Q1: Circle the best correct answer: (15 marks)

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1 Q1: Circle the best correct answer: (15 marks) 1. Which one of the following incorrectly pairs an amino acid with a valid chemical characteristic a. Glycine, is chiral b. Tyrosine and tryptophan; at neutral ph absorb light strongly at 280nm c. Serine, is amino acid contains alcohol groups d. Histidine: has an Imidazole group 2. Proteins contain: a. Only L-amino acids b. Only D-amino acids c. DL-Amino acids d. Both (a) and (b) 3. Cystine contain disulfide a ( CH2 S S CH2 ) bond is synthesized from: a. Arginine b. Methionine c. Cysteine d. Leucine 4. Which of the following statements about haemoglobin A are incorrect? a. Two α and two β chains, held together by non-covalent interactions b. binding of oxygen to haemoglobin considered allosteric effect c. haemoglobin has sigmoidal Oxygen dissociation curve d. haemoglobin has only one form; (taut)t 5. Which of the following statements about β-turn are incorrect? a. stabilize only by hydrogen b. found on the surface of protein c. β-bends reverse the direction of a polypeptide chain d. Proline and Glycine also found in β-turn 6. Which of the following statements about α-helix are correct? a. Spiral, packed and coiled b. R extending outside of the helix spiral c. Stabilize by hydrogen bond 7. The Ip of Glutamate (glutamic acid) is: a b c d

2 8. During denaturation of proteins, all of the following are disrupted except: a. Primary structure b. Secondary structure c. Tertiary structure d. Quaternary structure 9. α-helix is disrupted by all except: a. proline b. alanine c. Leucine and tryptophan d. electrostatic repulsion between charged amino acids 10. Which of the following is not true concerning collagen? a. Collagen is most abundant protein in mammals b. It is found in connective tissue such tendons and cartilage c. an example of collagen disease is Ehlers-Danlos syndrome (EDS) d. Collagen is rubber like structure 11. Folding process required: a. chaperones bind hydrophobic region b. adenosine triphosphate hydrolysis c. denaturation agent and prion d. Both a and b 12. The peptide valylglutamyltyrosylleucine has: a. disulfide bridge b. Three peptide bonds c. Four peptide bonds d. Two N-terminal 13. Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called: a. primary structure b. secondary structure c. tertiary structure d. quaternary structure 14. hemoglobin can transfer: a. Three molecule of oxygen b. One molecule of oxygen c. Four Three molecule of oxygen d. One atom of oxygen 15. The core of a domain is built from combinations of: a. α-helix b. β-bends c. supersecondary α-sheet d. β-sheet 16. An example of polar amino acid is a. Alanin b. Tryptophan c. Arginine d. Valine 2

3 17. Which is correct about myoglobin? a. has higher affinity for O2 than haemoglobin b. composed from eight stretches of α-helix which terminated by proline. c. Have hyperbolic curve 18. The factors that cause Alzheimer disease in humans: a. aggregate of abnormal prion b. Accumulation of (Aβ) and neurofibrillary tangles in brain c. virus infection d. Bacterial infection 19. Tertiary structure is stabilized by: a. Hydrogen bonds and ionic bond b. Disulphide bonds c. Hydrophobic interactions 20. When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe 2+ are occupied by: a. One O atom and one histidine b. One O 2 molecule and one heme group c. One O 2 molecule and one histidine d. Two O 2 molecules Amino acid that has sulfur and the first amino acid in a polypeptide chain is: a. Glycine b. Methionine c. Valine d. Asparagine 22. Which of the following statements is incorrect concerning Elastin? a. Synthesized from tropoelastin, small non polar amino acids b. Mutations in fibrillin gene are responsible for Marfins syndrome c. Genetic defects in α-1antitrypsin can lead to emphysema d. Elastin is an example of globular protein 23. Which of the following is incorrect in collagen synthesis? a. Transcription of collagen α-chain gene b. Translation into polypeptide c. Glycosylation of hydroxylysine d. fibril collagen held by desmosin link 24. Which is incorrect about the peptide bond? a. partial double bond b. rigid and planar c. Ionization at physiological ph d. trans configuration 25. An example of polar amino acid is a. Alanine b. Arginine c. tryptophan d. Valine 3

4 26. The reason of the major β-thalasemia is: a. defect only on one β-globin b. defect only on one α-globin c. defect only on two β-globin d. defect only on four α-globin 28. Isoleucine; is non-polar and found: a. on the surface of protein b. in buried in the centre of proteins c. not included in proteins d.all of these 29. Which of the following is required for cross linking of collagen? a. lysyl oxidase enzyme d. glycosylation of hydroxyproline c. prcollagen peptidase d. Pro hydroxylase enzyme 30. Mutations in two β-globin gene, at position six the glutamate converts to valine cause the: a. Hb C disease b. Hb S disease (sickle cell) c. β- Thalassemias d. α- Thalassemias Q2. Write true or false : (3 marks) 1. Glycine contains the smallest side chain ( ). 2. Proline is the cyclic amino acid so can form kink ( ). 3. Histidine contains a guanidino group ( ). 4. Isoleucine and threonine have one chiral carbon ( ). Q3. Name the following amino acids, and give its triple letter abbreviation, and indicate whether it is polar, and non-polar: (1 mark) a) b) a). b) 4

5 Q4. Write short note: (2 marks) 1. Explain, the primary structure of proteins are not denatured. 2. Explain, Hemoglobin C disease migrates to the negative electrode in electrophoresis. 3. Explain, Hydroxyproline is important in stabilizing the triple-helical structure of collagen. Good luck 5