its many and varied _____________-requiring activities. The primary energy transfer is from ______________ to __________________.

26. Energy Transfer • Cell wants to capture as much of the available free energy as possible in the form of ___________. • Two energy-transfer mechanisms • Substrate-level phosphorylation • Oxidative phosphorylation

27. Substrate-Level Phosphorylation • ATP formed directly in an enzyme-catalyzed reaction. • Phosphate-containing compound transfers a phosphate group directly to ADP. ADP + Pi + energy  ATP ∆G= 31 kJ/mol • For each glucose molecule processed • 4 ATP generated this way in glycolysis • 2 ATP generated this way in the Krebs cycle

29. Oxidative Phosphorylation • APT formed indirectly • Involves a series of redox reactions, with oxygen being the final electron acceptor. • Much more complex than substrate-level phosphorylation!

30. Steps in Oxidative Phosphorylation FORMING NADH • Coenzyme Nicotinamide adenine dinucleotide, NAD+: removes 2 hydrogen atoms (2P + 2e-) from portion of original glucose molecule. • Dehydrogenaseenzyme: 2e- and 1P attach to NAD+  _______. Remaining proton dissolves into solution as _______. • NAD+  __________________ form • NADH  __________________ form

32. FORMING FADH2 1) Coenzyme FAD is reduced by two hydrogen atoms from a portion of the original glucose molecule. FAD + 2e- + 2P  FADH2.

34. So, what’s the point of forming NADH and FADH2? • All reduced coenzymes formed within first three statges (glycolysis, pyruvate oxidation, Krebs Cycle) • The reductions of NAD+ to NADH and FAD to FADH2 are energy-harvesting reactions • Act as mobile energy carriers within the cell • Will eventually transfer most of free energy to ATP during electron transport & chemiosmosis.

35. Anaerobic Respiration (no oxygen required, cytoplasm) • Glycolysis • (substrate level) Glucose  4 ATP (Net 2 ATP) 2 ATP 2 NADH 2 Pyruvate Aerobic Respiration (oxygen required, mitochondria) 2. Oxidation of Pyruvate 2 Pyruvate  2 CO2 2 NADH 2 Acetyl CoA • Krebs Cycle • (substrate level) 2 Acetyl CoA  4 CO2 2 ATP 6 NADH 2 FADH2 • Electron • Transport • Chain • (chemiosmotic) 10 NADH  32 ATP 2 FADH2 6 H2O 6 O2 Total: 36 ATP produced

36. Ideas for Assignment?