CHEM-342 Introduction to Biochemistry Name ________________________ Final Examination - Individual Part Monday, 26 May 2003 7:00 - 8:45 PM H. B. White - Instructor Important - Please read this before you turn the page. $ This examination will assess your learning, problem-solving skills, and ability to communicate clearly. It is intended to be challenging even to the best students in the class. Writing reflects how you think. Among the “right answers” I will read for the following questions, some will be better than others because they show greater depth of understanding, avoid extraneous or inaccurate information, provide a more logical structure, use appropriate examples, and choose words with precision. Better quality answers will receive higher marks. Therefore organize your thoughts before you write. Strive to write not that you may be understood, but rather that you cannot possibly be misunderstood. Stream of consciousness answers are rarely well organized or clearly presented. $ There are 9 pages to this part of the examination. Please write your name on each page. $ Part I (80 points) This individual part of the examination, includes 11 problems and short essay questions. Also, you can obtain up to 17 additional points from bonus questions. Part II (25 points) The group part of the examination includes 3 problems and a 5 point bonus question. $ If you complete Part I early, you may leave the room for a break and return at or before 8:45 PM when Part II begins. $ You may refer to your notes, course reader, handouts, or graded homework assignments. $ Attempt to draw a picture or diagram as part of your answer to every question. $ Graded examinations may be picked up Thursday morning, 29 May. $ Have a relaxing and safe Summer.CHEM-342 Introduction to Biochemistry Name________________________________________ Final Examination-Individual Part, 26 May 2003 Page 2 1. (5 points) You were asked to attend two biochemistry-related research seminars this semester. Describe one. (Speaker, topic, anything you learned) 2. (5 points) Crystals of deoxyhemoglobin crack and disintegrate when exposed to oxygen. What would be a reasonable explanation for this? 3. (4 points) When present, what does jaundice indicate? 4. (5 points) As is shown in the metabolic pathway below, threonine, an amino acid with two chiral centers, along with pyruvate provide carbon for the biosynthesis of isoleucine, the only other common amino acid with two chiral centers. PutCHEM-342 Introduction to Biochemistry Name________________________________________ Final Examination-Individual Part, 26 May 2003 Page 3 circles around the carbon atoms of isoleucine that are derived from pyruvate. [Trivia: For reasons unknown, isoleucine is the only amino acid of the common 20 amino acids that is not usually present in human hemoglobin.] 5. (6 points) Red blood cells contain lots of glutathione (GSH), the tripeptide shown below. Among other things, GSH protects cells by scavenging reactive oxidants and forming the GSSG oxidized dimer (see question 9). In the space below, draw the structures of the three amino acids generated in the complete acid hydrolysis of glutathione. Identify each of the amino acids.CHEM-342 Introduction to Biochemistry Name________________________________________ Final Examination-Individual Part, 26 May 2003 Page 4 6. (5 points) The following is a short news item from the Wilmington News Journal Wednesday, 21 May 2003. OXFORD, Iowa – A father who went to get help after his SUV got stuck along a water-logged rural road returned to find his wife and five children unconscious from carbon monoxide poisoning. His oldest child, 9 year old Cassandra, died after the accident. The other children ages 8, 4, 3, and 16 months remained in guarded condition the family said Monday. The mother Debra Maier, 29, was released from the hospital. Explain the cause of death in carbon monoxide poisoning?CHEM-342 Introduction to Biochemistry Name________________________________________ Final Examination-Individual Part, 26 May 2003 Page 5 Problem-Solving With hemoglobin comprising more than 90% of the protein in a red blood cell, it might seem that the remaining protein is insignificant. Not so. For example, enzymes and other red cell proteins perform vital metabolic roles. Due to the absence of mitochondria, red blood cell metabolism proceeds almost anaerobicly in the midst of oxygen surplus. Bathed in plasma maintained at ~5mM glucose, red cells use glucose via glycolysis and the pentose phosphate pathway to sustain hemoglobin function. 7. (10 points) One of the compounds formed in the breakdown of glucose to pyruvate and lactate in red cell glycolysis is 2,3-diphosphoglycerate (DPG), the structure on the left. In mammalian red blood cells, the concentration of DPG matches that of hemoglobin. It binds tightly, one mole per deoxyhemoglobin tetramer, but does not bind to oxyhemoglobin, as is depicted in the equation below. Hb(O2)4 + DPG ↔ Hb•DPG + 4O2 In the absence of DPG, hemoglobin binds oxygen about 10 times more tightly than it does in a normal red blood cell. Part of the acclimatization that occurs when people go to high altitudes is the physiological adjustment of DPG levels to optimize the binding and release of oxygen at the lower oxygen pressures. (8 points) In the space below, draw and label a diagram relating the percent saturation of hemoglobin with and without DPG as a function of oxygen partial pressure. Then draw a dashed line corresponding to the binding properties needed at high altitude. 100 % Saturation of Hemoglobin CapillaryOxygenAtmospheric OxygenPartial Pressure of Oxygen0 (2 points) Predict whether the concentration of DPG in red blood cells increases or decreases in people at high altitude. Explain your prediction. 3 point bonus: Does DPG bind to the heme group in deoxyhemoglobin? Explain.CHEM-342 Introduction to Biochemistry Name________________________________________ Final Examination-Individual Part, 26 May 2003 Page 6 8. (10 points) “Role of Free Radicals in Red Cells” Oxygen is a highly reactive molecule that is toxic to anaerobic cells that cannot use or destroy it. In the red cell, oxygen occasionally does react and the red cell contains systems coupled to glucose metabolism