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AP Biology Cellular Respiration Notes 9.1 Distinguish between fermentation and cellular respiration. Fermentation anaerobic (without O2) cytoplasm Produces ATP Partial degradation 9.2 Cellular Respiration aerobic (with O2). mitochondria Produces 18x more ATP Complete degradation More efficient & widespread Provide the overall chemical equation for cellular respiration. Compare the efficiency of this process in cells to the efficiency of a gasoline automobile engine. C6H12O6 + 6 O2 6 CO2 + 6H2O + energy (ATP + heat) 40% of the energy in 1 glucose is converted into the chemical energy of 38 ATP. 25% of the energy in gasoline is converted to kinetic energy. Exergonic with G of -686kcal / mole glucose 9.3 Define oxidation and reduction. Redox Reactions: release energy when electrons move closer to electronegative atoms. 9.4 Explain in general terms how redox reactions are involved in energy exchanges. Catabolic pathways transfer the electrons stored in food molecules, releasing energy that is used to synthesize ATP. Reactions that result in the transfer of one or more electrons from one reactant to another are oxidation-reduction reactions, or redox reactions. (Use “Stair step ETC” transparency) o The loss of electrons is called oxidation. (Oxid.# increases) o The addition of electrons is called reductions. (Oxid.# is reduced) In order to follow the energy you need only to “Follow the electrons.” 9.5 Describe the role of NAD+ in cellular respiration. NAD+ is a coenzyme (nicotinimide adenine dinucleotide) NAD+ is an oxidizing agent (i.e. it picks up electrons from molecules that are then oxidized) NAD+ is an electron carrier. It shuttles electrons to the ETC. Dehydrogenase is the enzyme that strips 2 e- and 2 H+ from organic molecules during the Krebs cycle. NAD+ picks up two electrons and one hydrogen ion (proton) leaving the other H+ in solution. NADH shows the one hydrogen that was picked up. The two e- make it neutral. Mrs. Loyd [email protected] Page 1 of 6 http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com 9.6 In general terms, explain the role of the electron transport chain in cellular respiration. To harness the energy in the electrons, the electrons are only allowed to decrease their distance from a nucleus a little bit at a time by passing the electron to increasingly electronegative molecules in the ETC. In so doing, H+ are translocated across the membrane to create the proton (H+) gradient which will be used to drive the Phosphorylation of ADP to ATP using ATPsynthase. 9.7 List the cellular regions where glycolysis, the citric acid cycle, and oxidative phosphorylation occur. Note whether substrate-level phosphorylation or chemiosmosis occur at each of these sites. Location Glycolysis Citric acid cycle Oxidative phosphorylation cytoplasm matrix of mitochondion across the inner membrane Substrate-Level Phoshorylation? Yes Chemiosmosis? No Yes No No Yes 9.7 Compare the reactants, products, and energy yield of the three stages of cellular respiration. Mrs. Loyd Page 2 of 6 [email protected] http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com Reactants 1. Glycolysis Glucose 2 ATP 2. Citric Acid Cycle 2 Pyruvate 2 Acetyl CoA + 2 CO2 3. Oxid. Phosph. Oxygen 12 NADH 2 FADH2 Products 2 Pyruvate 2 NADH 4 ATP (2 NADH) 6 NADH 2 FADH2 2 ATP 2 CO2 34 ATP Energy Yield in # of ATP 2 2 34 total = 38 ATP 9.9 Explain why ATP is necessary for the preparatory steps of Glycolysis. It is used to create a charge on the sugar which traps it in the cell. 2 ATP are required as Eact for the splitting of glucose. 9.10 Identify where substrate-level Phosphorylation and the reduction of NAD+ occur in Glycolysis. They occur in the energy payoff phase 9.11 Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and how this process links Glycolysis to the citric acid cycle. Occurs in the Matrix Products: CO2 + NADH + H+ + Acetyl CoA The acetyl group of Acetyl CoA will enter the Krebs cycle linking it to Glycolysis. 9.12 List the products of the citric acid cycle. Explain why it is called a cycle. Products: 2 CO2 + 3 NADH + 3 H+ + ATP + FADH2 To calculate the inputs and outputs on a per-glucose basis, multiply by 2, because each glucose molecule is split during Glycolysis into two pyruvate molecules. The carbon atoms that enter the cycle from acetyl CoA do not leave the cycle in the same turn. They remain in the cycle, occupying a different location in the molecules on their next turn after another acetyl group is added. How many times does the Citric Acid cycle turn to completely oxidize one glucose molecule? 9.13 Describe the point at which glucose is completely oxidized during cellular respiration. When it is all converted to CO2. This will require three turns of the cycle. 9.14 Distinguish between substrate-level Phosphorylation and oxidative Phosphorylation. Substrate-level: the formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism. Mrs. Loyd [email protected] Page 3 of 6 http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com Oxidative: The production of ATP using energy derived from the redox reactions of an electron transport chain. (Creating a H+ gradient and using it to drive ATP Synthase.) 9.15 In general terms, explain how the exergonic “slide” of electrons down the electron transport chain is coupled to the endergonic production of ATP by chemiosmosis. 1. Electrons are made available in the Citric Acid cycle. 2. The first protein in the ETC is reduced when it accepts e-‘s 3. The proteins of the ETC are arranged by increasing electronegativity 4. The proteins pull the e- back and forth across the membrane “exergonic slide” and translocate H+ in one direction creating a hydrogen ion gradient. 5. Hydrogen ions flow down their gradient thru ATP synthase driving the endergonic production of ATP. 9.16 Describe where and how the respiratory electron transport chain creates a proton gradient. Where: High hydrogen ion concentration is formed in the intermembrane space while low hydrogen ion concentration is in the matrix of the mitochondrion. How: The proteins of the ETC are arranged by increasing electronegativity. The proteins pull the e- back and forth across the membrane “exergonic slide” and translocate H+ in the intermembrane space creating a hydrogen ion gradient with the matrix. 9.17 omit 9.18 Summarize the net ATP yield from the oxidation of a glucose molecule by constructing an ATP ledger. See 9.7 9.19 omit 9.20 State the basic function of fermentation To produce ATP in the absence of oxygen. Fermentation is an extension of Glycolysis. Fermentation allows for the recycling of NAD+ so that Glycolysis can continue to be oxidized. Glucose becomes oxidized by losing e- to NAD+ and making NADH. NADH is oxidized by losing e- to the product of fermentation (reducing it) and becoming NAD+ again. 9.21 Compare the fate of pyruvate in alcohol fermentation and in lactic acid fermentation. Alcohol fermentation produces 2 carbon dioxide and 2 ethanol Lactic Acid fermentation produces 2 lactate (reduced lactic acid) 9.22 Compare the processes of fermentation and cellular respiration. Both use Glycolysis to oxidize glucose, but differ in their final electron acceptor. Aerobic Respiration yields 18x more ATP 9.23 Describe the evidence that suggests that Glycolysis is an ancient metabolic pathway. Gycolysis exists in nearly all organisms- it evolved early and was passed down Mrs. Loyd [email protected] Page 4 of 6 http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com Occurs in cytoplasm therefore does not require membrane-bound organelles, eukaryotes evolved 1 billion years after prokaryotes For nearly 1 billion years prokaryotes used glycolysis to make ATP because it does not need oxygen. Metabolic “heirloom” still functions in fermentation and first step in cellular respiration. Explain how the human body uses its daily supply of ATP. Minimum functions (maintenance) = 75% of calories taken in each day Voluntary Activity = varies according to activity 9.24 Describe how food molecules other than glucose can be oxidezed to form ATP. (Explain how polysaccharides, fats, and proteins are used as fuel for cellular respiration. Explain why a gram of fat yields more ATP than a gram of starch or protein.) The process of hydrolyzing (breaking down) carbs, lipids and proteins creates the smaller molecules that fit into the process of cellular respiration at appropriate steps. One gram of fat contains more calories than one gram of polysaccharides or proteins. 9.25 Explain how Glycolysis and the citric acid cycle can contribute to anabolic pathways. (Explain how nutrients are used in biosynthesis.) Intermediate molecules from the breakdown of glucose can be tapped as building blocks that the cell needs. Examples: Monosaccharides polysaccharides (starch, cellulose) Fatty acids and glycerol lipids Amino acids polypeptides (protein like muscle or enzymes) Mrs. Loyd [email protected] Page 5 of 6 http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com 9.26 Explain how ATP production is controlled by the cell, and describe the role that the allosteric enzyme phosphofructokinase plays in the process. Phosphofructokinase is an allosteric enzyme that responds to inhibitors and activators that help set the pace of Glycolysis and the citric acid cycle. Stimulated by: AMP (meaning it is low on ATP) Inhibited by products: ATP and citrate (4+2 = citrate or citric acid) Mrs. Loyd [email protected] Page 6 of 6 http://loydbiology.weebly.com 10/20/11 http://www.mybiology.com