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Questions require interpreting titration curves, identifying amino acids by pKa values, explaining how nearby charged groups alter pKa, and comparing molecular interactions that stabilize or destabilize folded globular proteins.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/exam/","Exam",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/biochemistry-spring-2007-exam-1/455847/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/biochemistry-spring-2007-exam-1/455847.png","ImageObject",300,407,{"name":42,"@type":43},"EvelynWrites","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-10-07","2026-09-30",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",6,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"What do the exam reference constants and equations include?","Question",{"text":63,"@type":64},"The exam provides typical constants such as T=300K and pH=7.0, along with thermodynamics and equilibrium relations (e.g., ∆G0=-RTlnKeq) and other helpful formulas for acid-base and binding contexts.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"How are pKa values obtained from an amino-acid titration curve?",{"text":68,"@type":64},"The pKa values correspond to the inflection points on the titration curve, and the exam question expects identifying multiple pKa values from those features.",{"name":70,"@type":61,"acceptedAnswer":71},"Why does an Asp sidechain pKa decrease near an amino group and increase near a carboxylate group?",{"text":72,"@type":64},"Near an amino group, the deprotonated Asp negative charge is stabilized by the positive charge, making the acid stronger and lowering pKa. Near a carboxylate group, negative charge destabilizes the deprotonated state, making the acid weaker and increasing pKa.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},455847,1790820179,{"code":4,"msg":82,"data":83},"success",[84,88,92,95,100,104,109,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":89,"show_sort_weight":90,"slug":91},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":93,"slug":94},70,"exam",{"id":96,"doc_module":4,"doc_module_name":25,"category_name":97,"show_sort_weight":98,"slug":99},5,"Comic",60,"comic",{"id":55,"doc_module":4,"doc_module_name":25,"category_name":101,"show_sort_weight":102,"slug":103},"Technology",50,"technology",{"id":105,"doc_module":4,"doc_module_name":25,"category_name":106,"show_sort_weight":107,"slug":108},7,"Healthcare",40,"healthcare",{"id":110,"doc_module":4,"doc_module_name":25,"category_name":111,"show_sort_weight":112,"slug":113},8,"Research & Report",30,"research-report",{"id":115,"doc_module":4,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},9,"Religion & Spirituality",20,"religion-spirituality",{"id":117,"doc_module":4,"doc_module_name":25,"category_name":120,"show_sort_weight":117,"slug":121},"World Cup","world-cup",{"id":123,"doc_module":4,"doc_module_name":25,"category_name":124,"show_sort_weight":123,"slug":125},10,"Lifestyle","lifestyle",{"id":127,"doc_module":4,"doc_module_name":25,"category_name":128,"show_sort_weight":96,"slug":129},19,"General","general",{"code":4,"msg":82,"data":131},{"doc_id":79,"user_id":132,"nickname":42,"user_avatar":133,"doc_module":4,"category_id":33,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":115,"language":139,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":12,"update_tm":143,"read_time":144},687212989558,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","Biochemistry – Spring 2007 Exam 1 Name:   \nBiochemistry I-Exam Face Page  \n• This exam consists of 9 pages, including this one.  \n• There are a total of 90 points-or approximately 2 points /minute of exam time.  \n• Many questions have choices, if you answer more than one of the choices, your best answer will be counted.  \nThe following equations and constants may be useful: T=300K and pH=7.0 unless otherwise stated.  \nR=8.3 J/mol-K RT=2.5 kJ/mol @ 300K Log2=0.3 ln10=2.3  \nT(K) = T(C) + 273.  \nThermodynamics:  \n∆G0 = -RTlnKeq  \n∆G = ∆H-T∆SS = RlnW  \nln(an) = n ln a For the reaction: N ↔ U:  \n[U ]  \nK = ~~ ~~  \nEQ  \n[N ]  \nK  \nfU =  EQ   \n1+ KEQ  \nfN =  1   \n1+ KEQ  \n\n| Amino Acid Names:\u003Cbr>Alanine: Ala\u003Cbr>Arginine: Arg\u003Cbr>Asparagine: Asn\u003Cbr>Aspartic Acid: Asp\u003Cbr>Cystine: Cys\u003Cbr>Glycine: Gly\u003Cbr>Histidine: His\u003Cbr>Isoleucine: Ile\u003Cbr>Lysine: Lys\u003Cbr>Leucine: Leu\u003Cbr>Methionine: Met | Phenylalanine: Phe\u003Cbr>Proline: Pro\u003Cbr>Serine: Ser\u003Cbr>Threonine: Thr\u003Cbr>Tryptophan: Trp\u003Cbr>Tyrosine: Tyr\u003Cbr>Valine: Val\u003Cbr>Glutamine: Gln\u003Cbr>Glutamic Acid: Glu |\n| --- | --- |\n\nAcid-Base & Buffers  \npH = pKa + log ~~ ~~[[A−HA]]  \nR = 10pH − pKa  \n[HA] = [ AT] ~~ ~~1R  \n− R  \n[ A ] = [ AT]  1+ RBeer's law:  \nA=ε[X]l  \nε λ=280 = 5,000 for Tryptophan (Trp)  \nελ=280 = 1,500 for Tyrosine (Tyr)  \nLigand Binding:  \nFor [M]+[L] ↔ [ML] KEQ = ~~ ~~kkoofnf~~ ~~  \nθ = ~~ ~~[M[]L[M]~~ ~~L] = ~~ ~~KD[][L]  \n1: _________ / 9  \n2: _________ / 6  \n3: _________ /12  \n4: _________ / 8  \n5: _________ /12  \n6: _________ / 6  \n7: _________ /11  \n8: _________ /14  \n9: _________ /12  \nTOTAL: _________ /90  \nBiochemistry – Spring 2007 Exam 1 Name:   \n1. (9 pts) A titration curve of an amino acid is shown on the right. Please answer the following questions.  \ni) What are the pKa values associated with this amino acid? Briefly explain how you got these values (3 pt) .  \nThe pKa values are 2, 6 and 9. (1 ½ pt)  \nThese were obtained from the three inflection points on the titration curve (1 ½ pts)  \nii) Mark one pH range on this curve where this amino acid would serve as a buffer. Briefly justify your answer (3 pts) .  \nAny of the pKa values can be used +/ -1 pH unit: 1-3  \n5-7  \n8-10  \n(However, my titration as drawn suggests a slightly narrower range)  \niii) Select from the choices of sidechains below, the amino  \n\n| pH Titration |  |  |\n| --- | --- | --- |\n| pH | 12\u003Cbr>11\u003Cbr>10\u003Cbr>9\u003Cbr>8\u003Cbr>7\u003Cbr>6\u003Cbr>5\u003Cbr>4\u003Cbr>3\u003Cbr>2\u003Cbr>1\u003Cbr>0 | |\n| 0 0.5 1 1.5 2 2.5 3\u003Cbr>Eq. Base |  |  |\n\nacid that would most likely produce the above titration curve. Write the approximate pKa for its sidechain next to its structure on the diagram below. Give the name of this amino acid (3 pts) .  \nA  \nN  \nB is the correct answer– histidine, with a pKa of 6.0. The pKa at 2.0 is the carboxyl group, the pKa at 9.0 is the mainchain amino group. A (phenylalanine) is incorrect because it has no ionizable group on its  \nsidechain. C (lysine) is incorrect because the pKa of its sidechain is 9.0.  \n2. (6 pts) The pKa of the carboxyl group in the sidechain of aspartic acid (Asp) is 4.0. In alanine (Ala), the pKa of the mainchain carboxyl is 2.0. Please answer either of the following two choices. Circle your choice.  \nChoice A: When the Asp sidechain in a protein is close to an amino group, its pKa usually decreases, why?  \nA smaller pKa indicates a stronger acid, i.e. the deprotonated state is energetically more favorable. In this case the negative charge on the deprotonated Asp is stabilized by the positive charge on the amino group.  \nCH3  \nO +  \nNH 3  \nO  \nAlanine  \nChoice B: When the Asp sidechain in a protein is close to another carboxylate group, its pKa usually increases, why?  \nA larger pKa indicates a weaker acid, i.e. the deprotonated state is energetically less favorable. In this case the negative charge on the deprotonated Asp is destabilized by the negative charge on the carboxylate group.  \nBiochemistry – Spring 2007 Exam 1 Name:   \n3. (12 pts) Select one of the following four interactions or effects. Briefly","cbCaid4zLbmGZkyf","https://ap.wps.com/l/cbCaid4zLbmGZkyf","pdf",170830,"English","# Biochemistry I-Exam Face Page\n## Exam format and reference equations\n## Amino acid names and abbreviations\n## Acid-base and buffers (pH, pKa)\n## Thermodynamics and equilibrium relations\n## Spectroscopy (Beer’s law)\n## Ligand binding and binding parameters\n# Questions\n## Q1 Titratation curve pKa values, buffer range, and amino-acid identification\n## Q2 pKa shifts for Asp sidechain near amino group or carboxylate\n## Q3 Interactions/effects in protein folding and stabilization ranking\n## Q4 α-helix vs β-sheet similarities and differences","[{\"question\":\"What do the exam reference constants and equations include?\",\"answer\":\"The exam provides typical constants such as T=300K and pH=7.0, along with thermodynamics and equilibrium relations (e.g., ∆G0=-RTlnKeq) and other helpful formulas for acid-base and binding contexts.\"},{\"question\":\"How are pKa values obtained from an amino-acid titration curve?\",\"answer\":\"The pKa values correspond to the inflection points on the titration curve, and the exam question expects identifying multiple pKa values from those features.\"},{\"question\":\"Why does an Asp sidechain pKa decrease near an amino group and increase near a carboxylate group?\",\"answer\":\"Near an amino group, the deprotonated Asp negative charge is stabilized by the positive charge, making the acid stronger and lowering pKa. Near a carboxylate group, negative charge destabilizes the deprotonated state, making the acid weaker and increasing pKa.\"}]","Biochemistry - Spring 2007 Exam 1 | PDF",1790744469,23]