Please, Give a Plausible Explanation on Why Gated Transport Can Only Transport Properly

Biology 121 – Molecular Cell Biology Fall 2011 - Exam 1 Version 2

Name: ______

1. The lipid bilayer is considered to be amphipathic because ______. a. It contains both hydrophobic and hydrophilic regions b. It contains both positive and negative charges c. It contains both lipids and protein components d. There are two different layers (or leaflets) e. It contains both phospholipid and cholesterol

2. Which of the following is not a type of membrane protein? a. Transmembrane glycoprotein b. Sphingomyelin c. P-type pump d. Channel protein e. None of the above

3. Which of the following is not a function of membrane proteins? a. Transport ion of polar molecules b. Activation of signal transduction pathways c. Cell-cell recognition d. Enzymatic activity e. ATP-dependent intracellular transport

4. Which of the following structures and activities does not involve actin filaments? a. Cell migration through diapedesis b. Formation of focal adhesions c. Movement of mucus carrying debris through the airway d. Muscle contraction e. Mitotic contractile ring

5. What is the function of a Microtubule Organizing Center (MTOC)? a. Bound by ARP for the nucleation of actin filament b. Bound by ARP for the nucleation of microtubule c. Bound by -Tubulin ring complex (-TuRC) for the nucleation of actin filament d. Bound by -Tubulin ring complex (-TuRC) for the nucleation of microtubule e. Regulates the nucleation of intermediate filament

6. Which of the following is required for a vesicle destined for the lysosome? a. Both myosin binding capacity and kinesin binding capacity b. Both Golgi rab proteins and lysosomal rab proteins c. A mannose-6-phosphate receptor protein d. An inactive hydrogen ion pump e. All of the above

7. What order do events occur in chemotactic migration? a. g-actin addition to f-actin, ATP exchange in actin, rho activation, removal of g-actin by cofilin b. ATP exchange in actin, rho activation, removal of g-actin by cofilin, g-actin addition to f-actin c. rho activation, removal of g-actin by cofilin, ATP exchange in actin, f-actin addition to g-actin d. rho activation, ATP exchange in actin, g-actin addition to f-actin, removal of g-actin by cofilin e. None of the above Use the following figure to answer questions 8 and 9.

8. This figure represents ______. a. A hemidesmosome b. Desmosome c. An occluding junction d. A focal adhesion e. An intercalated disc

9. Which of the following statements about adhesion proteins is true? a. A functional integrin protein is dimer of two peptides. b. Adhesion proteins bind to cytoskeleton proteins. c. Internal binding and external binding are unrelated. d. Integrin must be linked to either microtubules or nuclear lamin. e. All of the above are true.

10. Which of the following molecules is not amphipathic? a. Cholesterol b. Glucose c. Phosphotidyl serine d. Adrenaline receptor e. Galactocerebroside

11. Which of the following is not true about membranes? a. They are as fluid as salad oil b. Saturated fatty acids make them less fluid c. At warm temperatures cholesterol makes them less fluid d. If there are enough amphipathic molecules they will spontaneously form in water e. None of the above

12. Which of the following combinations of molecules are able to diffuse through our membranes? a. Oxygen, carbon dioxide, water, urea b. Calcium, carbon dioxide, water, peptides c. Oxygen, amino acids, water, estradiol d. None of the above e. All of the above

13. Why is the lipid:protein ratio of the oligodendrocyte or Schwann cell plasmamembrane 80:20? a. Its function is to group enzyme cascades for energy production b. Its function is to selectively facilitate the diffusion of steroid hormones into the cell c. Its function is to selectively facilitate the diffusion of water out of the cell d. Its function is to selectively block sodium and potassium ions from crossing e. Its function is to selectively block calcium ions from crossing 14. Which of the following is not a function of the membranes in cells? a. Compartmentilization of cell functions b. Selective permeability in two directions c. Organization of the chromosomal DNA in the nucleus d. Attachment and movement of the cell or compartment e. Response to signals from outside of the cell or compartment

15. Which of the following is not a function of the endoplasmic reticulum? a. Calcium sequestration b. Detoxification of dangerous materials c. Lipid biosynthesis and protein translation d. Targeting of vesicles for final destinations e. Integration of membrane lipid and protein

16. What is meant by the cytosolic-to-non-cytosolic relationship in the endomembrane system? a. Material only flows from the inside of a cell to the outside b. The fluid inside of a cell interacts with the solids that are dispersed within it c. There is a separation between the contents of the nucleus and those of the cytosol d. The proteins and lipids that face one side of a membrane can never face the other side e. None of the above

Use the following figure to answer questions 17-19.

17. Which of the following processes is not represented in this figure? a. Cells using flagella to swim through blood b. Cell rolling (or rolling adhesion) c. Cell-to-cell adhesion d. Diapedesis e. None of the above

18. What molecular mechanism(s) is required for extravasation of white blood cells (WBC) from the blood vessel? a. Endothelial integrin binding to ICAM family adhesion proteins on the WBC b. Endothelial selectin binding to short sugar chains on the WBC c. Chemotactic stimulation of actin-myosin migration d. Both a and b e. Both b and c

19. What keeps WBC from adhering and leaving the blood vessel all of the time? a. Contraction of the smooth muscle of the blood vessel b. The blood pressure that results from contraction of the heart muscle c. The lack of active adhesion molecules on normal endothelial cells d. Both a and b e. Both b and c This figure represents the endomembrane system. Use it to answer questions 20-22.

20. Which component or components of the endomembrane system is not shown in this figure? a. Transport vesicles b. Nucleus c. Golgi apparatus d. Endosomes e. Lysosome

21. What proteins control specific organelle targeting in the endomembrane system? a. Dynamin b. Rabs and Snares c. Clathrins d. Kinesin binding proteins

22. Which of the following proteins are transported through the endomembrane system? a. Subunits for the cytoskeletal fibers b. Motor proteins c. Glycolysis enzymes d. Glycosylating enzymes e. None of the above

23. Which of the following is a function of the chloroplast? a. Reactive oxygen species metabolism b. Store, protect, express their own DNA c. Phagocytosis d. Endocytosis e. Control of water and ion exchange

24. What forces play a significant role in determination of the final configuration of a protein? a. Covalent bonds b. Electrostatic bonds c. Vander Waals forces d. Hydrogen bonds e. All of the above

25. What mechanisms play a significant role in the cell’s control of protein activity? a. Cleavage of a portion of the peptide b. Negative allosteric regulation c. The addition of a covalent subgroup d. All of the above e. None of the above

26. Which of the following is not a covalent linkage? a. Glycosylation b. Phosphorylation c. Actin subunit assembly d. None of the above e. All of the above 27. Which of the following is not a required element of Src kinase activation? a. Dephosphorylation b. Phosphorylation c. Ligand binding d. Conformation change in Src structure e. None of the above

28. Which of the following is not a mechanism by which cells can control protein activity? a. Regulation of the presence of a signaling molecule b. Regulation of the presence of a substrate molecule c. Regulation of a molecule that blocks its binding site d. Regulation of its assembly into a polymer e. Regulation of its secondary structure

29. Diffusion of ions across a cell membrane is driven by ______. a. An electrical force only b. A chemical force only c. A electrical force only if the chemical force isn’t present d. A combined electrical and chemical force e. An active transport protein

30. What mechanism allows a cell to attach and detach during migration? a. The binding of actin to the transmembrane adhesion proteins causes it to release external binding b. The pulling of myosin on actin causes transmembrane adhesion proteins to release external binding c. Internal binding of transmembrane adhesion proteins is required for external binding to occur d. External binding of transmembrane adhesion proteins is required for internal binding to occur

Use the following figure to answer questions 31 and 32.

31. Which of the following statements is true about actin filament polymerization? a. Thymosin-bound G-actin subunits are used for actin filament polymerization. b. Profilin-bound G-actin subunits are used for actin filament polymerization. c. Cofilin-bound G-actin subunits are used for actin filament polymerization. d. Profilin binds to the plus end of actin filament to promote polymerization. e. Thymosin binds to the plus end of actin filament to promote polymerization.

32. What are absolutely required for the nucleation of actin filament? a. ARP and/or formin, profilin, and G-actin, b. ARP and/or formin, thymosin, and G-actin c. Formin, thymosin, and F-actin d. Profilin, thymosin, and cofilin e. ARP and/or formin, G-actin

This figure represents the various types of membrane proteins. Use this figure to answer questions 33 and 34.

33. Which of these proteins may possibly act as an adhesion protein (like integrin or cadherin)? a. protein 1 b. protein 3 c. protein 5 d. protein 6 e. protein 7

34. Which of the following proteins can possibly link an adhesion protein to its respective cytoskeleton (like intermediate filament or actin filament)? a. protein 1 b. protein 3 c. protein 5 d. protein 6 e. protein 7

35. What order of ion release through their channel proteins is essential for neural release of neurotransmitter? a. Sodium, potassium, calcium b. Sodium, calcium, potassium c. Calcium, sodium, potassium d. Calcium, potassium, sodium

36. What cytoskeletal process is needed to move vesicles from the cell body to the synapse? a. Myosin transport along intermediate filaments b. Myosin transport along microfilaments c. Kinesin transport along microtubules d. Kinesin transport along microfilaments e. Dynein transport along microtubules

37. What happens to the vesicles with neurotransmitter when they arrive at the synapse? a. They immediately fuse with the plasmamembrane and release neurotransmitter b. They immediately fuse with the plasmamembrane and release enzymes to make neurotransmitter c. They stay on the cytosolic side of the membrane and release neurotransmitter d. They stay on the cytosolic side of the membrane until signaled to fuse e. They pass through membrane channels and bind to the post-synaptic cell membrane

38. How do the important protein receptors and channels in the synapse remain where they need to be relative to each other? a. They are bound to the cytoskeleton inside the cell b. Scaffolding proteins hold the complex together c. They are bound to the extracellular matrix outside of the cell d. The lipids keep them from moving away from the site that they were placed in originally e. None of the above

39. Why are sugar molecules found on the extracellular face of the plasma membrane? a. Glycosylating enzymes are only on the extracellular face of the plasma membrane b. Glycosylating enzymes are only on the surface of golgi apparatus and endoplasmic reticulum c. Glycosylating enzymes are only in the lumen of golgi apparatus and endoplasmic reticulum d. Both a and c 40. Which of the following is not true of the submembrane protein meshwork? a. Always on the noncytosolic face b. Allows membrane to communicate with the rest of the cell c. Segregate and establish functional domains in the membrane d. Contain ribosome docking proteins e. Contain chaperonin docking proteins

41. Which of the following statements is true about vesicular transport? a. Vesicles bud off of a membrane due to kinesin binding capacity in the membrane meshwork. b. Vesicles are transported along actin filaments to their next membrane due to coat proteins. c. Dynamin finishes the vesicle budding process started by COP II proteins d. Vesicles fuse to their destination membrane due to their total protein constituents. e. All of the above

42. Which of the following is true about the membrane of different organelles? a. Each membrane possesses its own lipid signature. b. All plasma membranes possess a similar carbohydrate signature. c. With respect to the two faces (or leaflets) of each cell membrane, the lipid signature is symmetric. d. With respect to the two faces (or leaflets) of each cell membrane, the protein signature is symmetric. e. All of the above

43. Which of the following is true about the involvement of cell membranes in vesicular transport? a. Only membranes that have similar lipid signatures can fuse together. b. The protein signature helps guide the vesicle to its target membrane. c. Lipid and protein signatures are required for delivery of a vesicle to its proper target organelle. d. All of the above e. None of the above

Use the following figure above to answer questions 44 and 45.

44. Which of the following statements describes the mechanism for cytokinesis? a. Only the contractile activity of actin and myosin filaments is required in cytokinesis. b. Assembly of the contractile ring followed by contraction, then gelsolin activity is required in cytokinesis. c. Assembly of the contractile ring followed by rapid profilin activity is required in cytokinesis. d. Assembly of actin filaments followed by rapid disassembly of microtubules is required in cytokinesis. e. The preformed contractile ring undergoing further assembly is required in cytokinesis.

45. Which of the following is not involved in the assembly of the contractile ring? a. G-actin b. Myosin c. ARP and/or formin d. Profilin e. Katanin

Use the following figure above to answer questions 46-47.

46. This ring of doublets surrounding a pair of singlets (9+2) struture represents ______. a. The tubulin protein structure found in the cilium of a human epithelial cell b. The tubulin protein structure found in the flagellum of prokaryotes c. The flagellin protein structure found in the flagellum of unicellular eukaryotes d. The flagellin protein structure found in the tail of human sperm e. All of the above

47. This structure performs the above function by ______. a. The movement of kinesin molecules away from MTOC b. The movement of kinesin molecules toward MTOC c. The movement of dynein molecules away from MTOC d. The movement of dynein molecules toward MTOC e. None of the above

48. Which of the following are required for microtubule nucleation? a. -tubulin ring complex, tubulin, profilin b. -tubulin ring complex, tubulin, MTOC c. -tubulin ring complex, tubulin, MTOC, stathmin d. MTOC, tubulin, MAP2 e. Cilia, flagella, cell division

49. Which of the following statements is not true about microtubule disassembly? a. Severing catalyzed by katanin contributes to microtubule disassembly. b. Severing catalyzed by kinesin 13 contributes to microtubule disassembly. c. The binding of Tau at the plus end of the microtubule can prevent microtubule disassembly. d. Unphosphorylated stathmin molecules do not directly cause microtubule disassembly. e. Phosphorylated stathmins molecules do not directly cause microtubule disassembly.

50. Which of the following is required for rate limiting enzymes destined for the mitochondrion? a. Both myosin binding capacity and kinesin binding capacity b. Outer membrane lipid signature c. A mannose-6-phosphate receptor protein d. A free ribosome e. All of the above