1 Biochemistry I, Fall 2007 Name:____________________________________ Exam III - Face Page – This exam has a total of 8 pages, including the face page. General Thermodynamics T = 300K and pH = 7.0 unless otherwise stated. R = 8.3 J/mol-K S = R ln W ΔG° = ΔH° - TΔS° ΔG° = -RT ln KEQ ΔG° = -nFΔE° ΔG = RTln[c2]/[c1] + ZFΔV2 Part A (28 pts) Multiple choice. Please circle the best answer (2 pts each). 1. Phospholipids are composed of a) three fatty acids esterified to a glycerol backbone. b) a head group, a phosphate group and two fatty acids esterified to glycerol. c) a head group, two fatty acids and a phosphate group linked to glycerol through a phospho-anhydride linkage. d) two fatty acids and a head group esterified to cholesterol. 2. Phospholipids a) do not interact with water. b) assemble into a lipid bilayer in the absence of energy input. c) are covalently linked to one another through thio-ester bonds. d) are the sole constiuents of biological membranes. 3. The transport of a charged solute across a biological membrane a) occurs only if the solute is moving down its concentration gradient. b) is facilitated by channels and always requires energy input. c) can be directly coupled to ATP hydrolysis. d) cannot be directly coupled to ATP hydrolysis. 4. The Na+/K+ ATPase a) uses ATP to pump both Na+ and K+ up their respective concentration gradients. b) uses ATP to pump both Na+ and K+ up their respective electrical gradients. c) transports Na+ and K+ across the membrane by facilitated diffusion. d) couples the movement of Na+ and K+ to ATP synthesis. 5. The difference between glucose and fructose is that a) glucose can be phoshorylated and fructose cannot. b) glucose is a ketose and fructose is an aldose. c) glucose is an aldose and fructose is a ketose. d) glucose but not fructose is a substrate for glycolysis. 6. Glycogen consists of ______ linkages between _______ subunits and cellulose consists of ______ linkages between ______ subunits. a) α 1-4, glucose, α 1-6, glucose. b) α 1-6, glucose, α 1-4, mannose. c) β 1-4, mannose, α 1-4, glucose. d) α 1-4, glucose, β 1-4 glucose. 7. Starch and cellulose a) are both cleaved by α-amylases in the saliva. b) are both highly branched structures. c) both form β-sheets. d) differ in secondary structure.3 8. Fatty acids provide the richest source of energy when they are a) oxidized to pyruvate and used for gluconeogenesis. b) oxidized through the TCA cycle. c) reduced to regenerate NAD+ for the TCA cycle. d) taken up by the brain and oxidized by NADH. 9. When oxygen is plentiful in eukaryotic cells, most of the newly synthesized ATP is produced in the a) cytoplasm. b) inner mitochondrial membrane. c) mitochondrial matrix. d) space between inner and outer mitochondrial membranes. 10. The electron transport chain consists of the sequential transfer of electrons a) from ATP to NAD+. b) from NADH to ATP. c) from NADH to O2. d) from NAD+ to O2. 11. Glycolysis is regulated a) at every step. b) only at the committed step mediated by phosphofructokinase (PFK). c) directly by cAMP binding to hexokinase. d) to maintain sufficient ATP for the cell’s needs. 12. Coenzyme Q a) accepts electrons directly from NADH and FADH2. b) has a higher redox potential than NADH. c) has a higher redox potential than O2. d) is lipid soluble only in the reduced form. 13. Several oxidative decarboxylation steps in the utilization of glucose involve a) reduction of NAD+ and release of CO2. b) oxidation of NADH and release of CO2. c) reduction of FAD and release of water. d) oxidation of FAD and the addition of water. 14. The F1/Fo ATP synthase a) conducts protons. b) conducts electrons. c) conducts neither protons nor electrons. d) conducts both protons and electrons.4 B1. (12 pts) Please answer three of the following four questions concerning biological membranes. Choice A: Briefly discuss the forces that drive assembly of a phospholipid bilayer. Choice B: Briefly discuss the importance of membrane impermeability in the production of ATP. Choice C: Calculate the free energy required to pump a Ca+2 ion out of a cell when the cytoplasmic concentration is 0.4 µM and the extra-cellular concentration is 1.5 mM, and the membrane potential is -60 mV (inside negative). Assume a temperature of 310 K. Choice D: Briefly discuss the characteristics of a membrane-spanning domain in an integral membrane protein, including the types of secondary structures commonly found to span the membrane.5 B2. (8 pts) Please answer one of the following two questions. Choice A: Describe the mechanism of ATP synthesis by the F1/Fo synthase. Your description should include the conformations of the catalytic subunit as well as an explanation of how proton flow is coupled to ATP formation. A clear, well-labeled diagram may suffice. You need not discuss the mechanism of c-ring rotation. Choice B: Describe the electron transport chain beginning with NADH and FADH2 and ending with O2. Your description should include the major complexes, the number of protons pumped by each as well as the major diffusible electron carriers. A clear, well-labeled diagram may suffice.6 B3. (16 pts) For the reactions listed below, indicate whether each, on its own, is an endergonic or exergonic reaction. Reaction Endergonic or Exergonic? Formation of ATP from ADP + Pi Formation of a thio-ester linkage Reduction of a fumarate to succinate Transfer of 2 electrons from cytochrome c to O2 Facilitated diffusion of K+ across membranes Cleavage of a phosphate group from fructose 1,6 bisphosphate Conversion of an aldehyde to a carboxylic acid Flow of protons into the mitochondrial matrix B4. (16 pts) For four of the following five reactions, indicate the type of reaction (eg, dehydrogenation), the cellular location in which the reaction occurs (eg, cytoplasm), and at least one co-factor or co-substrate (eg, ATP) of the reaction. Reaction Type of reaction Location Co-substrate HCOCOHHCH2OPO3-2CCOHHCH2OPO3-2OOPO3-2COO-CCOHH-OOCHCH2COO--OOCCC-OOCHCH2COO-OH3CCOCOO-H3CCOSCoAOSCoAOHOSCoAOH3CCOCOO-H3CCOHCOO-7 B5. (8 pts) Please choose from one of the following three questions. Choice A: Describe, step by step, how a drop in blood glucose leads to the coordinate regulation of glycolysis and