Cellular Respiration

1. Cellular Respiration Chapter 7 pgs 131-147 Food to energy

2. Autotrophs • “Self-feeders” • Plants and other organisms that make all their own organic matter from inorganic nutrients • Heterotrophs • “Other-feeders” • Humans and other animals that cannot make organic molecules from inorganic ones

3. Harvesting Chemical Energy • From photosynthesis we get carbohydrates (glucose) • Cellular respiration: Breaking down the carbohydrates (glucose) to make ATP and NADH • NADH is an electron carrier • Starts with glycolysis • Glyco = sugar • Lysis = breaking • Breaking down sugars

4. Biologists refer to plants and other autotrophs as the producers in an ecosystem • Consumers • Heterotrophs are consumers, because they eat plants or other animals • Producers Figure 6.2

5. Sunlight energy Ecosystem Photosynthesis (in chloroplasts) Carbon dioxide Glucose Oxygen Water Cellular respiration (in mitochondria) for cellular work Heat energy Figure 6.3

6. The Relationship Between Cellular Respiration and Breathing • Cellular respiration and breathing are closely related • Cellular respiration requires a cell to exchange gases with its surroundings • Breathing exchanges these gases between the blood and outside air

7. The Overall Equation for Cellular Respiration • A common fuel molecule for cellular respiration is glucose • This is the overall equation for what happens to glucose during cellular respiration Glucose Oxygen Carbon dioxide Water Energy Unnumbered Figure 6.1

8. The Role of Oxygen in Cellular Respiration • During cellular respiration, hydrogen and its bonding electrons change partners • Hydrogen and its electrons go from sugar to oxygen, forming water

9. Redox Reactions • Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions • Redox reactions for short • The loss of electrons during a redox reaction is called oxidation • The acceptance of electrons during a redox reaction is called reduction • G.E.R. L.E.O. • O.I.L. R.I.G.

10. Oxidation [Glucose loses electrons (and hydrogens)] Glucose Oxygen Carbon dioxide Water Reduction [Oxygen gains electrons (and hydrogens)] Unnumbered Figure 6.2

11. A Road Map for Cellular Respiration Cytosol Mitochondrion High-energy electrons carried mainly by NADH High-energy electrons carried by NADH Glycolysis Krebs Cycle 2 Pyruvic acid Electron Transport Glucose Figure 6.7

12. What Carries the Electrons? • NAD+(nicotinadenine dinucleotide) acts as the energy carrier • NAD+ is a coenzyme • It’s Reduced to NADH when it picks up two electrons and one hydrogen ion

13. Glycolysis • 1 six carbon glucose broken down into 2 three carbon pyruvic acid molecules • Happens out in the cytoplasm

14. 2 Pyruvic acid Glucose Figure 6.8

15. What happens next depends on whether there is oxygen present or not.

16. What happens after Glycolysis? • Chemicals can take one of two pathways • Anaerobic (no oxygen present) fermentation • Makes no ATP, but keeps the cycles going • Aerobic respiration • Makes a lot of ATP

17. EVOLUTION CONNECTION:LIFE ON AN ANAEROBIC EARTH • Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere • Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy

18. Fermentation in Human Muscle Cells • Human muscle cells can make ATP with and without oxygen • They have enough ATP to support activities such as quick sprinting for about 5 seconds • A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds • To keep running, your muscles must generate ATP by the anaerobic process of fermentation

19. Fermentation • If there is no oxygen some cells can convert pyruvic acid into other compounds and get some more NAD+ • No ATP is made, but the NAD+ can keep Glycolysis going to make a little ATP • 2 kinds of fermentation: Lactic acid fermentation and Alcoholic Fermentation

20. Lactic Acid Fermentation • Converting pyruvic acid to Lactic acid • A.K.A. milk acid • Bacteria are used to do this to get cheese, yogurt, and sour cream • Under heavy exercise you use up Oxygen faster than you can replace it • Lactic Acid builds up and the acidity causes fatigue, pain and cramps.

21. 2 ADP+ 2 Glycolysis 2 NAD 2 NAD Glucose 2 Pyruvic acid + 2 H 2 Lactic acid (a) Lactic acid fermentation Figure 6.15a

22. Alcoholic Fermentation • Yeast convert pyruvic acid into ethyl alcohol • They break a CO2 off of pyruvic acid • The 2 carbon sugar left behind forms ethyl alcohol • Basis of wine and beer industry, and bread making

23. 2 ADP+ 2 2 CO2 released 2 ATP Glycolysis 2 NAD 2 NAD 2 Ethyl alcohol Glucose 2 Pyruvic acid + 2 H (b) Alcoholic fermentation Figure 6.15b

24. Efficiency of Glycolysis • Compare the kilocalories of Glucose with the kilocalories in the ATP that is made. • The 2 ATP molecules made during glycolysis receive only 2% of the energy in glucose • Where does the rest go? • It’s still in pyruvic acid • This small amount of energy is enough for bacteria, but more complex organisms need more of glucoses energy.

25. Objectives • Define Cellular respiration • Describe the major events in glycolysis • Compare and contrast lactic acid fermentation and alcoholic fermentation • Calculate the efficiency of glycolysis

26. Stage 2: The Krebs Cycle • The Krebs cycle completes the breakdown of sugar • Another kind of breakdown

27. In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA CoA 2 1 Acetic acid 3 Pyruvic acid Acetyl-CoA (acetyl-coenzyme A) Coenzyme A CO2 Figure 6.10

28. The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2 • The cycle uses some of this energy to make ATP • The cycle also forms NADH and FADH2

29. Input Output 2 Acetic acid 1 2 CO2 ADP 3 Krebs Cycle 3 NAD 4 FAD 5 6 Figure 6.11

30. Electron Transport

31. Stage 3: Electron Transport • Electron transport releases the energy your cells need to make the most of their ATP

32. The molecules of electron transport chains are built into the inner membranes of mitochondria • The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane • These ions store potential energy

33. Protein complex Electron carrier Inner mitochondrial membrane Electron flow ATP synthase Electron transport chain Figure 6.12

34. The Versatility of Cellular Respiration • Cellular respiration can “burn” other kinds of molecules besides glucose • Diverse types of carbohydrates • Fats • Proteins

35. Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Acetyl- CoA Krebs Cycle Glycolysis Electron Transport Figure 6.13

36. Adding Up the ATP from Cellular Respiration Cytosol Mitochondrion Glycolysis 2 Acetyl- CoA Krebs Cycle 2 Pyruvic acid Electron Transport Glucose Maximum per glucose: by ATP synthase by direct synthesis by direct synthesis Figure 6.14