2005mcb201s

2005mcb201s - University of Cape Town Department of...

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University of Cape Town Course Code: MCB201S Physiological Biochemistry Paper: 1 Date: 31 October 2005 No.of pages: 12 Marks: 129 Time: 3 Hours Venue: DO1 Time: 14h00 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. Section 1 : Dr Jerry Rodrigues 98 Marks Carbohydrates: (17 marks) The following questions (1 to 10) are of the multiple choice type (give best answer) 1. Consider the sugars shown below: Answer the following three questions about these carbohydrate structures. -What kind of isomers are A and B? -What kind of isomers are A and C? -What kind of isomers are B and C? a. anomers; epimers; enantiomers b. enantiomers; anomers; diastereomers c. diastereomers; enantiomers; epimers d. epimers; enantiomers; diastereomers e. enantiomers; epimers; anomers (3) 2. β -D-glucopyranose in the chair form is the most widely occurring form of glucose in nature and it has the following characteristics EXCEPT: a. forms a six-membered ring. b. carbon 6 is above the plane of the chair. c. all of the -OH groups are equatorial. d. the anomeric carbon has a hydroxyl that is below the plane of the chair. e. all axial positions are occupied by -H. (1) 1
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"Blood sugar" in hemolymph of insects is trehalose, represented as _____________. a. α Glc(1→1) α Glc b. α Glc c. α Glc(1→ 4) β Glc d. β Gal(1→ 4) α Glc e. β Glc(1→ 4) β Glc (1) 4. In plant cells, starch is hydrolyzed by _________________ to release _________________ and a starch molecule with ________________. a. starch phosphorylase; glucose-1-phosphate; one less glucose unit b. salivary α -amylase; maltose 1-phosphate; two less glucose units c. starch phosphorylase; maltose 1-phosphate; two less glucose units d. α (1 6) glucosidase; glucose-6-phosphate; one less glucose unit e. starch hydrolase; glucose; one less glucose unit (1) 5. Cooked starch is more digestible because: a. it has been partially hydrolyzed during cooking. b. the amylopectin is converted to amylose during cooking. c. the enzymes that hydrolyze the starch are only active when the starch is hot. d. the starch granules take up water, swell and are more accessible to the enzymes. e. all are true. (1) 6. Which of the following statements about cellulose fiber is true? a. It is a linear polymer of β (1 4) glycosidic linked glucose and galactose residues. b. It is extremely susceptible to hydrolysis. c. It is water-soluble. d. It is made up of very weak microfibrils. e. Intermolecular hydrogen bonds play a major role in stabilization of the microfibrils. (1) 7. Cellulose is extremely resistant to hydrolysis, but cellulase catalyzes the hydrolysis and comes from: a. the pancreas. b.
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2005mcb201s - University of Cape Town Department of...

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