NAME________________________________TA______________Section #______17.013 Spring 2005 Problem Set 1FRIDAY February 11, 2004Problem sets will NOT be accepted late.Question 1a) Circle the correct answer.i) Homo sapiens emerged ____________years ago.5,000 50,000 500,000 5,000,000 50,000,000ii) There are __________________billion letters (bases) in the human genome.one three thirty 3 hundrediii) An alpha helix is an example of _________________structure.primary secondary tertiary quarternaryb) What are the four major types of biological molecules discussed in lecture? Whatmonomers make up these molecules? Give one important function of each type ofbiological molecule in the cell.Name of moleculeMonomerOne function of the PolymerMIT Department of Biology7.013: Introductory Biology - Spring 2005Instructors: Professor Hazel Sive, Professor Tyler Jacks, Dr. Claudette Gardel2c) Name the molecules depicted below.OCH2OPONNNNNH2OH HO--H HHOPOO-OH HOH C2H HadeninethymineHOPOO-OH HOH C2HOH HHNHNOONNNNNH2adenineCH3DNAOCH2OPONNNNNH2OH HO--H HOPOO-OH HOH C2H HadenineuracilOPOO-OH HOH C2HOH HNHNOONNNNNH2adenineOHOHOHCC CC COOC CCONH N NNCHH H HOO(CH ) (CH )C COONH+CHCHH CH H H HNHCONHNH+CH3322 22 2 2 2233RNAProteind) Circle one peptide bond if there is any in the figures above.3Question 2a) Draw the energy profile for this reaction. Refer to Chapter 6 in the textbook.A + B ---------> C + D ΔGo' = -3.4 kcal/molOn the diagram be sure to…1) show relative energy levels of the reactants and the products.2) label the axes.3) label reactants and products.4) indicate the energy of activation.5) indicate ΔG.b) An enzyme _____________ the activation energy of a reaction.lowers raises does not affectc) An enzyme _____________the ΔG of a reaction.lowers raises does not affectd) Using a dashed line in the above diagram, draw the energy profile in the presence of anenzyme.4Question 3Some receptors are transmembrane proteins found on the cell surface.CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH HH2COPOOOCH2CH 2CH2CH2CH2CH2CH2CH2CH2CH2COOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH HH2COPOOOMembrane––––––––CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOMembrane––––CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2C OOC COOCCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HHHH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH HH2COPOOOCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH HH2COPOOO––––––––CHCHCHCHCHCHCHCHCHCHCOOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH HCHCHCHCHCHCHCHCHCHCHCOOCCOO CCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2HH H2222222222H2COPOOO2222222222H2COPOOO––––intracellularextracellulargrowth factor receptorsa) The majority of the molecules that constitute a membrane belong to what class ofmacromolecules? ________________________________b) Explain the important qualities/properties of these molecules that allow them to formmembranes.Receptor proteins5A smaller schematic of the receptor is shown here.]Sequence from this region shown below= transmembrane regionc) Which stretch of amino acids in the above sequence is within the interior of thetransmembrane region of the receptor? Circle these amino acids and briefly explain yourreasoning below.When a “LIGAND” binds to the extracellular domain of the receptor, a conformationalchange occurs in the receptor. Ligand binding causes dimerization of two adjacentreceptors in the cell membrane. Upon dimerization, the intracellular domains of thereceptors become activated. See schematic below.active domainsintracellular domainligand Receptor 1 Receptor 2inactive domains plasma membraneextracellullar ligand- binding domainligand NH3+···Ile-Val-Phe-Leu-Ala-Val-Trp-Met-Phe-Arg-Lys-Thr-His···COO-6c) Regions of the two receptors that interact upon dimerization are drawn below. Inparts (i - iv) below, name the strongest type of interaction (choose from; hydrogen bond,ionic, covalent, van der Waals) that occurs between the side chains of the amino acidsindicated.OCH2SCH2+CHCOCH3SCOSAsp68OHCH2CH2CH2CH2Ser53Cys36Ala45-Phe50Cys82Cys75CH2CH2H2NGln12CH2CH2CH2CH2H3NLys65H3CH3CVal98Receptor 2Receptor 1HInteracting Side chainsType of interactioni) Phe50 : Val98ii) Asp68 : Lys65iii) Cys75 : Cys82iv) Ser53 : Gln12d) Gln12 is the 12th amino acid in primary sequence. Val 98 is the 98th amino acid in theprimary sequence. Explain how these amino acids are far apart in the primary sequence ofthe protein yet are close to each other in the region of the protein diagrammed above.7e) Molecular interactions between the two receptors are important for dimerization.Thus, substitution of certain amino acids in the protein can affect receptor dimerization.Predict whether the receptors will or will not be able to dimerize given the substitutions(i - iv) below. EXPLAIN your reasoning.i) Asp68 → Argii) Ser53 → Thriii) Phe50 → Asniv) Val98 → Ilef) Substitution of one amino acid, Cys75 → Gly, leads to dimerization of the receptorswith or without ligand. Provide a brief explanation for this observation.8Question 4You have identified a new, rapidly reproducing species of dog that you have named the “mitbull”. Themitbull is diploid and two autosomal chromosomes are shown. One chromosome carries gene A withtwo alleles designated A and a. The other chromosome carries gene B with two alleles designated Band b.a) Diagram mitosis in a heterozygous (AaBb) mitbull cell shown below. Draw your diagrams in theoutlines of the ovals adjacent to the stages. Include the alleles and the mitotic spindle in yourdiagrams.ProphaseMetaphaseMitbull cellAaBb9b) Indicate the genotype of cells that would result after telophase. ____________AnaphaseTelophasephase10c) A cell in Metaphase I is shown below where a crossover event takes place. Diagram theindicated stages in meiosis. Designate the alleles and the spindle.Metaphase IITelophase IAAaaBBbbTelophase II11d) You determine another gene, gene D, maps 20 cM or map units away from gene A.i) Given the cell with chromosome configuration below, what would be the
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