2. How Do Organisms Supply Themselves With Energy?

3. Key Questions How do organisms supply themselves with energy? How do organisms extract energy from glucose? How is the energy in glucose used to make ATP?

4. How Do Organisms Supply Themselves With Energy? All organisms need energy Ultimate source of energy on the Earth is the sun Autotrophs make their own food; –examples: plants, some bacteria Heterotrophs obtain chemical energy from other organisms –Examples?

5. Energy Currency Adenosine Triphosphate or ATP Cellular respiration produces ATP Aerobic versus anaerobic

6. Cellular Respiration

7. Steps of Cellular Respiration Step 1: glycolysis Step 2: acetyl-CoA formation Step 3: citric acid cycle Step 4: electron transport and oxidative phosphorylation

8. Cellular Respiration — Chemical Equation C 6 H 12 O 6 + 6O 2 Glucose Oxygen 6CO 2 + 6H 2 O + ATP Carbon Water Energy Dioxide

9. What Is Oxidation? Oxidizing agent or electron acceptor accepts an electron Reducing agent or electron donor donates an electron Oxidation and reduction always go hand in hand Examples of acceptors: O 2, NAD+, FAD

10. Step 1: Glycolysis Occurs in Cytoplasm Part 1: 6- carbon Glucose split into two 3-carbon molecules and are phosphorylated; uses ATP Part 2: Phosphates and electrons are removed; electrons added to NAD+ to make NADH; produces 2 ATP

11. Step 1: Glycolysis Cont. Part 3: –More electrons and phosphates are removed from the two 3-carbon molecules; –phosphates are added to ADP to make ATP

12. Glycolysis Overview Breaks glucose into 2 molecules of pyruvate, generating 2 molecules of ATP and 2 molecules of NADH  Aerobic or anaerobic?  The pyruvate enters a cell’s ______.  When compounds are reduced, they ___ electrons.  When compounds are oxidized, they ___ electrons.  Which molecules/coenzymes from Glycolysis accept electrons? ANAEROBIC MITOCHONDRIA ACCEPT DONATE NAD+

13. Step 2: Acetyl CoA Occurs in ______ aerobicOxygen needed for this reaction; aerobic Pyruvate loses a carbon and 2 oxygens in the form of CO 2 Enzymes link coenzyme A to the acetate CoA synthesizes fatty acids. MITOCHONDRIA

14. Step 3: Citric Acid Cycle Overview High energy electrons are captured in the form of NADH and FAD matrix of the mitochondriaOccurs in the matrix of the mitochondria 8With each turn of the cycle, citrate loses a total of 8 electrons to electron acceptors such as NAD+

15. Step 3: Citric Acid Cycle 3 parts3 parts –Part 1: –Part 1: 6-carbon citrate and isocitrate formation –Part 2: –Part 2: conversion of isocitrate into a 4- carbon compound –Part 3: –Part 3: production of another molecule of OAA, which starts the cycle over again

16. Citric Acid Cycle

17. What If There Is No Oxygen? fermentationAfter glycolysis, if there is no oxygen, fermentation will occur Cells must regenerate more NAD+ from NADH Yeast — form ethanol (terminal reaction produces CO 2 ) Animals — form lactic acid (ouch)

19. Biochemical Pathway Intersections Catabolism — breakdown of complex molecules such as food; produces energy, involves oxidation Anabolism — synthesis of complex molecules; uses energy Figure 6-7

20. How Do Other Food Molecules Enter Metabolism? Fat, carbohydrates and proteins enter the cellular respiration pathway at different points The most likely point is at acetyl CoA

21. Electron Transport Chain

22. Step 4: Electron Transport & Oxidative Phosphorylation The pathway of electrons from one carrier to another is called ____ ____ _____; Each electron carrier passes its electrons to the next carrier (bucket brigade) Most of the electrons to the electron transport chain are received from what cycle? A reduced carrier becomes oxidized when it gives up its electrons (forms ATP from ADP) Oxygen accepts electrons ELECTRON TRANSPORT CHAIN KREB’S

23. How Do Cells Harvest Energy? Proton gradientProton gradient — flow of electrons through the electron transport chain creates this gradient (ATP is made from this gradient) ChemiosmosisChemiosmosis — harnessing of the energy stored in the chemical gradient; some machinery in the membrane must do this process

24. Generating a Proton Gradient MitochondriaMitochondria — inner and outer membrane Intermembrane spaceIntermembrane space — space between 2 membranes MatrixMatrix — space within the inner membrane; makes up about 2/3 of the volume; ETC is embedded in this inner membrane

25. Pumping Protons pH & cytochromes assist w/ transport of electrons. Gradient is produced when…..

26. Proton complex Protons flow through these channels back into the matrix Works like a turbine Uses energy to make ATP ATP Synthase

27. Key Concepts Cellular respiration converts the chemical energy of food molecules into the chemical energy of ATP Most cells can use glycolysis to obtain energy ATP production from cellular respiration depends on oxidative phosphorylation