2008mcb2014f - University of Cape Town Department of...

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University of Cape Town Course Code: MCB2014F Course Name: Molecular Components of Cells Paper: 1 (Theory) Date: 5 June 2008 No.of pages: 11 Marks: 120 Time: 3 Hours Venue: LS 2A Attachment: 2 pages data sheet Time: 08h00 ANSWER ALL THE QUESTIONS In the interest of economy please write on both sides of the exam script Please answer each section in a different answer book. Multiple choice questions will be subjected to negative marking Section 1: Dr Jerry Rodrigues 60 Marks (A) Buffers, thermodynamics etc (5 marks) The following questions (1 to 5) are of the multiple choice type – provide the most appropriate answer: 1. Which one of the following statements about the structure of ATP is correct? (A) It contains three phosphoanhydride bonds. (B) It contains two phosphate ester bonds. (C) The sugar moiety is linked to the triphosphate by a phosphoanhydride bond. (D) The nitrogenous base is called adenosine . (E) The active form is usually in a complex with Mg 2+ or Mn 2+ (1) 2. Which of the following are high-energy compounds? (A) Glycerol 3-phosphate (B) Adenosine monophosphate (AMP) (C) Glucose 1-phosphate (D) Acetyl phosphate (E) Fructose 6-phosphate (1) 3. If equal amounts of H 3 PO 4 and NaH 2 PO 4 are mixed in water, calculate the resulting pH. The pK a s of phosphoric acid are 2.1, 7.2 and 12.4. (A) 2.1 (B) 4.5 (C) 7.2 (D) 9.8 (E) 12.4 (1) 4. All of the statements about the nature of the hydrogen bond are true EXCEPT: (A) The donor is a hydrogen atom bonded to a carbon. (B) The more linear the bond, the stronger the interaction. (C) The acceptor is a weakly electronegative atom containing a nonbonding pair of electrons. (D) It is a type of non-covalent bond. (E) A hydrogen bond is stronger than van der Waals forces. (1) 1
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5. In micelles: (A) polar ends form hydrophobic interactions with water. (B) nonpolar ends form hydrophilic interactions with water. (C) hydrocarbon tails form hydrophobic interactions with water. (D) polar ends are hydrophobic and nonpolar ends are hydrophilic. (E) hydrocarbon tails are excluded from the water into hydrophobic domains. (1) (B) Amino acids and proteins (40 marks) 6. Given a nonapeptide with the following amino acid sequence, Val-His-Ser-Ile-Phe-Arg-Cys-Tyr-Leu (a) Identify the charged groups in the peptide shown above, at pH = 1 and at pH = 7. (3) (b) What is the nett charge of this polypeptide at these two pH values? (2) 7. What is the stereochemical basis of the observation that D-aspartyl-D-phenylalanine has a bitter taste whereas L-aspartyl-L-phenylalanine (Aspartame™) is significantly sweeter than sugar? (2) 8. Draw the structure of histamine, an important biologically active derivative of the amino acid histidine, often involved in allergic reactions in the body. (2) 9. Histidine has three ionizable functional groups. (a)
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This note was uploaded on 01/05/2011 for the course BLY 440 taught by Professor Williams during the Fall '10 term at Alabama.

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2008mcb2014f - University of Cape Town Department of...

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