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EXAM REVIEW EXAM I CLASS AVERAGE = 59.1 EXAM II CLASS AVERAGE= 71.7 The class increased the average by 12.6 points!! 21/41 (51%) students received a C or better 31/41 (76%) students received a D or better EXAM II Grade Distribution NUMBER OF STUDENTS 12 10 8 6 4 2 0 A B C GRADE D F Trouble Spots • • • • • • • • Question 2 Question 5 Question 7 Questions 30-33 Question 35 Question 40 Question 44 Questions 46-49 NEXT EXAM APRIL 12, 2011 COVERS WEEKS 7, 8, 9 and 10 WEEK 8 Glycolysis-Review (anaerobic) Fermentation (anaerobic) Cellular Respiration (aerobic) The Metabolic Pool Pages 134-147 Production of Energy from Food = Cellular Respiration I. Anaerobic (no oxygen used) a. Glycolysis- Net gain of 2 ATP b. Fermentation – No ATP gained II. Aerobic (continuing from Glycolysis w/ Oxygen) b. The preparatory reaction c. Citric Acid Cycle d. Electron Transport Chain and chemiosmosis If OXYGEN is Present: Pyruvate enters the mitochondria Cell Respiration If OXYGEN is not Present: Pyruvate enters an anaerobic process called fermentation Glycolysis Review • Anaerobic Process • No oxygen required • Occurs outside the mitochondria • Produces 2, 3-C Pyruvate molecules OXIDATION REDUCTION LOSS OF ELECTRONS GAIN OF ELECTRONS RED-OX REACTION Page 134 L E O the lion says GERRRR OXIDATION REDUCTION LOSS OF ELECTRONS GAIN OF ELECTRONS H lost from glucose H transferred to water The 4 Steps of Cellular Respiration GLUCOSE 2 pyruvate molecules Oxidation NADH Net gain of 2 ATP 1. GLYCOLYSIS-does not require O2 -Is therefore, anaerobic -Occurs OUTSIDE of the mitochondria 2. PREPARATORY REACTION PYRUVATE Two C Acetyl Group +CO2 This occurs 2X b/c 2 pyruvates are -Requires O2 produced in glycolysis -Is therefore, aerobic -Takes place INSIDE of the mitochondria (matrix) 3. CITRIC ACID CYCLE -Requires O2 -Is therefore, aerobic -Takes place INSIDE of the mitochondria (matrix) 4. NADH +FADH2 give up e- to the “chain” ELECTRON TRANSPORT CHAIN (series of proteins in mito. cristae) -Requires O2 e- are transported from high to low -Is therefore, aerobic -Takes place INSIDE of the mitochondria (cristae) energy states More oxidation NADH +FADH2 More CO2 is released This cycle occurs 2X b/c 2 Acetyl groups Were produced in the PREP Rxn. 2 ATP gained (1 per cycle) 32 ATP are produced via “chemiosmosis” STEP/PHASE 1. Glycolysis Occurs within the cytoplasm outside of the mitochondria Is the breakdown of GLUCOSE into 2 pyruvate molecules 2-ATP molecules are used to “jump-start” the reactions in glycolysis Page 138, section 8.2 Glycolysis Begins as glucose diffuses into the cytoplasm of the cell from the blood stream 2 ATP are used to add 2 phosphate groups to the glucose, thereby energizing the Glucose molecule The energized glucose molecule splits apart and creates 2 PGAL (phosphoglyceraldehyde) molecules Glycolysis ATP is used to add a phosphate group to the ends of the glucose molecule This addition of phosphates energizes the glucose molecule The energized glucose splits into 2 G3P molecules (3-carbon molecules) Glycolysis G3P gets oxidized as NAD+ gets reduced 2 BPG molecules are produced via the addition of phosphate onto the ends of G3P Glycolysis phosphoenol pyruvate(PEP) ATP is created as ADP is phosphorylated Note the loss of the phosphate group from the 3-C molecules as ATP is created Glycolysis Metabolic Pathway NET GAIN OF 2 ATP Fermentation • • • • • Break down of glucose in the absence of O2 Anaerobic Occurs after glycolysis Occurs if there is a continued absence of oxygen Pyruvate is turned into “waste product” – No more energy is produced • What organisms do fermentation? – Bacteria – Yeast – Animals Two types of Fermentation I. Lactic Acid Fermentation (fungi, bacteria, muscles) Pyruvate Lactic Acid (C3H6O3) + NAD+ II. Alcohol Fermentation (yeasts) Pyruvate Ethanol (C2H5OH) + Carbon Dioxide (CO2) + NAD+ Lactic Acid Fermentation • Pyruvate is reduced by NADH to lactate (pyruvate receives electrons from NADH NAD+) • WHY do Fermentation? – NAD+ is generated which can be “recycled” for reuse in earlier reactions – NAD+ can be reduced to NADH and then NADH can reduce pyruvate once again – ATP is continuously produced even w/o the presence of oxygen, albeit very little ATP is generated (only 2 ATP!) Fig. 8.5 pg 138 Advantages/Disadvantages of Fermentation • Anaerobic bacteria and yeast can be used to produce food products – Ex. yeast fermentation yield CO2 bread rises – Ex. yeast fermentation yields alcohol produce wine and beer (fermentation of fruit= wine, fermentation of grain = beer) – Ex. bacteria convert alcohol to acid (vinegar) – Production of yogurt, cheese, sour cream via bacterial fermentation See page 139, Chapter 8 Advantages/Disadvantages of Fermentation • Lactic acid fermentation is critical for certain animals and tissues • Animals use lactic acid for rapid bursts of energy • Lactic acid fermentation provides continued production of ATP in absence of oxygen via the cycling of NAD+ • Lactic acid and alcohol are toxic to cells, bacteria and yeasts • Lactic acid build up in humans causes change in pH in blood • Continued lack of O2 = oxygen debt (amount of oxygen needed to rid body of lactic acid), heavy breathing after exercise recovery Glycolysis 2 ATP 2 NADH With OXYGEN 2 Pyruvate Without OXYGEN a. The preparatory reaction b. Citric Acid Cycle (2 ATP) c. Electron Transport Chain and chemiosmosis Lactic Acid Fermentation OR Alcohol Fermentation TOTAL of 36-38 ATP produced TOTAL of 2 ATP Produced Cellular Respiration (Oxygen present) After glycolysis occurs in the cytoplasm: a. Prep Reaction (mitochondrial matrix) b. Citric Acid Cycle/Krebs Cycle (mitochondrial matrix) c. Electron Transport Chain (cristae) Cellular Respiration C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY (Required!) HIGH ENERGY LOW ENERGY LOW ENERGY ENERGY RELEASED Product of Glucose Breakdown/ Bonds Broken Inside the Mitochondria Majority of the ATP produced from the breakdown of Glucose occurs in the Mitochondria ! a. The Preparatory Reaction • Occurs after glycolysis and before the Citric Acid Cycle/Krebs Cycle • The prep reaction converts the two 3-C pyruvate to two 2-C acetyl group and CO2 is released • This is done with the help of Coenzyme A THE PREP REACTION Pg. 140 Chpt. 8 Glycolysis Electrons are removed from PYRUVATE by NAD+ = Pyruvate is OXIDIZED One prep reaction per pyruvate = 2 acetyl-CoA Coenzyme A is a MOLECULE A molecule of coenzyme A carrying an acetyl group is referred to as acetyl-CoA Coenzyme A oxidizes PYRUVATE Prep Reaction 1. CO2 is released (to blood) as Pyruvate is carried into the mitochondria 2. NAD+ oxidizes Pyruvate yielding NADH + H+ 3. Coenzyme A oxidizes Pyruvate FINAL PRODUCT is TWO Acetyl CoA molecules b. The Citric Acid Cycle/Krebs Cycle Coenzyme A transfers the 2-C acetyl group in the form of Acetyl CoA to the CAC/Krebs Cycle Glycolysis PREP rxn. (from prep rxn) Pg 141, Chpt. 8 CAC/ Krebs Cycle NADH 1. 2. 3. 4. Acetyl group joins with 4-C Oxaloacetate to form 6-C Citrate Oxidation occurs when NAD+ accepts e- (3X) and FAD accepts e- (1X) The acetyl group is oxidized to TWO CO2 molecules (4 total) Substrate level ATP synthesis occurs (an enzyme passes a high energy P to ADP to form ATP 5. A total of 6 CO2 molecules are produced, 2 from prep rxn, 4 from CAC per glucose molecule 6. NADH and FADH2 are carrying high energy Phosphates!! What happens to the high energy NADH and FADH2 molecules? • These molecules carry electrons to the ELECTRON TRANSPORT CHAIN in the CRISTAE of the mitochondria STEP I. NADH NAD+ + 2 H+ FADH2 FAD + 2 H+ -NADH and FADH2 bring electrons to the ETC -Both molecules are oxidized in order for ADP to produce ATP The ETC Players COMPLEX I- NADH-Q reductase (COMPLEX II- Succinate CoQ Reductase) COMPLEX III- Cytochrome b-c reductase COMPLEX IV- Cytochrome c Oxidase ATP SYNTHASE COMPLEX Cytochrome c Coenzyme Q NADH Hydrogen Ions ATP FADH2 Electrons ELECTRON TRANSPORT CHAIN pg 142 Electrons are passed from protein carrier to carrier via a series of oxidationreduction reactions. Protein Carriers: COMPLEX I NADH-Q reductase = An enzyme that catalyzes the transfer of electrons from NADH to Coenzyme Q Coenzyme Q/Ubiquinone = An enzyme that Transfers Electrons from Complex I and Complex II to Complex III Cytochrome b-c reductase/Complex III = helps build proton gradient Cytochrome c = electron carrier, transfers Electrons from one protein to another Complex II Succinate CoQ Reductase= oxidizes FADH2 Cytochrome c Oxidase/Complex IV = Electrons are transferred to oxygen to produce water STEP I. NADH NAD+ + 2 H+ FADH2 FAD + 2 H+ STEP II. NADH-Q reductase/Complex I gains electrons and is reduced. HYDROGEN IONS are pumped into the inner membrane space. Complex II oxidizes FADH2 to FAD + 2H+ STEP III. Electrons are lost to CoEnzymeQ which transfers the electrons to Complex III (cytochrome reductase) STEP IV. Hydrogen from the reduction of FADH2 from complex II are pumped to inner membrane space via Cytochrome reductase/ Complex III STEP V. Cytochrome c and coenzyme Q continuously shuttle electrons from complex to complex Cyt c and Coenzyme Q only transport electrons STEP VI. Oxygen accepts electrons from complex IV, cytochrome c oxidase, combines with hydrogen and produces H2O OXYGEN IS THE FINAL ACCEPTOR OF ELECTRONS IN THE ELECTRON TRANSPORT CHAIN!! Without oxygen, the electron transport chain would cease to function!! Death results if oxygen is not present because the body would not be able to produce/generate ATP Mitochondrial CRISTAE Matrix http://vcell.ndsu.edu/animations/atpgradient/first.htm As HYDROGEN IONS are pumped into the intermembrane space of the mitochondria, an electrochemical gradient develops. Ten times as many H+ are in the intermembrane space as there are in the matrix. This creates a strong [ ] gradient. Hydrogen ions will want to enter the mitochondrial matrix by flowing down the concentration gradient As hydrogen flows down the gradient via the ATP synthase complex, the enzyme ATP SYNTHASE synthesizes ATP from ADP + P ATP production depends on the H+ gradient!! ATP produced in the matrix is quickly shuttled out for use in body CHEMIOSMOSIS • Movement of Hydrogen Ions from innermembrane to the mitochondrial matrix MATRIX INNERMEMBRANE ATP SYNTHASE ATP Synthase • Is an enzyme • Produces ATP from hydrogen ions flowing down their concentration gradient FROM the inner mitochondrial membrane to the matrix • ATP is transported out of the matrix via an ATP channel protein • At any time, the amount of ATP in human body is only enough to sustain 1 minute of life. ATP synthase must work CONSTANTLY ENERGY YIELD from GLUCOSE METABOLISM 2 ATP from glycolysis 2 ATP from Krebs/ CAC cycle 32 or 34 ATP from Electron Transport Chain TOTAL = 36 or 38 ATP produced per 1 glucose molecule WHY??? 36 or 38 ATP In some cases: -2 NADH are produced during glycolysis -Sometimes NADH cannot cross mitochondrial membranes to go to ETC, but the e- from NADH can be shuttled -This shuttling costs the cell 1 ATP for each NADH that is shuttled which reduces the count of ATP from 38 to 36 -36 is the usual number of ATP produced How much energy is available to the cell per glucose? The difference in energy content between the reactants (C6H12O6 and O2) and products (CO2 and H2O) is 686 kcal ATP phosphate bond has 7.3 kcal 36 ATP are produced 7.3*36= 263 kcal Of the 686 kcal energy difference, 263/686 kcal of energy is transferred from glucose to ATP = 39%, the rest of the energy is lost as heat Metabolic Pool • Metabolic substrates are used over and over again • There is a “pool” or “holding area” of these substrates = Metabolic Pool • Metabolic pool substrates serve as entry points for the degradation or synthesis of larger molecules • Ex. Carbs, Fats and proteins Metabolic Pathways- 2 types 1- Catabolic (Catabolism)- break down Food molecules are the source of substrates (“pool”)- Fats, Carbs, Proteins Food molecules contain large amounts of stored energy in their chemical bonds Bonds are broken and food is broken down to basic subunits 2- Anabolic (Anabolism)- build up Molecules are formed from subunits in “pool”. Molecules are “re-formed” from the basic subunits. Fig. 8.11 pg 145 Metabolic Pool Concept Proteins, Carbs Fats are broken Down into their Basic subunits which Are ‘catabolized’ to Produce ATP Fatty acids can be used to Produce up to 108 ATP molecules! Fats are an efficient form of stored energy Plant and Tree Respiration How do plants respire? PHOTOSYNTHESIS!! The sun is the source of energy for producing carbohydrates in plants Energy flow occurs through a similar ETC in the chloroplasts in plant cells Photosynthesis v Cell Resp. Photosynthesis Cell Respiration -Thylakoid discs -ETC in thylakoid energized by sun -H+ electrochemical gradient -Calvin Cycle -NADPH -Cristae -ETC in cristae energized by glucose e-H+ electrochemical gradient -Citric Acid Cycle -NADH THIS WEEK IN LAB Membranes and Biological Transport You should all be experts on this!! QUESTIONS?? HOMEWORK Read all of Chapter 7- PHOTOSYNTHESIS Do all of the self test questions