1. CellRespiration

2. Cell Energy Chemical energy and food • one gram of glucose (C6H12O6) when burned in the presence of oxygen, releases ______ calories of heat energy • 3811 calories • calorie – amount of energy needed to raise the temperature of 1 gram of water 1 Celsius degree

3. Cell Energy Chemical energy and food • cells don’t “burn” glucose. • instead, they gradually release the energy from glucose and other food compounds. • this process begins with a pathway called? • glycolysis

4. Cell Energy Glycolysis • releases only a small amount of energy • if oxygen is present, glycolysis leads to two other pathways that release a great deal of energy • if oxygen is not present, glycolysis is followed by a different pathway

5. Cell Energy Cellular Respiration glucose Electron Transport chain Kreb cycle glycolysis lactic acid or alcohol Fermentation (in absence of oxygen)

6. Cell Energy Cellular Respiration • in the presence of oxygen, glycolysis is followed by the • Krebs cycle • Electron transport chain • these steps make up a process called cellular respiration

7. Cell Energy Cellular Respiration • the process that releases energy by breaking down food molecules in the presence of oxygen 6O2 + C6H12O6  6CO2 + 6 H2O + energy oxygen + glucose  carbon dioxide + water + energy

8. Cell Energy Energy? • if cellular respiration took place in one step, all of the energy of glucose would be released at once • most of it being in the form of light and heat • instead, the cell releases the energy a little bit at a time • these little bundles of energy are used to make ATP

9. Cell Energy Energy? • How much ATP? • A working muscle cell converts ADP into ATP at a rate of about 10 million per second

10. Cell Energy Cellular Respiration Electrons carried by NADH Pyruvic acid electron transport chain Kreb cycle glycolysis glucose (cytoplasm) (mitochondrion)

11. Cell Energy Glycolysis • process in which one molecule of ________ is broken in half

12. Cell Energy Glycolysis • process in which one molecule of glucose is broken in half • producing two molecules of _______ ____

13. Cell Energy Glycolysis • process in which one molecule of glucose is broken in half • producing two molecules of pyruvic acid • a 3-carbon compound

14. Cell Energy Glycolysis - ATP • even though glycolysis is an energy-releasing process, the cell needs to put in a little energy to get things going. • as process begins – 2 ATP molecules are used up • when complete, 4 ATP molecules have been produced • resulting in a net gain of ______

15. Cell Energy Glycolysis - ATP • even though glycolysis is an energy-releasing process, the cell needs to put in a little energy to get things going. • as process begins – 2 ATP molecules are used up • when complete, 4 ATP molecules have been produced • resulting in a net gain of 2 ATP

16. Cell Energy Glycolysis - NADH • one reaction of glycolysis removes 4 high-energy electrons and passes them on to an electron carrier (similar to photosynthesis) • electron carrier – NAD+ • this carrier holds the electrons until they can be transferred to other molecules

17. Cell Energy Glycolysis - Energy • although the energy yield from glycolysis is small, the process is so fast that cells can produce thousands of ATP molecules in just a few milliseconds • problem – in a few seconds, all the NAD+ molecules are filled with electrons. • result – ATP production stops

18. Cell Energy Glycolysis glucose pyruvic acid To the electron transport chain

19. Cell Energy Fermentation • releases energy from food molecules in the absence of oxygen • anaerobic process – does not require oxygen • two main types of fermentation • Alcoholic • Lactic acid

20. Cell Energy Alcoholic Fermentation • occurs in yeast and a few other microorganisms • forms ethyl alcohol and carbon dioxide as wastes pyruvic acid + NADH  alcohol + CO2 + NAD+

21. Cell Energy Lactic Acid Fermentation pyruvic acid + NADH  lactic acid + NAD+ • occurs in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues. • build up of lactic acid in muscles is what causes painful, burning sensation and eventually muscle fatigue

22. Cell Energy Glycolosis • at the end of this first step of cellular respiration 90 percent of the chemical energy that was available in glucose is still unused – locked in the high-energy electrons of pyruvic acid. • oxygen • powerful electron acceptor • required for rest of cellular respiration • this makes it an aerobic process

23. Cell Energy The Krebs Cycle • general summary of reactions • pyruvic acid is broken down into carbon dioxide in a series of energy extracting reactions • two main reactions • citric acid production • energy extraction

24. Cell Energy The Krebs Cycle • Citric acid production • pyruvic acid enters the mitochondria • one C bonds with O to become CO2 and is released • 2 remaining C’s used to form acetyl-CoA • acetyl-CoA is added to a 4-C molecule to form citric acid

25. Cell Energy The Krebs Cycle Citric acid production

26. Cell Energy The Krebs Cycle • energy extraction • in stages, the 6-C citric acid is converted to a 4-C molecule • during this process the following occurs • 5 pairs of high-energy electrons are captured by 5 carrier molecules (NADH & FADH2) • CO2 and ATP produced

27. Cell Energy The Krebs Cycle Energy extraction

28. Cell Energy Electron Transport Chain • general summary of reaction • electron transport chain uses high-energy electrons from Krebs cycle to convert ADP into ATP • it is divided into 3 steps • electron transport • hydrogen ion movement • ATP production

29. Cell Energy Electron Transport • electron transport • high-energy electrons from NADH and FADH2 are passed along the chain • oxygen serves as the final electron acceptor in the chain • hydrogen ion movement • energy from 2 high-energy electrons is used to transport hydrogen ions (H+) • this eventually results in a slight positive charge inside the membrane and a slight negative charge outside the membrane

30. Cell Energy Electron Transport • ATP production • inner membrane contains protein spheres called ATP synthase • charge difference between inside and outside causes H+ to escape through these proteins • as H+ escapes it causes part of protein to spin • this spinning creates ATP from ADP • on average each pair of high-energy electrons produces 3 ATP molecules

31. Cell Energy Electron Transport

32. Cell Energy How much energy from glucose? • glycolysis 2 ATP net • fermentation 0 ATP (when no oxygen present) Total 2 ATP

33. Cell Energy How much energy from glucose? • glycolysis 2 ATP net • Krebs cycle and Electron transport chain 34 ATP (in presence of oxygen) TOTAL 36 ATP • This amount of ATP is roughly 38% of total energy in a glucose molecule. • The remaining 62% is released as heat.

34. Cell Energy Photosynthesis and Cellular Respiration • turn to page 232, Figure 9-10 • what is similar about these reactions? • the reactants of one reaction are the products of the other