AP Biology Aim: How do we obtain energy (ATP) from our food? Do Now: Explain the diagram shown here – Fig. 9-2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy ATP

AP Biology Homework  Chapter 9 Reading Guide  Due Thursday  I suggest completing one section each night, after we have discussed it in class. Remember to read the questions before reading the text, so that your reading is focused.

AP Biology Cellular Respiration Harvesting Chemical Energy ATP

AP Biology What’s the point? The point is to make ATP ! ATP

AP Biology Harvesting stored energy  Energy is stored in organic molecules  carbohydrates, fats, proteins  Heterotrophs eat these organic molecules  food  digest organic molecules to get…  raw materials for synthesis  fuels for energy  controlled release of energy  “burning” fuels in a series of step-by-step enzyme-controlled reactions

AP Biology Harvesting stored energy  Glucose is the model  catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates) COMBUSTION = making a lot of heat energy by burning fuels in one step RESPIRATION = making ATP (& some heat) by burning fuels in many small steps CO 2 + H 2 O + ATP (+ heat) ATP glucose glucose + oxygen  energy + water + carbon dioxide respiration O2O2 O2O2 + heat enzymes ATP

AP Biology How do we harvest energy from fuels?  Digest large molecules into smaller ones  break bonds & move electrons from one molecule to another  as electrons move they “carry energy” with them  that energy is stored in another bond, released as heat or harvested to make ATP e-e- ++ e-e- +– loses e-gains e-oxidizedreduced oxidationreduction redox e-e-

AP Biology Fig. 9-UN1 becomes oxidized (loses electron) becomes reduced (gains electron)

AP Biology Fig. 9-UN2 becomes oxidized becomes reduced

AP Biology Practice If the following redox reaction occurred, which compound is oxidized? Which is reduced? C 4 H 6 O 5 + NAD +  C 4 H 4 O 5 + NADH + H +

AP Biology Practice What is the reducing agent in the following reaction? Pyruvate + NADH + H +  Lactate + NAD +

AP Biology How do we move electrons in biology?  Moving electrons in living systems  electrons cannot move alone in cells  electrons move as part of H atom  move H = move electrons p e + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H e-e-

AP Biology Coupling oxidation & reduction  REDOX reactions in respiration  release energy as breakdown organic molecules  break C-C bonds  strip off electrons from C-H bonds by removing H atoms  C 6 H 12 O 6  CO 2 = the fuel has been oxidized  electrons attracted to more electronegative atoms  in biology, the most electronegative atom?  O 2  H 2 O = oxygen has been reduced  couple REDOX reactions & use the released energy to synthesize ATP C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction O2O2

AP Biology Moving electrons in respiration  Electron carriers move electrons by shuttling H atoms around  NAD +  NADH (reduced)  FAD +2  FADH 2 (reduced) + H reduction oxidation P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H adenine ribose sugar phosphates NAD + nicotinamide Vitamin B3 niacin P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H NADH carries electrons as a reduced molecule reducing power! H like $$ in the bank

AP Biology  NADH passes the electrons to the electron transport chain  Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction  O 2 pulls electrons down the chain in an energy-yielding tumble  The energy yielded is used to regenerate ATP Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

AP Biology Fig. 9-5 Free energy, G (a) Uncontrolled reaction H2OH2O H / 2 O 2 Explosive release of heat and light energy (b) Cellular respiration Controlled release of energy for synthesis of ATP 2 H e – 2 H + 1 / 2 O 2 (from food via NADH) ATP 1 / 2 O 2 2 H + 2 e – Electron transport chain H2OH2O

AP Biology The Stages of Cellular Respiration: A Preview  Cellular respiration has three stages:  Glycolysis (breaks down glucose into two molecules of pyruvate)  The citric acid cycle (completes the breakdown of glucose)  Oxidative phosphorylation (accounts for most of the ATP synthesis) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

AP Biology Fig Substrate-level phosphorylation ATP Cytosol Glucose Pyruvate Glycolysis Electrons carried via NADH

AP Biology Fig 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

AP Biology Fig 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

AP Biology  Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration  A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

AP Biology Fig. 9-7 Enzyme ADP P Substrate Enzyme ATP + Product

AP Biology What’s the point? The point is to make ATP ! ATP

AP Biology Label the following parts of the mitochondrion:  Outer membrane  Intermembrane space  Inner membrane  Cristae  Matrix

AP Biology Source: p.166 Location – Prokaryotic Cell Location – Eukaryotic Cell Glycolysis Citric Acid Cycle Oxidative Phosphorylation