Name_________________________________________Section_________7.014 Problem Set 1Answers to this problem set are to be turned in at the box outside 68-120 by 4:00 pm,Wednesday, February 13. Problem sets will not be accepted late. Solutions will be posted onthe web. (http://web.mit.edu/7.01x/www/intro.htm).*The problem sets are designed as a tool to allow you to practice and test yourknowledge of the concepts covered in class and in section. It is important thatyou work through each problem set for yourself. All thoughtful answers meritcredit.Question 1A carbon atom with four different substituent groups is asymmetric and is called a chiralatom or, if it its part of a larger molecule, a chiral center. A chiral molecule can exist intwo forms or stereoisomers that have different conformations in space.a) Do the chemical properties such as surface tension, viscosity, density, or boiling pointsof the two forms differ?b) The stereoisomers of carvone, designated R- and S-, are found in some plants. Humansrecognize R-carvone as spearmint, and S-carvone as caraway.i) Why does a particular plant produce only one version of carvone?ii) How can the human sensory system distinguish between the two versions ofcarvone?c) Aspartame, the artificial sweetener called NutrasweetTM, is L-Aspartyl-L-phenylalanylmethyl ester.i) Is aspartame a protein?2ii) Would you predict the stereoisomer of aspartame, L-Aspartyl-D-phenylalanylmethyl ester, tastes sweet to humans?3Question 2Below are two representation of phospholipids, one shows the formula, the other two areiconic views.C O C OCH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2O OC CHH2CH2O OOOPCH2HCCOOH3NH+__a) Box the hydrophilic portion on each drawing.b) Using the iconic representation, draw a phospholipid micelle in an aqueousenvironment. Indicate where water would be found.4Question 2, continuedc) Lipid bilayers are selectively permeable. Hydrophobic molecules and small unchargedpolar molecules such as O2, CO2, H2O, and glycerol can cross the membrane.i) Would you expect a lipid membrane to be permeable to carbohydrates? Explain.ii) If your answer to (i) is no, how would the carbohydrates needed for cellularfunction enter the cell?iii) What are three uses for carbohydrates within the cell?d) The length of the hydrocarbon chain and the number of double bonds it contains affecthow a phospholipid behaves in a membrane and hence the permeability of thatmembrane.i) Would you expect a membrane composed of phospholipids with longhydrocarbon chains to be more or less permeable than a membrane composed ofphospholipids with short hydrocarbon chains? Explain.ii) Would you expect a membrane composed of many unsaturated fatty acids to bemore or less permeable than a membrane composed of saturated fatty acids?Explain.5Question 3a) For the pairs given below draw the amino acids and give the strongest type ofinteraction that occurs between the side chain groups . Do not include hydrophobicinteractions.i) tyrosine, asparagineii) cysteine, cysteineiii) isoleucine, valineiv) glutamic acid, lysinev) glycine, glutamine6Question 4The drug Minoxidil is used orally as an agent against hypertension and topically as a stimulantfor hair growth. Assume that at pH 7, Minoxidil has the following structure.H N2NNNMinoxidilNH2b) Below is a schematic of a Minoxidil binding site on a hypothetical protein.i) Draw how Minoxidil would bind within this binding site, based on the structureof the compound and the amino acids highlighted on the schematic. Model BVal 129Leu 134Glu 51Asn167ii) Fill out the table below with the interactions that occur between the specifiedamino acids and Minoxidil in the model you have proposed.Amino acid Interaction with MinoxidilGlu 51Val 129Leu 134Asn 1677Question 4c) To decide if your model is correct, you construct some altered versions of this proteinand test whether Minoxidil still binds. All other amino acids remain constant. The resultsare as follows:Protein Position 51 Position 129 Position 134 Position 167 Binds?normal Glu 51 Val 129 Leu 134 Asn 167 yesvariant 1 Asp 51 Val 129 Leu 134 Asn 167 yesvariant 2 Gly 51 Val 129 Leu 134 Asn 167 yesvariant 3 Gly 51 Val 129 Leu 134 Ala 167 novariant 4 Glu 51 Lys 129 Leu 134 Ala 167 novariant 5 Glu 51 Phe 129 Leu 134 Asn 167 yesi) Is your model consistent with the results given above? Explain. (If the answer is no, please propose a new model consistent with the above data)ii) Explain in terms of your model and the likely interactions why•variant 2 will bind Minoxidil but variant 3 will not bind Minoxidil.•variant 5 will bind Minoxidil but variant 4 will not bind Minoxidil.8 ALANINE(ala)ARGININE(arg)ASPARAGINE(asN)CCOOHNH3CH3-+CCOOHNH3CHCH3CH3-+CCOOHNH3CH2CH2CH2NHCNH2NH2-++CCOOHNH3CH2CONH2-+CCOOHNH3CH2COO-+-ASPARTIC ACID(asp)CCOOHNH3CH2SH-+CYSTEINE(cys)CCOOHNH3CH2CH2OOC-+-CCOOHNH3CH2CH2OCNH2-+CCOOHNH3H-+CCOOHNH3CH2CNCNHHHH-++CCOOHNH3CHCH3CH2CH3-+CCOOHNH3CH2CHCH3CH3-+CCOOHNH3CH2CH2CH2CH2NH3+-+CCOOHNH3CH2CH2S CH3-+CCOOHNH3CH2H HHHH-+CNCH2CH2CH2HHH-COO+CCOOHNH3CH2OH-+CCOOHNH3CHOHCH3-+CCOOHNH3CH2-+CCOOHNH3CH2OHH HHH-+GLUTAMIC ACID(glu)GLUTAMINE(glN)GLYCINE(gly)HISTIDINE(his)ISOLEUCINE(ile)LEUCINE(leu)LYSINE(lys)METHIONINE(met)PHENYLALANINE(phe)PROLINE(pro)SERINE(ser)THREONINE(thr)TRYPTOPHAN(trp)TYROSINE(tyr)VALINE(val)STRUCTURES OF AMINO ACIDSCNHHHHHHat pH
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