BIOLOGICAL SCIENCES 330L Midterm Exam 2 Sample 11:00-11:50 a.m. or Prof. John Petruska 12:00-12:50 p.m. This exam (worth 175 points) is on five (5) pages Please answer all questions in the space provided. Please write your name and lab information below and also write your name on every page of the exam. Last Name _______________________________ ,First Name ________________ Lab Section (time and day)__________________________ TAs _______________ SCORE 1. (50) ________ 2. (20) ________ 3. (45) ________ 4. (40) ________ 5. (20) ________ TOTAL (175) __________Page 1 Last Name ______________________ First Name ______________ 1. (50 points) Fill in each blank with correct answer (2 pts/blank). (a) Name the human cellular compartment or organelle containing the largest amount of the following (2 pts/blank): DNA : ___________________________ rRNA: ______________________________ Histones:_________________________ RNA pol I:____________________________ Soluble Proteins____________________ Membrane Proteins____________________ Ribosomes+mRNA: _________________ Circular 16.5 Kb DNA ___________________ (b) Calculate the ionic strength of each of the following solutions: 1M NaCl ________________ 1 M (NH4)2SO4 _______________ 1M MgCl2 _______________ 5 M (NH4)2SO4 ______________ (show work) (c) Calculate the pH of each of the following solutions: 10 mM HCl _____________ 10-1 M NaOH _____________ 10-8 M HCl _____________ 10-8 M KOH ______________ (show work) (d) Of the common amino acid residues in proteins, ________________ and ________________ each have -1 charge at pH 7 ; _______________ and ________________ each have +1 charge at this pH. (e) Addition of salt to a protein solution decreases ______________________ attractions between protein molecules but increases _______________________ attractions. As a result, as salt is added, protein solubility initially ______________________ , but then decreases sufficiently to cause proteins to _________________________, so that they can be concentrated and removed (as a pellet) by _________________________.Page 2 Last Name ______________________ First Name ______________ 2. (20 points) (a) Write the full name (1 pts) and draw the chemical structure (2 pts) for each of the bases A,C,G,T and U in nucleic acids. A: C: G: T: U: (b) Explain why it is advantageous for DNA to have T instead of the base U used in RNA (5 pts).Page 3 Last Name ______________________First Name ______________5 3. (45 points) Write the full name (3, 4 or 5 points) and draw the chemical structure for each of the following (6, 8, or 10 pts ) (a) rU (3 + 6 pts) (b) dT (3 + 6 pts) (c) ATP (4 + 8 pts) (d) NADH (5 + 10 pts)Page 4 Last Name ______________________ First Name ______________ 4. (40 points) (1 pt/blank) The _____________- ____________ model for enzyme kinetics, k1 k2 E + S <----> ES ------> E + P k-1 assumes that _______is much less than [S} when v = [P]/____ is measured. According to this model, Rate of ES formation = ___ [___] [___] Rate of ES dissociation = (___ + ___)[____] At steady state, [___][___]/[____] = (___ + ___)/(___) = KM (a constant). Rate of P formation at steady state is v = ____ [ES], where [ES} = [___][___]/KM In terms of total enzyme concentration, [E]t = [___] + [___], the expression for v vs. ______has the form of a rectangular _______________, described as v = Vmax [___]/(___ + [___]), where Vmax = ___ [____]. (e) Three methods of obtaining linear plots with the above equation are: 1/v vs. 1/[S], called _________________________ plot [S]/v vs. [S], called _________________________ plot. v vs. v/[S], called __________________________ plot. (e) Identify the type of inhibition in each case: (1 pt/blank) (i) ___________________ inhibitor, which binds to E but not to ES, increases __________ but leaves ____________ unchanged (ii) ___________________ inhibitor, which binds to ES but not to E, _______________ Vmax and Km by same factor, so ________________ is unchanged. (iii) __________________ inhibitor, which binds to E and ES equally well, decreases ___________ but leaves ___________ unchanged.Page 5 Last Name ______________________ First Name ______________ 5.(20 points) Assuming the simple kinetic scheme (shown in question 4 )holds, (a) (10 pts) Sketch a plot of 1/v vs. 1/[S] without inhibitor (dashed line) and with competitive inhibitor (solid Line). Label intercepts and slope in each case. (b) (10 pts) Sketch a plot of [S]/v vs. [S] without inhibitor (dashed line) and with uncompetitive inhibitor (solid line). Label intercepts and slope in each