1. Cellular Respiration

2. Harvesting Chemical Energy  So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies.  Plants and animals both use products of photosynthesis (glucose) for metabolic fuel  Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals  When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them

5. When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them  Animals use cellular respiration to transform chemical energy in food into chemical energy cells can use: ATP  These reactions proceed the same way in plants and animals.  Overall Reaction:  C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

6. How much energy is actually present in food?  1 g of sugar glucose (C6H12O6) when burned in the presence of O2 releases 3811 calories of heat energy

7. How many calories do you burn a day?

8.  Male  150 lb  5’9”  Somewhat active  Burns 3023 kcal a day or 3023 Calories or 3,023,000 calories  1 g of glucose produces 3811 calories

9. Calorie  calorie: The amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius  Calorie: food labels  1000 calories  Cells don’t burn glucose – cells gradually release energy from glucose and other food compounds  Cells release energy from glucose by performing cellular respiration

10. Cellular Respiration Overview  Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell  At this point life diverges into two forms and two pathways  Anaerobic cellular respiration (aka fermentation)  Aerobic cellular respiration

11. Cellular Respiration  Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen  C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

12. Cellular Respiration  Glycolysis  The Krebs Cycle  Electron Transport

14. Glycolysis  The process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid

15. http://upload.wikimedia.org/wiki pedia/commons/1/17/Glycolysis 2.svg

16. Glycolysis – ATP Production  2 ATP used  4 ATP produced  Net gain of 2 ATP

17. Glycolysis – NADH Production  NAD+ accepts a pair of high-energy electrons until they are transferred to other molecules

18. Anaerobic Respiration  When oxygen is not present, glycolysis is followed by a different pathway – FERMENTATION  Alcoholic fermentation (yeast)  Pyruvic acid + NADH  alcohol + CO2 + NAD+  Causes bread to rise – CO2 forms the air spaces that you see in bread  Lactic acid fermentation (muscles)  Pyruvic acid + NADH  lactic acid + NAD+

19. Substrate Level Phosphorylation

21. Glycolysis

22. Krebs Cycle

23. Citric Acid Production  Pyruvic acid enters the mitochondrion  A carbon is removed, forming CO2  Electrons are removed: NAD+  NADH  Coenzyme A joins the 2-carbon molecule, forming Acetyl-Co-A  Acetyl-Co-A then adds the 2-carbon acetyl group to a 4-carbon compound (oxaloacetate), forming Citric Acid

25. Krebs Cycle Cytoplasm Inner Mitochondrial Space

26. Acetyl Co A  Citric Acid

27. Energy Extraction  Citric acid is broken down into a 5-carbon compound, then into a 4 carbon compound  Produces  2 more molecules of CO2  NAD+  NADH  FAD+  FADH2  1 ATP

28. Electron Transport  Electrons from NADH and FADH2 are used in the electron transport chain to convert ADP to ATP

29. Electron Transport Chain  Composed of carrier proteins located in the inner membrane of the mitochondrion  High-energy electrons are passed from one carrier protein to the next  An enzyme combines these electrons with hydrogen ions and oxygen  H2O  Oxygen is the final electron acceptor of the electron transport chain  Oxygen is essential for getting rid of low-energy electrons and hydrogen ions  Low-energy electron and hydrogen ions are waste products of cellular respiration

31. Hydrogen Ion Movement  Every time 2 high-energy electrons transport down the electron transport chain, their energy is used to transport hydrogen ions (H+) across the membrane  H+ build up in the intermembrane space, making it positively charged  The other side of the membrane is negatively charge

33. ATP Production  The cell uses the build up of charge differences  As H+ escape through the ion channels, the ATP synthase (a protein enzyme) spins  Each time the ATP synthase spins, the enzyme grabs an ADP and attaches a phosphate, forming ATP  Each pair of high-energy electrons that moves down the electron transport chain provides enough energy to produce three molecules of ATP