Unit 1 Key

Unit 1 Key - Gerhart Key Unit 1 Review Problems Bis2A To...

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Gerhart 4/30/2008 Key: Unit 1 Review Problems Bis2A To help you gauge your understanding of the material, the answers to a selection of questions from the supplemental reading assignments are below in blue. These problems can also be found within the assigned supplementary readings on the website. Introduction: Part 2, Chemical Evolution (Lecture 3) 1.Biologists often use the term energy source as a synonym for “electron donor”. Why? In biological systems, electrons moving from one molecule to another are equal to the movement of energy from molecule to another. An electron donor has energy in the form of electrons. For instance, glucose is an energy source; during glycolysis, glucose donates electrons to NAD + , forming NADH. NADH is an energy storage molecule, like ATP, that can be used by the cell as an energy source to drive unfavorable reactions forward. Not unlike glucose, NADH can also donate its electrons to another enzyme in order for work to be done. NADH often donates electrons to the electron transport chain, what work is being done here? 2. A lucky little microorganism living on early Earth has the ability to ask you for advice. There are several possible fuels in the environment and the microorganism is confused about which to use. Use your understanding of redox chemistry to determine which redox couples the microorganism should use to harvest the most energy possible. Which redox couples would be the worst for the microorganism to use? Redox couple E 0 2H+/H 2 -0.42 NO 3 -/NO 2 - +0.42 ½ O 2 /H 2 0 +0.82 S/H 2 S -0.28 Best redox couple: H2 + ½ O2 Æ H2O Energy released is proportional to (0.42 (reverse sign because running reaction in opposite direction) + 0.82) * 2 electrons – this is a large change in energy. Worse redox couple: H2 + S Æ H2S Energy released is proportional to (0.42-0.28) * 2 electrons – this is a small change in energy. Metabolism part 2, Glycolysis and Fermentation (Lecture 4) 1. Describe the roles played by ATP and NAD + in metabolism. What particular features of their structures allow them to perform those functions? ATP and NAD + act as energy storage molecules that couple exergonic and endergonic reactions. In the case of NADH, the energy is carried with electrons to allow coupling of redox reactions. ATP contains two high-energy phosphate bonds that release energy upon breaking. In effect, ATP can be used twice; one cleavage produces ADP and a free phosphate group, and the second cleavage produces AMP and another free phosphate group. NAD + , a dinucleotide consisting of an adenine base and a nicotinamide ring, can pick up two electrons, as NADH +H.
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Gerhart 4/30/2008 3. In the following redox pairs, which compound is reduced and which is oxidized? A.
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Unit 1 Key - Gerhart Key Unit 1 Review Problems Bis2A To...

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