assignment 1 pi concept - triyambak.orgtriyambak.org/study-material/1.pdf · earth to the moon...

1. If you were to magnify a cell 10,000-fold (typical of the magnification achieved using an electron microscope), how big would it appear? Assume you are viewing a “typical” eukaryotic cell with a cellular diameter of 50 mm.

A. 500 MM B. 400 mm C. 450 mm D. 50 mm

2. If this cell were a muscle cell (myocyte), how many molecules of actin could it hold? (Assume the cell is spherical and no other cellular components are present; actin molecules are spherical, with a diameter of 3.6 nm.

A. 2.7 x 1026 B. 2.4 x 1021 C. 2.7 x 1022 D. 2.7 x 1012

3. If this were a liver cell (hepatocyte) of the same dimensions, how many mitochondria could it hold? (Assume the cell is spherical; no other cellular components are present; and the mitochondria are spherical, with a diameter of 1.5 mm.)

A. 3.6 x 104 B. 3.6 x 105 C. 3.6 x 107 D. 3.6 x 106

4. Glucose is the major energy-yielding nutrient for most cells. Assuming a cellular concentration of 1 mM, calculate how many molecules of glucose would be present in our hypothetical (and spherical) eukaryotic cell.

A. 3.9 x 1017 B. 3.6 x 1014 C. 39 x 109 D. 3.6 x 1014

5. Hexokinase is an important enzyme in the metabolism of glucose. If the concentration of hexokinase in our eukaryotic cell is 20 mM, how many glucose molecules are present per hexokinase molecule?

A. 150 B. 500 C. 50 D. 30

6. E. coli cells are rod-shaped, about 2 mm long and 0.8 mm in diameter. The volume of a cylinder is πr2h, where h is the height of the cylinder. If the average density of E. coli (mostly water) is 1.1 x 103 g/L, what is the mass of a single cell?

A. 1 pg B. 1 ng C. 1 fg D. 1 µg

7. Using Information from previous question, E. coli has a protective cell envelope 10 nm thick. What percentage of the total volume of the bacterium does the cell envelope occupy?

A. 78% B. 90% C. 56% D. 69%

8. E. coli is capable of growing and multiplying rapidly because it contains some 15,000 spherical ribosomes (diameter 18 nm), which carry out protein synthesis. What percentage of the cell volume do the ribosomes occupy?

A. 14% B. 50% C. 5% D. 15%

9. The genetic information contained in DNA consists of a linear sequence of coding units, known as codons. Each codon is a specific sequence of three deoxyribonucleotides (three deoxyribonucleotide pairs in double-stranded DNA), and each codon codes for a single amino acid unit in a protein . The molecular weight of an E. coli DNA molecule is about 3.1 x 109 g/mol. The average molecular weight of a nucleotide pair is 660 g/mol, and each nucleotide pair contributes 0.34 nm to the length of DNA. Calculate the length of an E. coli DNA molecule. Compare the length of the DNA molecule with the cell dimensions (E. coli cells are rod-shaped, about 2 mm long and 0.8 mm in diameter). How does the DNA molecule fit into the cell.

A. 1.6 nm B. 1.6 MM C. 2.1 nm D. 2.1 mm

10. From the previous question, assume that the average protein in E. coli consists of a chain of 400 amino acids. What is the maximum number of proteins that can be coded by an E. coli DNA molecule?

A. 40000 B. 4000000 C. 400 D. 400000

11. Calculate the surface-to-volume ratio for the spherical bacterium Neisseria gonorrhoeae (diameter 0.5 mm), responsible for the disease gonorrhea. Compare it with

Assignment 1 pI concept

Triyambak Life Science 1

the surface-to-volume ratio for a globular amoeba, a large eukaryotic cell (diameter 150 mm). The surface area of a sphere is 4πr2.

A. surface-to-volume ratio is 300 times lesser for the bacterium

B. Surface-to-volume ratio is 300 times greater for the bacterium

C. surface-to-volume ratio is 50 times greater for the bacterium

D. surface-to-volume ratio is 50 lesser greater for the bacterium

12. Bacterial cells have a much higher rate of metabolism than animal cells. Under ideal conditions some bacteria double in size and divide every 20 min, whereas most animal cells under rapid growth conditions require 24 hours. The high rate of bacterial metabolism requires a high ratio of surface area to cell volume. Which statement is true regarding Surface to Volume ratios?

A. As the ratio of surface area to volume increase, the rate of diffusion cannot keep up with the rate of metabolism within the cell.

B. As the ratio of surface area to volume decreases, the rate of diffusion cannot keep up with the rate of metabolism within the cell.

C. As the ratio of surface area to volume decreases, the rate of diffusion can keep up with the rate of metabolism within the cell.

D. No effect on the rate of diffusion

13. If the average velocity of a vesicle is 1 mm/s, how long does it take a vesicle to move from a cell body in the spinal cord to the axonal tip in the toes (suppose length of axon is about 2 m)?

A. 23 sec. B. 23 min. C. 23 hr. D.23 days

14. An unknown substance, X, was isolated from rabbit muscle. Its structure was determined from the following observations and experiments. Qualitative analysis showed that X was composed entirely of C, H, and O. A weighed sample of X was completely oxidized, and the H2O and CO2 produced were measured; this quantitative analysis revealed that X contained 40.00% C, 6.71% H, and 53.29% O by weight. The molecular mass of X, determined by mass spectrometry, was 90.00 u. Infrared spectroscopy showed that X contained one double bond. X dissolved readily in water to give an acidic solution; the solution demonstrated optical activity when tested in a polarimeter. The empirical formula, molecular formula and possible structures of X will be

A. C2H2O, CH6O3, 14 B. C2HO, C4H6O3, 12

C. CH2O, C3H6O3, 12 D. C4H2O, C3H8O3, 14

15. A quantitative amino acid analysis reveals that bovine serum albumin (BSA) contains 0.58% tryptophan (Mr 204) by weight. What should be the minimum molecular weight of BSA (i.e., assuming there is only one tryptophan residue per protein molecule).

A. 64 kDa B. 32 kDa C. 12 kDa D. 90 kDa

16. A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein gives three bands with molecular masses of 180, 160, and 60 kDa. When electrophoresis is carried out in the presence of SDS and dithiothreitol, three bands are again formed, this time with molecular masses of 160, 90, and 60 kDa. Subunit in the protein is/are

A. 3 B. 4 C. 6 D. 1

17. A peptide has the sequence Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly. What should be the net charge of the molecule at pH 3, 8, and 11

A. +1, 0, +1 B. +2, 0, -2 C. +2, 0, -3 d. +2, 0, - 1



18. Which of the polypeptide will be most soluble at the pH 7?

A. (Glu)20 B. (Phe-Ala)10 C. (Met-Ala)10 D. (Leu-Val)20

19. How many ionisable groups a Histidine has

A. 2 b. 3 C. 4 D. 1

20. What should be the charge on Histidine at pH 1, 4, 8, 12

A. 2, 1, 0, 1 B. 2, 1, 0, -3 C. 2, 1, 0, -2 D. 1, 2, 0, -3

21. Hair grows at a rate of 15 to 20 cm/yr. Calculate the rate at which peptide bonds of a-keratin chains must be synthesized (peptide bonds per second) to account for the observed yearly growth of hair.

A. 34 B. 42 C. 60 D. 20

22. Which is the correct explanation for the effect of the pH changes on the conformations of poly(Glu) and poly(Lys)

A. repulsion maximised at pH 1 and pH 12 for Lys and Glu

B. repulsion maximised at pH 1 and pH 12 for Glu and Lys

C. No repulsion at pH 1 and pH 12 for Lys and Glu

D. repulsion minimised at pH 1 and pH 12 for Lys and Glu

23. Where might bends or β turns occur?

A. 7 and 19 B. 10 and 15 C. 7 and 12 D. 3 and 19

24. X-ray analysis of Bacteriorhodopsin membrane protein (Mr 26,000) protein reveals that it consists of seven parallel a-helical segments, each of which traverses the bacterial cell membrane (thickness 45 Å). What shouldbe the minimum number of amino acids necessary for one segment of a helix to traverse the membrane completely and the fraction of the bacteriorhodopsin protein that is involved in membrane-spanning helices.

A. 50 amino acid residues and 47% B. 30 amino acid residues and 87%

C. 12 amino acid residues and 13% D. 18 amino acid residues and 87%

25. Calculate the weight in grams of a double-helical DNA molecule stretching from the Earth to the moon (~320,000 km). The DNA double helix weighs about 1 x10-18 g per 1,000 nucleotide pairs; each base pair extends 3.4 Å. For an interesting comparison, your body contains about 0.5 g of DNA.

A. 0.0014g B. 0.094g C. 0.00094g D. 0.194g



26. Assume that a poly(A) tract five base pairs long produces a 20o bend in a DNA strand. Calculate the total (net) bend produced in a DNA if the center base pairs (the third of five) of two successive (dA)5 tracts are located 10 base pairs apart.

A. 25o B. 30o C. 560 D. 40o

27. The carbon–carbon bond distance for single-bonded carbons such as those in a saturated fatty acyl chain is about 1.5 Å. Estimate the length of a single molecule of palmitate in its fully extended form. If two molecules of palmitate were placed end to end, how would their total length compare with the thickness of the lipid bilayer in a biological membrane.

A. 4 nm B. 10 mm C. 12 nm D. 11 nm

28. Which of the following amino acids strongly absorbs UV light?

A. W B. Y C. F D. all of the above

29. The net charge on the amino acid lysine at pH 7.4 is

A. +2 B. -1 C. +1 D. -2

30. Which of the following amino acids is likely to be found on the surface of a globular protein?

A. alanine B. leucine C. isoleucine D. serine

31. Which of the following is derived from the amino acid glutamate?

A. gamma-aminobutyrate B. triiodothyronine

C. epinephrine D. histamine

32. Which of the following forms of cysteine predominates at pH 9?

A. B. C. D.

33. Which of the following amino acids are capable of forming a homodimer in proteins when oxidized?

A. B. C. D.

34. Of the following tripeptides, which is more likely to be soluble in a nonpolar solvent?

A. lysylglycylserine B. leucylalanyltrypthophan

C. threonylleucylhistidine D. valyltryptophanylglutamine

35. The form of aspartate depicted below predominates at which point on the titration curve?



A. A B. B C. C D. D E. E F.F

36. Although protein concentration can be estimated by measuring the absorbance of a protein solution at 280 nm, this technique does not yield an accurate measure of absolute protein concentration. Why?

A. Proteins scatter light optimally at this wavelength, thus interfering with the concentration measurement.

B. Protein solutions refract light optimally at 280 nm, thus interfering with the measurement.

C. Cysteine residues absorb light optimally at this wavelength.

D. Most proteins contain strongly attached chromophore molecules, such as hemes, that absorb light at 280 nm.

37. Calculate the net charge of the following decapeptide at neutral pH: MARLYWEQCK

A. 1 B. 2 C. -2 D. -1

38. Free rotation about the peptide bond in a protein is restricted primarily because of

A. partial double-bond character of the peptide bond.

B. hydrogen bonding to the amide backbone groups.

C. partial double-bond character of the N-Calpha bond.

D. restrictions caused by local folding patterns.

39. Proline has a limited number of allowed conformations because

A. the side chain is linked to the alpha amino group.

B. it has a bulky side chain.

C. it is a small aliphatic amino acid.

D. its side chain is uncharged.

40. The translational length/amino acid in an alpha-helix, 310 and pi helix are as

A. 1.1, 2.0, 1.5 B. 2.0, 1.3, 1.5

C. 1.5, 2.0, 1.1 D. 1.1, 2.0, 1.5

41. Which of the following is a representation of a Schiff base?

A. B. C. D.

42. Which of the following statements most accurately describes the conclusions of Christian Anfinsen's experiment with ribonuclease A?

A. The primary amino acid sequence of ribonuclease is the primary determinant of its three-dimensional structure.



B. Denaturants, such as urea, are sufficient to completely denature ribonuclease.

C. Disulfide bridging occurs only when proteins are properly folded.

D. Enzyme activity is preserved even when the protein is denatured.

43. Complete reduction of the disulfide bonds of immunoglobulin G yields how many different polypeptide chains?

A. 1 B. 2 C. 3 D. 4

44. The predominant secondary structural motif in an antibody molecule is

A. antiparallel beta-sheet B. a 4-helix bundle

C. alpha-helical coiled coil D. alpha-helix

45. Inter-strand hydrogen bonds to the main-chain amide bonds help to stabilize the secondary structure of

A. beta-sheets B. a 310 helix. C. a 313 helix. D. beta turns.

46. In an alpha helix, the amide carbonyl oxygen of an amino acid residue n is hydrogen-bonded to the amide hydrogen of residue n + _?

A. 2 B. 3 C. 4 D. 5

47. Which of the following amino acids is least likely to be found in an extended alpha-helix?

A. proline B. arginine C. asparagine D. isoleucine

48. A Greek key is

A. a supersecondary protein structure composed of antiparallel beta-sheets.

B. a supersecondary protein structure composed of parallel beta-sheets.

C. a Type I turn. D. a Type II turn.

49. What is the force that is primarily responsible for stabilizing the tertiary structure of globular proteins?

A. the hydrophobic effect B. disulfide bonding

C. hydrogen bonding D. ionic interactions

50. Which of the following proteins stabilize unfolded proteins?

A. chaperones B. lactalbumin C. lysyl oxidase D. PPI

51. Substitution of Gly in the primary sequence of collagen with almost any other amino acid results in defective collagen assembly because

A. the contact points of the triple helix are so close that only the Gly side chain fits well into the space available.

B. collagen is glycosylated on Gly residues.

C. Gly forms critical hydrogen bonds with neighboring glycines.

D. Gly is crosslinked to allysine residues in the mature protein.

52. A Ramachandran plot describes, for a particular amino acid, the sterically permitted angles for

A. rotation about the Calpha-Cbeta bond. B. rotation about the Calpha-C bond.

C. rotation about the N-Calpha bond. D. both B and C

53. Which of the following peptides is likely to form an amphipathic helix?

A. phe-asp-arg-gly-leu-glu-ile-ile-lys-ser-gly



B. arg-asp-ser-gly-phe-leu-ile-ile-gly-glu-lys

C. phe-asp-gly-arg-leu-glu-ile-lys-ile-ser-gly

D. phe-gly-leu-ile-asp-arg-glu-lys-ile-ser-gly

54. Isolated beta-strands in proteins are rare primarily because

A. adjacent beta-strands are required to satisfy the hydrogen bond requirement of the main-chain amide bonds.

B. beta-strands always prefer to be buried in the interior of proteins.

C. most amino acids prefer the alpha-helix conformation.

D. Polypeptide chains do not prefer to adopt an extended conformation.

55. Antiparallel beta-sheets are often found at the surface of a protein, while parallel beta-sheet structures are found in the interior of proteins. From this information, one can infer that

A. antiparallel beta sheets are composed of alternating hydrophobic and hydrophilic amino acids.

B. anti-parallel beta sheets are composed of hydrophilic amino acids only.

C. every third or fourth amino acid in an antiparallel beta sheet is charged.

D. Parallel beta sheets contain alternating hydrophilic and hydrophobic amino acids.

56. Which of the following statements about multisubunit globular proteins is incorrect?

A. Subunits are typically held together by covalent interactions.

B. Errors during protein synthesis are minimized by the synthesis of shorter proteins.

C. Multisubunit enzymes often assemble the active site with residues from adjacent subunits.

D. Multisubunit proteins are typically regulated by ligand-induced changes in monomer subunit structure.

57. The formation of an alpha helix results in a dipole along the helix, with a positive N-terminus and a negative C-terminus. What is the most likely explanation for this phenomenon?

A. The helix dipole is the sum of each peptide bond dipole moment.

B. the N-terminus of a protein contains a positively charged amine group, while the C-terminus contains a negatively charged carboxl group.

C. the peptide carbonyl oxygens that hydrogen bond with amide hydrogens "point" toward the C-terminus.

D. Side chain residues in alpha helices extend outward, perpendicular to the axis of the helix.

58. The role of molecular chaperones in protein folding is to:

A. increase the rate of folding into the correct conformation by binding to newly synthesized, unfolded proteins.

B. recognize, bind, and unfold incorrectly folded proteins, thus allowing them to refold properly.

C. modifiy side chain residues in newly synthesized proteins in order to prevent interactions that could lead to misfolding

D. reduce incorrectly formed disulfide bridges that can lead to misfolding.



59. You discover a fibroblast cell line that produces defective collagen. The collagen that this cell line synthesizes does not forms a triple helix and no collagen is secreted. Which of the following might explain this mutation?

A. The collagen has an Gly->Arg mutation.

B. A defect is present in prolyl or lysyl hydroxylase.

C. A defect in lysyl oxidase.

D. A defect in vitamin C uptake.



assignment 1 pi concept - triyambak.orgtriyambak.org/study-material/1.pdf · earth to the moon...

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