2001mcb200f1 - University of Cape Town Department of...

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University of Cape Town MCB200F : Introduction to Biochemistry Paper 1 June 2001 Time: 3 hours Marks: 89 ANSWER ALL THE QUESTIONS In the interest of economy please write on both sides of the exam script Please answer each lecturer’s questions in a different answer book. Graph paper will be provided. Section 1 J Rodrigues (20 Marks) 1. What is the molarity of pure ethanol, i.e. how many moles of ethanol are present in 1 litre (L) of pure ethanol? The density of ethanol is 0.8 g/mL. MW: 46 (2) 2. Bovine serum albumin (BSA) was used to draw up a standard curve for the spectrophotometric determination of protein (Biuret method). The data obtained were as follows: Absorbance (OD) mg BSA/10 mL 0.103 4.5 0.210 9.0 0.289 13.5 0.390 18.0 0.505 22.5 0.551 27.0 0.590 31.5 0.611 36.0 (a) Plot the standard curve (4) (b) Indicate up to which OD level this method can be considered to obey the Beer-Lambert Law. (1) (c) State the mathematical relationship that describes the linear portion of this graph. (2) (d) Derive the slope: now using the slope, calculate the concentration in an unknown protein sample with an OD = 0.2287. (3) 3. The peptide hormone ‘vasopressin’ is used in the regulation of saltwater balance in many vertebrates. Porcine (pig) vasopressin has the sequence: Asp-Tyr-Phe-Glu-Asn-Cys-Pro-Lys-Gly MW: 1072 (a) Using the data in Fig 1 (below), estimate the extinction coefficient (molar
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2001mcb200f1 - University of Cape Town Department of...

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