1. Photosynthesis and cellular respiration provide energy for life Energy in sunlight is used in photosynthesis to make glucose from CO 2 and H 2 O with release of O 2 Other organisms use the O 2 and energy in sugar and release CO 2 and H 2 O (cellular respiration) Together, these two processes are responsible for the majority of life on Earth Copyright © 2009 Pearson Education, Inc.

2. Sunlight energyا ECOSYSTEM Photosynthesis in chloroplasts Glucose Cellular respiration in mitochondria H2OH2O CO 2 O2O2  (for cellular work ) ATP Heat energy The connection between photosynthesis and cellular respiration

3. INTRODUCTION TO CELLULAR RESPIRATION Copyright © 2009 Pearson Education, Inc.

4. Cellular respiration banks energy in ATP molecules Cellular respiration is an exergonic process that transfers energy stored in glucose bonds to ATP –Cellular respiration produces 38 ATP molecules from each glucose molecule –Other foods (protein and lipid) can be used as a source of energy as well Copyright © 2009 Pearson Education, Inc.

5. C 6 H 12 O 6 + 6O2O2 Glucose Oxygen 6 CO 2 Carbon dioxide + 6 H2OH2O Water + ATPs Energy Summary equation for cellular respiration

6. How do cells extract energy in chemical bonds in organic molecules The energy necessary for life is contained in the arrangement of electrons in chemical bonds in organic molecules Copyright © 2009 Pearson Education, Inc.  When the carbon-hydrogen bonds of glucose are broken, electrons are transferred to oxygen –Oxygen has a strong tendency to attract electrons

7. How do cells extract energy in chemical bonds in organic molecules A cellular respiration equation is helpful to show the changes in hydrogen atom distribution –Glucose loses its hydrogen atoms and is ultimately converted to CO 2 –At the same time, O 2 gains hydrogen atoms and is converted to H 2 O –Loss of electrons is called oxidation –Gain of electrons is called reduction Copyright © 2009 Pearson Education, Inc.

8. C 6 H 12 O 6 + 6 O 2 Glucose Loss of hydrogen atoms (oxidation ) 6 CO 2 + 6 H 2 O + Energy Gain of hydrogen atoms (reduction ) (38 ATP) Rearrangement of hydrogen atoms (with their electrons) Reduction &Oxidation) in the redox (Reduction &Oxidation) reactions of cellular respiration Reduction & Oxidation) Redox (Reduction & Oxidation) reactions

9. How do cells extract energy in chemical bonds in organic molecules Enzymes are necessary to oxidize glucose and other foods –The enzyme that removes hydrogen from an organic molecule is called dehydrogenase –Dehydrogenase requires a coenzyme called NAD + (nicotinamide adenine dinucleotide) to shuttle electrons –NAD + can become reduced when it accepts electrons and oxidized when it gives them up Copyright © 2009 Pearson Education, Inc.

10. 2 H + + 2 e – Oxidation Dehydrogenase Reduction NAD + + 2 H NADH + H+H+ (carries 2 electrons) ) pair of redox reactions, occurring simultaneously

11. Cells tap energy from electrons “falling” from organic fuels to oxygen The transfer of electrons to NAD + results in the formation of NADH, the reduced form of NAD + –In this situation, NAD + is called an electron acceptor, but it eventually becomes oxidized (loses an electron) and is then called an electron donor Copyright © 2009 Pearson Education, Inc.

12. Cells tap energy from electrons “falling” from organic fuels to oxygen There are other electron “carrier” molecules that function like NAD + –They form a staircase where the electrons pass from one to the next down the staircase –These electron carriers collectively are called the electron transport chain, and as electrons are transported down the chain, ATP is generated Copyright © 2009 Pearson Education, Inc.

13. ATP NAD + NADH H+H+ H+H+ 2e – Electron transport chain Controlled release of energy for synthesis of ATP + O2O2 H2OH2O 1212 In cellular respiration, electrons fall down an energy staircase and finally reduce O2

14. Stages of Aerobic Cellular Respiration and Fermentation Copyright © 2009 Pearson Education, Inc.

15. What are the Stages of Cellular Respiration? 1. Glycolysis occurs in the Cytoplasm 2. The Krebs Cycle or citric acid cycle occurs in the mitochondria matrix 3. Oxidation phosphorylation or The Electron Transport Chain occurs in the mitochondria inner membrane

16. Overview: Cellular respiration Glycolysis Stage 1: Glycolysis –Glycolysis begins respiration by breaking glucose, a six-carbon molecule, into two molecules of a three-carbon compound called pyruvate –This stage occurs in the cytoplasm Copyright © 2009 Pearson Education, Inc. C-C-C-C-C-CC-C-C Glycolysis In Cytoplasm Glucose Pyruvate

17. Glucose NAD + + 2 2 ADP NADH2 P2 2 ATP 2 + H+H+ 2 Pyruvate An overview of glycolysis  In glycolysis, a single molecule of glucose is enzymatically cut in half through a series of steps to produce two molecules of pyruvate –In the process, two molecules of NAD + are reduced to two molecules of NADH –At the same time, two molecules of ATP are produced by substrate-level phosphorylation Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

18. Stage 2: The citric acid cycle (Krebs Cycle) A Little Krebs Cycle History Discovered by Hans Krebs in 1937Discovered by Hans Krebs in 1937 He received the Nobel Prize in physiology or medicine in 1953 for his discoveryHe received the Nobel Prize in physiology or medicine in 1953 for his discovery

19. Overview Stage 2: The citric acid cycle Stage 2: The citric acid cycle –The citric acid cycle breaks down pyruvate into carbon dioxide and supplies the third stage Oxidative phosphorylation with electrons –This The citric acid cycle stage occurs in the mitochondria matrix –For each Glucose molecule, the Krebs Cycle produces 6NADH, 2FADH 2, 4CO 2, and 2ATP Citric Acid Cycle Pyruvate Electrons Mitochondria CO 2

20. Overview: Cellular respiration occurs in three main stages Stage 3: Oxidative phosphorylation –At this stage, electrons are shuttled through the electron transport chain –As a result, ATP is generated through oxidative phosphorylation –(oxidation of NADH to NAD and phosphorylation of ADP to ATP) Occurs Across Inner Mitochondrial membrane –This stage Occurs Across Inner Mitochondrial membrane Pyruvate Citric Acid Cycle Electrons CO 2 Electron Transport Chain O2O2 H2OH2O ATP Oxidative Phosphorylation Mitochondria Chemiosmosis

21. ATP NAD + NADH H+H+ H+H+ 2e – Electron transport chain Controlled release of energy for synthesis of ATP + O2O2 H2OH2O 1212 In cellular respiration, electrons fall down an energy staircase and finally reduce O2

22. Mitochondrion CO 2 NADH ATP High-energy electrons carried by NADH NADH C ITRIC A CID C YCLE G LYCOLYSIS Pyruvate Glucose and FADH 2 Substrate-level phosphorylation Substrate-level phosphorylation O XIDATIVE P HOSPHORYLATION (Electron Transport and Chemiosmosis) Oxidative phosphorylation ATP Cytoplasm Inner mitochondrial Membrane An overview of cellular respiration

23. Fermentation Fermentation “NO Oxygen”(called anaerobic).Occurs in cytosol when “NO Oxygen” is present (called anaerobic). Fermentation enables cells to produce ATP without oxygen. Net energy gain only 2 ATP per glucose glycolysisfermentationRemember: glycolysis is part of fermentation. Two Types:Two Types: 1.Alcohol Fermentation 2. Lactic Acid Fermentation

24. Fermentation Anaerobic process –no ETC Net energy gain only 2 ATP per glucose –produced by substrate-level phosphorylation during glycolysis NAD + –produced by transferring H from NADH to organic compound from nutrient

25. Fermentation enables cells to produce ATP without oxygen Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation NADH is oxidized to NAD + when pyruvate is reduced to lactate The baking industry have used alcohol fermentation for thousands of years –Yeasts are single-celled fungi that ferment under anaerobic conditions –They convert pyruvate to CO 2 and ethanol while oxidizing NADH back to NAD + Copyright © 2009 Pearson Education, Inc.

26. Glucose NADH NAD + 2 2 NADH 2 NAD + 2 2 ADP P ATP 2 2 Pyruvate 2 Lactate GLYCOLYSIS Lactic acid fermentation  2

27. 2 ADP P ATP 2 GLYCOLYSIS NADH NAD + 2 2 NADH 2 NAD + 2 2 Pyruvate2 بايروفيت 2 Ethanol Alcohol fermentation Glucose CO 2 2 Released CO 2  2