2.  Organisms must take in energy from outside sources.  Energy is incorporated into organic molecules such as glucose in the process of photosynthesis.  Glucose is then broken down in cellular respiration. The energy is stored in ATP.

3. Fig. 9-2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Cellular respiration in mitochondria Organic molecules +O2+O2 ATP powers most cellular work Heat energy ATP The Flow of Energy from Sunlight to ATP

4.  Energy in food is stored as carbohydrates (such as glucose), proteins & fats. Before that energy can be used by cells, it must be released and transferred to ATP.

5.  Aerobic Cellular Respiration: the process that releases energy by breaking down food (glucose) molecules in the presence of oxygen.  Formula: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O +~ 36 ATP  Fermentation: the partial breakdown of glucose without oxygen. It only releases a small amount of ATP.  Glycolysis: the first step of breaking down glucose—it splits glucose (6C) into 2 pyruvic acid molecules (3C each)

6.  The transfer of electrons during chemical reactions releases energy stored in organic compounds such as glucose.  Oxidation-reduction reactions are those that involve the transfer of an electron from one substance to another.

7.  Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions In oxidation, one substance loses electrons, or is oxidized  In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Na will easily lose its outer electron to Cl. Why? In this reaction, which atom is oxidized? Which is reduced?

8. becomes oxidized becomes reduced In cellular respiration, glucose is broken down and loses its electrons in the process. The glucose becomes oxidized and the Oxygen is reduced. Redox Reactions of Cellular Respiration

9.  In cellular respiration, glucose is broken down in a series of steps.  As it is broken down, electrons from glucose are transferred to NAD+, a coenzyme  When it receives the electrons, it is converted to NADH. NADH represents stored energy that can be used to make ATP

10.  NADH passes the electrons to the electron transport chain, a series of proteins embedded in the inner membrane of the mitochondria.  The electrons (and the energy they carry) are transferred from one protein to the next in a series of steps.

11. Free energy, G (a) Uncontrolled reaction H2OH2O H 2 + 1 / 2 O 2 Explosive release of heat and light energy (b) Cellular respiration Controlled release of energy for synthesis of ATP 2 H + + 2 e – 2 H + 1 / 2 O 2 (from food via NADH) ATP 1 / 2 O 2 2 H + 2 e – Electron transport chain H2OH2O Energy is released a little at a time, rather than one big explosive reaction:

12.  Cellular respiration has three stages:  Glycolysis (breaks down glucose into two molecules of pyruvate)  The C itric Acid cycle/Kreb’s Cycle (completes the breakdown of glucose)  Electron Transport Chain and Oxidative phosphorylation (accounts for most of the ATP synthesis) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

13. Substrate-level phosphorylation ATP Cytosol Glucose Pyruvate Glycolysis Electrons carried via NADH An Overview of Cellular Respiration–Part 1

14. Mitochondrion Substrate-level phosphorylation ATP Cytosol Glucose Pyruvate Glycolysis Electrons carried via NADH Substrate-level phosphorylation ATP Electrons carried via NADH and FADH 2 Citric acid cycle An Overview of Cellular Respiration—Part 2

15. Mitochondrion Substrate-level phosphorylation ATP Cytosol Glucose Pyruvate Glycolysis Electrons carried via NADH Substrate-level phosphorylation ATP Electrons carried via NADH and FADH 2 Oxidative phosphorylation ATP Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis An Overview of Cellular Respiration—Part 3

16.  Substrate-level phosphorylation:  Phosphate is added to ADP to make ATP by using an enzyme:  Oxidative phosphorylation:  Phosphate is added to ADP to make ATP by ATP Synthase—a protein embedded in the mitochondria membrane (requires O 2 ) WAY MORE EFFICIENT!! PRODUCES LOTS MORE ATP!

17.  “Glyco”=sugar; “lysis”=to split  In this first series of reactions, glucose (C6) is split into two molecules of pyruvic acid (C3).  This occurs in the cytoplasm of cells and does not require oxygen.  This releases only 2 ATP molecules, not enough for most living organisms.  http://highered.mcgraw- hill.com/sites/0072507470/student_view0/cha pter25/animation__how_glycolysis_works.htm l http://highered.mcgraw- hill.com/sites/0072507470/student_view0/cha pter25/animation__how_glycolysis_works.htm l

18. Energy investment phase Glucose 2 ADP + 2 P 2 ATPused formed 4 ATP Energy payoff phase 4 ADP + 4 P 2 NAD + + 4 e – + 4 H + 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O Glucose Net 4 ATP formed – 2 ATP used2 ATP 2 NAD + + 4 e – + 4 H + 2 NADH + 2 H + Glycolysis

19.  The Citric Acid Cycle (also called the Kreb’s Cycle) completes the breakdown of pyruvate and the release of energy from glucose.  It occurs in the matrix of the mitochondria.

20.  In the presence of oxygen, pyruvate enters the mitochondria.  Before the pyruvate can enter the Citric Acid Cycle, however, it must be converted to Acetyl Co-A.  Some energy is released and NADH is formed.

21. CYTOSOL MITOCHONDRION NAD + NADH+ H + 2 1 3 Pyruvate Transport protein CO 2 Coenzyme A Acetyl CoA Converting Pyruvate to Acetyl CoA:

22.  The Acetyl Co-A enters the Citric Acid Cycle in the matrix of the mitochondria.  The Citric Acid cycle breaks down the Acetyl Co-A in a series of steps, releasing CO 2  It produces 1 ATP, 3 NADH, and 1 FADH 2 per turn.

23. The Citric Acid cycle (also called the Krebs Cycle) has eight steps, each catalyzed by a specific enzyme The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate (Citric Acid). The next seven steps decompose the citrate (Citric Acid) back to oxaloacetate, making the process a cycle The Citric Acid Cycle Oxaloacetate + Acetyl CoACitric Acid

24. Acetyl CoA CoA—SH Citrate H2OH2O Isocitrate NAD + NADH + H + CO2CO2  -Keto- glutarate CoA—SH CO2CO2 NAD + NADH + H + Succinyl CoA CoA—SH P i GTP GDP ADP ATP Succinate FAD FADH 2 Fumarate Citric acid cycle H2OH2O Malate Oxaloacetate NADH +H + NAD + 1 2 3 4 5 6 7 8 The Citric Acid Cycle:

25.  http://highered.mcgraw- hill.com/sites/0072507470/student_view0/cha pter25/animation__how_the_krebs_cycle_wor ks__quiz_1_.html http://highered.mcgraw- hill.com/sites/0072507470/student_view0/cha pter25/animation__how_the_krebs_cycle_wor ks__quiz_1_.html

26. Each Citric Acid Cycle only produces 1 ATP molecule. The rest of the energy from pyruvate is in the NADH and FADH 2. The NADH and FADH 2 produced by the Citric Acid cycle relay electrons extracted from food to the electron transport chain.

27.  The electron transport chain is in the cristae of the mitochondrion  Most of the chain’s components are proteins, which exist in multiprotein complexes  The carriers alternate reduced and oxidized states as they accept and donate electrons  Electrons drop in free energy as they go down the chain and are finally passed to O 2, forming H 2 O Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Oxygen is the final electron acceptor.

28. NADH NAD + 2 FADH 2 2 FAD Multiprotein complexes FAD FeS FMN FeS Q  Cyt b   Cyt c 1 Cyt c Cyt a Cyt a 3 IVIV Free energy (G) relative to O 2 (kcal/mol) 50 40 30 20 10 2 (from NADH or FADH 2 ) 0 2 H + + 1 / 2 O2O2 H2OH2O e–e– e–e– e–e– The Electron Transport Chain

29.  Electrons are transferred from NADH or FADH 2 to the electron transport chain  Electrons are passed through a number of proteins to O 2  The chain’s function is to break the large free- energy drop from food to O 2 into smaller steps that release energy in manageable amounts

30.  http://www.youtube.com/watch?v=xbJ0nbzt 5Kw http://www.youtube.com/watch?v=xbJ0nbzt 5Kw

31.  Electron transfer in the electron transport chain causes proteins to pump H + from the mitochondrial matrix to the intermembrane space  H + then moves back across the membrane, passing through channels in ATP synthase  Animation: http://sp.uconn.edu/~terry/images/anim/ETS. html http://sp.uconn.edu/~terry/images/anim/ETS. html

32.  ATP synthase uses the exergonic flow of H + to drive phosphorylation of ATP  This is an example of chemiosmosis, the use of energy in a H + gradient to drive cellular work

33. INTERMEMBRANE SPACE Rotor H+H+ Stator Internal rod Cata- lytic knob ADP + P ATP i MITOCHONDRIAL MATRIX ATP Synthase

34. Protein complex of electron carriers H+H+ H+H+ H+H+ Cyt c Q    VV FADH 2 FAD NAD + NADH (carrying electrons from food) Electron transport chain 2 H + + 1 / 2 O 2 H2OH2O ADP + P i Chemiosmosis Oxidative phosphorylation H+H+ H+H+ ATP synthase ATP 21 Chemiosmosis couples the electron transport chain to ATP synthesis

35.  During cellular respiration, most energy flows in this sequence: glucose  NADH  electron transport chain  proton-motive force  ATP  About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP + 6 O 2 6CO 2 + 6H 2 O + 38 ATP

36. Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA Glycolysis Glucose 2 Pyruvate 2 NADH 6 NADH2 FADH 2 2 NADH CYTOSOL Electron shuttles span membrane or MITOCHONDRION ATP Yield per molecule of glucose at each stage of cellular respiration: