Spring08_MidtermI_Exam_KEY

Spring08_MidtermI_Exam_KEY - MCB102 MIDTERM EXAM Name...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
MCB102 MIDTERM EXAM February 27, 2008 Name ________________________________ Student ID_____________________________ Mean: 72.19 Standard deviation: 14.44 1 Question Points 1 (10 pts) 2 (14 pts) 3 ( 8 pts) 4 (10 pts) 5 (15 pts) 6 (10 pts) 7 (08 pts) 8 (15 pts) 9 (10 pts) Total _____/100
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Some information you may need: Henderson-Hasselbalch equation: pH = pK a + log([A - ]/[HA]) Michaelis-Menten equation: v o = V max [S]/K m + [S] 1. (10 points) While working in a research lab over Spring break, your supervisor asks you to make a buffer solution. She knows that you learned how to make buffers in MCB102 and asks you to come up with your own recipe. You are asked to make 500 mL of phosphate buffer at 0.5 M concentration and final pH of 6. You have the following solutions on the chemical shelf in the laboratory: 1M H 2 PO 4 - (pK a of dihydrogen phosphate is 6.86) 0.5M KOH How much of each solution would you mix to make the buffer? (You will have to add the appropriate amount of water to fill up to 500 mL at the end) Ans: 3 points total for 250mL 1M H 2 PO 4 2- : For 500 mL 0.5M phosphate: (0.5M H 2 PO 4 - )(500 mL) / 1M H 2 PO 4 - = 250 mL Same points if no calculator (can do this by hand) 6 points total for 61mL 0.5M KOH: 2 points: 6 = 6.86 + log A-/HA A-/HA = 0.14 Could leave as 10^-0.86 if no calculator 1 point: HA + A- = (0.5L)(0.5M) = 0.25 mol Same points if no calculator 2 mL of 1M H 2 PO 4 2- mL of 0.5M KOH mL of H 2 O
Image of page 2
2 points (solving for moles): A- = 0.0307 mol have to be converted 1 point (converting to mLs): (0.0307 mol KOH) / (0.5 M) = 0.061 L KOH = 61 mL No calculator: describe in words that you would use the 2 equations with 2 variables to solve for moles of A- then add equivalent moles of KOH. Then you calculate volume of KOH by dividing moles by concentration. 1 point for 189mL water (if the other volumes were wrong, you could still get this point) 500 mL – 250 mL – 61 mL = 189 mL H 2 O 2. (14 points) (1 point each, no partial credit) Fill in the following blanks with the single-letter code for the amino acid that best fits the description: __S___ Plays the role of the initiating nucleophile during peptide bond cleavage catalyzed by the catalytic triad of chymotrypsin __M___ Cyanogen bromide cleaves polypeptides on the C-terminal side of this amino acid __K___ In addition to R and H, this amino acid is positively charged at neutral pH __W___ In addition to Y, proteins containing this amino acid absorb 280 nm light __G___ In addition to P and 4-hydroxy-P, this amino acid is common in collagen __P___
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern