Biology 263 Cell Biology
Dr. Joel B. Piperberg December 17, 2009
Final Exam Name ______Page #15
I. Multiple Choice. Fill in the best answer on the answer sheet.
1. What is the name given to carbohydrates bound to serine or threonine residues on a secretory protein?
a. N-linked carbohydrates b. O-linked carbohydrates c. proteoglycans d. glycoproteins e. a and b
2. What controls the sequence of carbohydrates on oligosaccharides attached to secretory proteins?
a. whatever carbohydrates are close to the proteins
b. the sequence of galactose oxidases in the RER and SER
c. the arrangement and sequence of glycosyltransferases in the RER, SER and Golgi apparatus
d. the sequence of nucleotides in the nucleotide sugars
e. b and c
3. ______attach cells to ______.
a. Hemidesmosomes, a noncellular surface c. Maculae adherens, neighboring cells e. a, b and c
b. Zonulae adherens, neighboring cells d. Zonulae adherens, a noncellular surface
4. What is the name of the cytoskeletal element associated with maculae adherens?
a. keratin b. microfilaments c. tubulin d. a and e e. tonofilaments
5. You mix secretory and domestic protein mRNA, ribosomes, naked RER vesicles that have been stripped of their ribosomes and everything else you need to synthesize proteins in a test tube and let them incubate for 30 minutes. After the incubation, what do you find in the test tube?
a. domestic proteins floating free in the buffer in the test tube
b. secretory proteins inside RER vesicles with ribosomes bound to their inner surface
c. secretory proteins inside RER vesicles with ribosomes bound to their outer surface
d. domestic proteins in the RER vesicles with ribosomes bound to their inner surface
e. a and c
6. Which cell junction below may attach epithelial cells to each other and are built to withstand a great deal of force in holding cells together?
a. zonulae occludens b. maculae adherens c. zonulae adherens d. belt desmosomes e. b, c and d
7. What changes can be made in a secretory protein after it has already entered the RER?
a. addition of new amino acids to the signal sequence d. b and c
b. addition of a segment of the amino acids to the interior of the secretory protein e. a, b and c
c. addition of sugars to the carbohydrates donated to the protein by dolichol phosphate
8. Which cell adhesion molecules that bind to specific carbohydrates on the cell surface are named after a group of plant molecules that are known for their ability to bind specific carbohydrates?
a. selectins b. lectins c. IgSFs d. integrins e. cadherins
9. What cell junction(s) is (are) responsible for preventing materials from getting past an epithelium like the urinary bladder epithelium? It does so by preventing these materials from moving between epithelial cells.
a. gap junctions b. gapulae adherens c. maculae adherens d. tight junctions e. c and d
10. Which enzyme would be most likely to be located in a peroxisome?
a. RNase b. amino acid oxidase c. b and d d. catalase e. acid phosphatase
11. In which organelle would most secretory proteins receive their first glycosylation?
a. RER b. secretory vesicles c. Golgi apparatus d. SER e. a and d
12. A pulse-chase experiment is carried out by exposing rat parotid cells to radioactive glycerol for a brief period of time followed by increasing chase periods in the presence of unlabeled glycerol precursors? What is the most important revelation of this technique?
a. the time it takes to synthesize a single membrane lipid
b. the pathway membrane lipids follow through the cell on their way to the membrane
c. the time it takes for a secretory protein to be secreted
d. the pathway membrane proteins follow through the cell on their way to the membrane
e. c and d
13. Which organelle is most prominent in the photosynthetic tissues of plants?
a. peroxisomes b. lysosomes c. glyoxysomes d. contractile ring e. centrioles
14. You mix radiolabeled mouse liver cells with a number of different cell types, each grown to cover separate Petri dishes. The radiolabeled cells are most likely to adhere to which cell type below?
a. mouse liver b. rat liver c. a and e d. a and b e. mouse retina
15. What may account for differences in the appearance of RER and SER?
a. the presence of ribosomes on the RER d. the distribution of ribosome docking proteins (translocons)
b. the relative amounts of certain enzymes e. a, b and d
c. the relative amounts of certain nucleic acids
16. The mRNA for a well-known secretory protein is isolated and placed in a test tube in the presence of all the substances required for in vitro protein synthesis. The sequence of the protein produced in vitro is then compared to the sequence of the purified secretory protein from the cell. The amino acid sequences of the two proteins are not the same. What is the explanation?
a. A short chain of mostly hydrophobic amino acids was removed from the C-terminal end of the polypeptide in the test tube before it was analyzed.
b. A short chain of mostly hydrophilic amino acids was chopped off the N-terminal end of the protein purified from the secretory cell.
c. The mRNA was cleaved after being translated in the test tube,
d. A largely hydrophobic segment at the N-terminal end of the polypeptide is cut off of a protein synthesized in vitro (in the test tube) and degraded by the signal peptidase.
e. none of the above
17. Dolichol phosphate ______.
a. is a phosphatidyl protein
b. donates a block of carbohydrates to proteins destined for the cell membrane as they project through the RER membrane
c. is a membrane phospholipid
d. and its attached carbohydrates flip from the membrane leaflet facing the RER lumen to the cytoplasmic leaflet
e. b and c
18. Which enzyme would be most likely to be found in a lysosome?
a. b and d b. acid phosphatase c. catalase d. hexosaminidase e. amino acid oxidase
19. Which organelle is observable only in an animal cell?
a. mitochondria b. vacuole c. glyoxysome d. peroxisome e. none of the above
20. Storage diseases like Hurler's syndrome and Tay-Sachs disease may result from ______enzymes.
a. nonfunctional peroxisomal c. nonfunctional lysosomal e. c and d
b. missing mitochondrial d. overabundant lysosomal
21. Which name below would be the name of an enzyme in the RER, SER or Golgi apparatus that is responsible for adding sugars to growing oligosaccharide chains attached to the proteins passing through them?
a. glucosyltransferase c. peptidylsynthase e. glycosylsynthetase
b. a and d d. glycosyltransferase
22. Which of the following molecules has been reduced by binding to high-energy electrons?
a. ATP b. FADre c. FADox d. NADre e. b and d
23. You are studying some photosynthetic bacteria found in the sulfur pools of Yellowstone Park. They contain only one photosystem and yet seem to be able to carry out both cyclic and non-cyclic photophosphorylation. The sulfur in the pools is found in various forms including hydrogen sulfide (H2S), an electron-rich compound. How could the bacteria carry on photosynthesis with just one photosystem?
a. none of the other answers
b. They acquire electrons from water to replace those stored in NADPox.
c. They acquire electrons from water to replace those stored in NADre.
d. They acquire electrons from hydrogen sulfide to replace those stored in NADPox.
e. They make ATP whether they are carrying on respiration or non-cyclic photophosphorylation.
24. In what part of the cell can lysosomes form?
a. b, c and d c. GERL e. c and d
b. rough endoplasmic reticulum d. in the Golgi apparatus
25. Fibronectin is likely to have binding sites for which of the following molecules?
a. cell surface proteins b. collagen c. tubulin d. GAGs e. a, b and d
26. Which word or words below is associated with a receptor tyrosine kinase?
a. insulin b. serine c. cAMP d. transautophosphorylation e. a and d
27. What second messenger appears to be responsible for relieving the pain of angina?
a. carbon monoxide b. nitrous oxide c. monoamine oxidase d. NO e. b and d
28. The cell coat is composed of ______.
a. carbohydrates attached by covalent bonds to membrane proteins d. a and b
b. carbohydrates attached noncovalently to transmembrane proteins e. a, b and c
c. the glycocalyx and the fuzzy layer
29. The function of the glycocalyx is ______.
a. to generate friction between neighboring cells d. b, c and e
b. to mediate interactions between cells e. to act as a molecular sieve
c. to prevent large molecules from getting to the cell membrane
30. Radiolabeled monosaccharides are given to growing secretory cells. Over which of the following structures would silver grains first appear?
a. rough ER b. Golgi apparatus c. secretory vesicles d. a and e e. smooth ER
31. Patients with I-cell disease ______
a. may make excess receptors for mannose-6-phosphate in carbohydrates attached to lysosomal enzymes
b. may be unable to add phosphate groups to mannose residues in the carbohydrates of lysosomal enzymes
c. synthesize peroxisomal enzymes without properly marking them as such
d. are unable to place lysosomal enzymes effectively within lysosomes
e. b and d
32. What characteristics of the signal peptide allow it to penetrate the RER membrane easily?
a. It is 15 - 30 amino acids long. d. It is mostly made up of hydrophilic amino acids.
b. Its sequence is recognized by the GERL. e. c and d
c. Its central 9 - 12 amino acids are primarily hydrophobic.
33. Which of the following is a function of the rough endoplasmic reticulum?
a. It adds sugars to carbohydrate chains on presumptive membrane proteins.
b. It can excise amino acid segments from proteins.
c. It synthesizes domestic proteins.
d. It synthesizes secretory proteins.
e. a and d
34. According to chemiosmosis, the energy stored in ATP by mitochondrial electron transport is generated when ______.
a. ATP synthetase produces NADPre in addition to ATP
b. electron transport drives a transmembrane H+ ion pump that establishes a steep H+ ion gradient
c. electrons are transported hyperkinetically
d. energy is stored in an electrochemical gradient between the thylakoid disk lumen and the stroma
e. b and d
35. You are conducting an experiment in photosynthesis. You have radioactively labeled the oxygen in a compound and have observed that this oxygen is soon seen in the carbohydrates of the plant. What compound was labeled?
a. water b. carbon monoxide c. starch d. carbon dioxide e. glucose
36. Some of the molecules of the electron transport chain in chloroplasts accept electrons while others accept electrons and hydrogen ions. This is significant because ______.
a. it explains how these molecules can transport protons for the purpose of setting up a proton gradient
b. it explains how the energy that helps to make ATP in the chloroplasts is generated
c. a and b
d. it explains how electrons are added to NADPre
e. it explains why Ralph Nader is such a jerk. (Come to think of it - nothing explains that)
37. The importance of the Krebs (citric acid) Cycle in cell metabolism is that it ______.
a. makes important biochemical intermediates c. makes NADox e. a, b and d
b. makes FADre d. makes ATP
38. Fermentation permits continuous glycolysis in plants because ______.
a. it serves to recycle NADre, which is needed for glycolysis d. lactic acid is produced, recycling NADox
b. it serves to recycle NADox, which is needed for glycolysis e. b and d
c. there is a net increase in the production of NADPox
39. Which statement below about noncyclic photophosphorylation is true?
a. ATP is produced from the electron derived from the Photosystem II reaction center.
b. O2 is produced when H2O is split
c. a and b
d. The electron from the Photosystem I reaction center ends up back in Photosystem I.
e. Electrons from Photosystem I drive the production of ATP.
40. A scientist isolates two specific mRNAs. One codes for the enzyme tigerase, a really good golfer enzyme that strays; the other codes for the enzyme beckase, a blowhard enzyme that fake cries on TV and knows a lot less than it thinks. Both mRNAs are placed in a test tube with RER vesicles stripped of their ribosomes, free ribosomes and precursors for protein synthesis. When the protein synthesis reaction is complete, beckase is found in the liquid portion of the test tube outside the vesicles; tigerase is found inside the vesicles. What can one conclude about the two proteins?
a. Beckase is a secretory protein; tigerase is a domestic protein.
b. Beckase is a domestic protein; tigerase is a secretory protein.
c. Both proteins are secretory.
d. Both proteins are meant for domestic use.
e. Tigerase diffuses into the vesicle after synthesis; beckase is an intrinsic membrane protein.
41. Which of the following sequences is most likely to be part of a signal peptide of a secretory protein.
Refer to the diagram of amino acid R groups on the last page of the multiple choice section for help.
a. — gly - asp - met - glu - asp - gly - lys - arg - met —
b. — cys - arg - glu - lys - lys - arg - gly - met - asp —
c. — arg - leu - asp - lys - phe - glu - arg - pro - leu —
d. — lys - ala - met - gly - phe - gly - leu - pro - met