Energy Supply and Cellular Respiration: How Organisms Extract and Utilize Energy

1. Chapter 6 How Do Organisms Supply Themselves With Energy?

2. 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?

3. 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?

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

5. Cellular Respiration

6. Steps of Cellular Respiration • Step 1: glycolysis • Step 2: acetyl-CoA formation • Step 3: citric acid cycle • Step 4: electron transport and oxidative phosphorylation • Overall equation: glucose + oxygen carbon dioxide + water + ATP

7. Cellular Respiration — Chemical Formula • C6H12O6 + 6O2 Glucose Oxygen • 6CO2 +6H2O + ATP Carbon Water Energy Dioxide

8. What Is Oxidation? • Oxidizing agent or electron acceptoraccepts an electron • Reducing agent or electron donor donates an electron • Oxidation and reduction always go hand in hand • Examples of acceptors: O2, NAD+, FAD

9. Step 1: GlycolysisOccurs in Cytoplasm • Part 1: 6 carbons are split into 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

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

11. 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?

12. Step 2: Acetyl CoAOccurs in ______ • Oxygen needed for this reaction; aerobic • Pyruvate loses a carbon and 2 oxygens in the form of CO2 • Enzymes link coenzyme A to the acetate • CoA synthesizes fatty acids.

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

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

15. Citric Acid Cycle The acetyl group is oxidized and energy is captured as ___, ___, & ____.

16. What If There Is No Oxygen? • After glycolysis, if there is no oxygen, fermentation will occur • Cells must regenerate more NAD+ from NADH • Yeast — form ethanol (terminal reaction produces CO2 ) • Animals — form lactic acid (ouch)

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

18. 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

19. Electron Transport Chain

20. 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

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

22. Generating a Proton Gradient • Mitochondria — inner and outer membrane • Intermembrane space — space between 2 membranes • Matrix — space w/n the inner membrane; makes up about 2/3 of the volume; ETC is embedded in this inner membrane

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

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

25. Fragments of Inner Membrane

26. Think About This One! • Why might you lose weight (a lot of weight) if your mitochondria suddenly lost the ability to couple electron transport to the production of ATP?

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