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Hortense Wade
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12 What is the fate of Pyruvate?

13 Stages of Cellular Respiration GLYCOLYSIS PYRUVATE OX. KREBS CYCLE ETC 2

14 The Krebs Cycle does your head suddenly hurt? 3

15 The Krebs Cycle An Overview In the presence of O 2, the pyruvate of most cells enters the Krebs cycle (citric acid cycle), in which each pyruvate is oxidized to three molecules of CO 2. 6 additional NAD + molecules are reduced to 6 NADH, and 2 FAD + (a second electron carrier) are reduced to form 2 FADH 2. 2 additional ATPs are formed as the 2 pyruvates are oxidized in the Krebs cycle. 4 The Krebs cycle occurs in the mitochondria of eukaryotic

16 Mitochondria Function Mitochondria are cell organelles. They are often called the powerhouses of the cell because they contain enzymes that help metabolize food into ATP. The ATP is generated through several oxidation reactions. All cells have different numbers of mitochondria. Cells that require a lot of energy usually have more. Structure Mitochondria have two membranes: 1)outer membrane 2)inner membrane that is folded into structures called cristae. The inner fluid of the mitochondria is called the matrix. There are hundreds of enzymes in the matrix. 5

17 Anatomy of the Mitochondria A B D C 6

18 The Krebs Cycle Oxidation of Pyruvate (transition step) Pyruvate is oxidized in the mitochondria to produce acetyl- CoA and CO 2 This reaction is a link between glycolysis and the reactions of the Krebs cycle as acetyl-coa is used by the Krebs cycle. 7

19 The Krebs Cycle Oxidation of Pyruvate (transition step) A 3 carbon molecule of pyruvate enters the mitochondrion from the cytoplasm. One carbon atom is removed via decarboxylation and hydrogen is removed using NAD+. Coenzyme A (CoA) becomes attached to the remaining 2 carbon atoms, creating Acetyl-CoA, which enters the Krebs cycle. 8

20 The Krebs Cycle Oxidation of Pyruvate (transition step) What is the word reaction for pyruvate oxidation? Pyruvate + NAD + + CoA acetyl-coa + NADH + CO 2 + H + 9

21 The Krebs Cycle most enzymes for these rxns are located in mitochondrial matrix 8 steps w/ 8 dif. enzymes oxaloacetate is recycled cycle turns twice for every glucose molecule oxidized 10

22 The Krebs Cycle Acetyl-CoA enters the cycle and then combines with oxaloacetate to make the 6-carbon compound citrate. During the eight steps of the Krebs cycle, citrate undergoes a number of reactions, releasing CO 2 and ATP in a number of steps. Citrate is eventually converted into oxaloacetate so it can be used again during the Krebs cycle. 11

23 The Krebs Cycle The Products 1. CO 2 is released as waste. 2. NADH and FADH 2 move to the next stage of cellular respiration. 3. Energy is released in the form of ATP. A glucose molecule produces two molecules of ATP. because two molecules of pyruvate are created from each molecule of glucose 12

24 The Krebs Cycle Used the diagram in the next panel to determine the products of the Krebs Cycle, both per each acetyl and glucose molecule: per acetyl molecule NADH per glucose molecule NADH FADH 2 FADH 2 ATP (subs. level) ATP CO 2 CO 2 13

25 How many oxidation reactions occur in Krebs? Where? Where does the condensation reaction occur? Where does the isomerization reaction occur? Where does substratelevel phosphorylation occur? 14

26 LAST STEP!!! Electron Transport and Chemiosmosis 10 NADH produced in Stages1-3 2 FADH 2 from Stage 3 NADH and FADH 2 transfer their electrons to the electron transport chain (ETC) 26

27 The electron transport chain (ETC) Series of proteins arranged along the inner membrane (the cristae) Increasing negativity Get a series of redox reactions Free energy released with each redox Oxygen is the final electron acceptor 27

28 ETC the finer details NADH passes 2 electrons to NADH dehydrogenase Electrons are moved along the ETC 28

29 ETC the finer details Free E that is released is used to pump H+ from the matrix intermembrane space For every pair of e-s, each protein pumps out one H+ 29

30 ETC the finer details When oxygen is reduced, it also binds 2 H+, and forms one H 2 O (inside the matrix) 30

31 Chemiosmosis = ATP formation Electrochemical (E.C.) gradient established across membrane by H+ High [H+] in intermembrane space Proton-motive force drives H+ through an ATPase complex. Free energy released. Drives phosphorylation of ADP ATP 31

32 Energy accounting One ATP formed for every H+ that moves in through ATPase For each pair of e- s, one H+ is pumped in by each of the three stationary proteins in the ECT. 32

33 3 ATP for every NADH 2 ATP for every FADH 2 FADH 2 passes its e- s to cytochrome b-c1 complex 33

34 Conversion (cashing out) 3 ATP per NADH: 3 ATP x 8 NADH = 24 ATP 2 ATP per FADH 2 2 ATP x 4 FADH 2 = 8 ATP = 32 ATP (ETC) + 4 ATP (glycol./krebs) total36 ATP 34

35 Summary of process C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy Glucose is oxidized to carbon dioxide. Oxygen is reduced to water. 36 molecules of ATP are produced. 35

3. Distinguish between aerobic and anaerobic in terms of cell respiration. Outline the general process of both.

3. Distinguish between aerobic and anaerobic in terms of cell respiration. Outline the general process of both. 3.7 Cell Respiration 1. Define cell respiration. Cell respiration is the controlled release of energy from organic molecules in cells to form ATP. 2. State the equation for the process of cell respiration.