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CBLG midterm 1

YOUR NAME:_________________________________________________________
YOUR STUDENT NUMBER: ____________________________________________
May 19th, 2015
INSTRUCTOR: Drs. Costin Antonescu and Roberto Botelho
You have 75 MINUTES to complete this examination
This examination is comprised of 35 multiple-choice questions each worth 2 points. Total 70 marks.
There are 8 pages (including this one) in this examination.
At the end of the examination, you must return:
1) This question sheet including all its pages
2) Your completed bubble sheet with your answers.
Make sure to follow the instructions given for completing the scanning sheet.
Good luck!
Answer EACH of the following questions by filling in the corresponding answer on the bubble
sheet. There is only ONE correct answer per question. Each question is worth 2 marks. Any answers
indicated on this question sheet will not be graded; only the bubble sheet will be graded for this section.
You will not be given additional time to copy your answers from this sheet to the bubble sheet.
1. Which of the following about specific macromolecules is FALSE?
(A) Proteins are formed by condensation reactions between amino acids.
(B) RNA (ribonucleic acid) is formed by condensation reaction between nucleotides.
(C) Proteins are formed by condensation reactions between monosaccharides.
(D) Starch is formed by condensation reactions between specific simple sugars.
(E) none of the above.
2. Protein secondary structure
(A) refers to the order of specific amino acids within a protein polymer.
(B) refers to the length of a protein (the total number of amino acids).
(C) can be made up of α-helix or β-sheets.
(D) does not contribute to protein function.
(E) is one aspect of proteins structure that is not found in integral membrane proteins.
3. Which of the following best describes the possible functions of integral membrane proteins?
(A) adhesion molecules
(B) transporters
(C) channels
(D) receptors for hormones
(E) all of the above
4. Green fluorescent protein (GFP)
(A) is a protein that is derived from jellyfish.
(B) is useful as a way to label proteins for electron microscopy.
(C) cannot be used to visualize the localization of proteins.
(D) is a special kind of lipid.
(E) none of the above are true.
5. Which of the following is the best explanation of how deconvolution microscopy allows removal
of out-of-focus light?
(A) it has an objective with a low numerical aperture, which decreases the light captured.
(B) it involves computer software that analyzes and de-blurs images after they are taken.
(C) it involves the use of a pinhole that limits the detection of out-of-focus but not in-focus light.
(D) it has a unique dichroic mirror that filters out light of specific wavelengths.
(E) all of the above.
6. Which of the following phospholipids is found predominantly on the inner leaflet of the plasma
membrane (with the headgroup facing the cell interior?
(A) phosphatidylserine
(B) phosphatidylcholine
(C) sphingomyelin
(D) phosphatidyluracil
(E) none of the above
7. The cellular structure that controls the organization of the microtubule cytoskeleton is
(A) the peroxisome, a membrane-bound organelle
(B) the centriole, a non-membrane-bound organelle
(C) the lysosome, a non-membrane-bound organelle
(D) the Golgi apparatus, a membrane-bound organelle
(E) the nucleolus, a membrane-bound organelle
8. Which statement if FALSE about membranes:
(A) Lipids are uniformly distributed in membrane bilayers.
(B) Membrane bilayers of different organelles can have different compositions.
(C) Membrane bilayers are made of cylindrical-shaped phospholipids.
(D) The two membrane leaflets of a bilayer can be different in composition.
(E) Phospholipids can be made to spontaneously form structures called liposomes in a test tube.
9. Bacteriorhodopsin
(A) is a protein with seven transmembrane domains.
(B) has a molecule called retinal within it that absorbs light.
(C) transports protons (H+) across the membrane.
(D) can be organized into larger structures on the cell surface.
(E) all of the above.
10. Protein phosphatases
(A) cause a particular GTPase protein to bind GTP, which makes the GTPase active.
(B) cause a particular GTPase protein to bind GDP, which makes the GTPase active.
(C) cause a protein to be phosphorylated, which is the colavent attachment of a phosphate group.
(D) cause the removal of a covalently attached phosphate group from a protein.
(E) causes the activation of protein substrates in all cases.
11. Which of the following about antibodies is FALSE?
(A) Antibodies are made by B-cells; there are billions of B-cells in every human (or mouse), and
each type of B-cell makes only one type of antibody.
(B) Each type of primary antibody binds every single type of protein, but the secondary antibody
only binds to some primary antibodies, allow specific labeling in a sample.
(C) Each primary antibody binds only to one type of protein, but the secondary antibody binds to
many types of primary antibody, allowing specific labeling in a sample.
(D) Antibodies can be linked to either fluorescent molecules for use in immunofluorescence
microscopy or with gold nanoparticles for use in immunoelectron microscopy.
(E) Antibodies are not needed to study the cellular location of integral membrane proteins since
all of these are fluorescent already (with no other modifications).
12. Which of the following are found in eukaryotic cells but not prokaryotic cells?
(A) DNA as the chemical store of genetic information
(B) lipids
(C) a plasma membrane
(E) mitochondria
(E) all of the above
13. Which of the following is the best explanation for how the nucleus may have arisen during the
early evolution of eukaryotic cells from a last universal common ancestor (LUCA)?
(A) The nucleus arose as a result of phagocytosis of other cells in predatory cells.
(B) The chloroplast arose before the nucleus.
(C) The nucleus is continuous with the Golgi apparatus and evolved after the Golgi apparatus.
(D) The nucleus was likely present in the last universal common ancestor.
(E) The nucleus arose by ingression of the plasma membrane, eventually surrounding the DNA.
14. Transbilayer diffusion
(A) refers to lipids moving laterally in the plane of the lipid bilayer.
(B) is very efficient and occurs at a high rate in most lipid bilayers.
(C) is required for the formation of lipid rafts.
(D) is responsible for the formation of integral membrane proteins.
(E) none of the above.
15. Which of the following would be useful to resolve features in a biological sample that are
smaller than 200 nm?
(A) the naked eye
(B) differential-contrast interference microscopy
(C) confocal microscopy
(D) deconvolution microscopy
(E) transmission electron microscopy
16. A phosphoanhydride bond is
(A) found between simple sugar groups in a large carbohydrate polymer.
(B) found between some proteins and their lipid anchors.
(C) found in lipids between fatty acids and glycerol.
(D) found in proteins between each individual amino acid component.
(E) found in adenosine triphosphate (ATP).
17. Which of the following allows the study of protein movement or dynamics?
(A) electron tomography
(B) indirect immunofluorescence microscopy
(C) immunogold transmission electron microscopy
(D) deep etching and metal shadowing
(E) none of the above
18. Which of the following best describes photoactivatable (PA) green fluorescent protein (GFP)?
(A) GFP is first subjected to photobleaching, which then allows GFP to later be activated by
reversing the photobleaching, which is called PA-GFP.
(B) PA-GFP is a derivative of regular GFP made by some specific changes to a few amino acid
groups in GFP such that it is not fluorescent prior to bright illumination with near-UV light.
(C) PA-GFP can only be used in fixed and embedded samples, and cannot be used to study the
movement of molecules within a cell.
(D) PA-GFP is a derivative of regular GFP made by some specific changes to a few amino acid
groups in GFP such that it emits red and violet light instead of green fluorescent light.
(E) none of the above
19.Which of the following electron microscopy techniques allows direct observation of organic
samples (no labeling)?
(A) Electron tomography
(B) Deep-etching and metal shadowing
(C) Immunogold electron microscopy
(D) Negative stain electron microscopy
(E) Cryo-electron microscopy
20. Which of the following combinations of microscope properties and fluorescent molecule
properties provide the best resolution? (NA refers to the numerical aperture of the objective lens)
(A) NA = 1.41; excitation wavelength = 460 nm; emission wavelength = 511 nm
(B) NA = 1.29; excitation wavelength = 534 nm; emission wavelength = 584 nm
(C) NA = 1.02; excitation wavelength = 370 nm; emission wavelength = 418 nm
(D) NA = 1.39; excitation wavelength = 370 nm; emission wavelength = 405 nm
(E) NA = 1.25; excitation wavelength = 633 nm; emission wavelength = 705 nm
21. A dichroic (or beam-splitting) mirror is
(A) has properties that allow it to differently impact light of different wavelengths.
(B) is a critical component of the scan-head scanning electron microscope.
(C) needed to detect light after it passes through the pinhole in a confocal microscope.
(D) is used to polarize light for use in a differential contrast interference microscope.
(E) often tells the Evil Queen in Snow White that she is the fairest in all the land.
22. Which of the following is not a feature of lipid rafts:
(A) they are enriched in cholesterol
(B) they are thicker lipid bilayer relative to other non-lipid raft regions of the membrane
(C) they have more ordered packing of lipids than non-lipid raft regions of the membrane
(D) they are enriched in phospholipids with unsaturated fatty acids
(E) none of the above
23. Which of the following about peripheral membrane proteins are TRUE?
(A) Peripheral proteins must have a consecutive stretch 20-30 amino acids that are hydrophobic.
(B) Peripheral proteins cannot be removed from binding membranes by adding high salt.
(C) Peripheral proteins readily allow communication across a lipid bilayer.
(D) Peripheral proteins are proteins that completely traverse the lipid bilayer.
(E) none of the above
24. Akt is regulated by
(A) binding to GTP, such that this protein is active when bound to GTP.
(B) binding to GDP, such that this protein is inactive when bound to GTP.
(C) phosphorylation by kinases, such that this protein is active when phosphorylated.
(D) phosphorylation by phosphatases, such that this protein is inactive when phosphorylated.
(E) electron microscopy.
25. When considering only a reaction that forms a large macromolecule from smaller molecules
(and not any other “coupled” reactions),
(A) this is always favorable since it involves an increase in enthalpy and decrease in entropy.
(B) this is always favorable since it involves a decrease in enthalpy and a decrease in entropy.
(C) this is always unfavourable since it involves an increase in entropy and an increase in
(D) this is often unfavourable since this involves a decrease in entropy and may also have an
increase in enthalpy.
(E) none of the above
26. A hydropathy plot measures
(A) the relative hydrophobic properties of amino acids along the length of a protein.
(B) whether a protein will have α-helix or β-sheets.
(C) whether the bonds in a protein polymer are endergonic or exergonic.
(D) the types of bonds between simple sugars in a polysaccharide.
(E) none of the above.
27. Fluorescence is a phenomenon that involves
(A) absorbance of light of a particular wavelength and formation of a new covalent bond.
(B) absorbance of light of a particular wavelength and nearly instantaneous emission of light of a
lower (shorter) wavelength.
(C) absorbance of light of a specific wavelength and nearly instantaneous emission of light of a
higher (longer) wavelength.
(D) conversion of energy released by a chemical reaction into light emission.
(E) absorbance of light of a particular wavelength followed by near instantaneous emission of
directed electrons.
28. Which of the following is the membrane-bound organelle that is responsible for breakdown
(degradation or digestion) of particular cellular components?
(A) the nucleus
(B) the chloroplast
(C) the peroxisome
(D) the plasma membrane
(E) the lysosome
29. Embedding is a term used to describe
(A) labeling of a sample with a dye to better visualize certain types of molecules.
(B) the permeation of a wax through a sample to harden it, allowing further processing.
(C) taking an optical section of a sample, such as in confocal microscopy.
(D) attaching fluorescent molecules to antibodies for use in electron microscopy.
(E) taking a nap just before doing microscopy.
30. The resolution limit of light microscopy is the result of
(A) inefficient lenses, which can be improved by a better and more expensive light microscope.
(B) diffraction of light as light passes objects similar proportional in size to the wavelength.
(C) the fact that some fluorescent molecules are damaged by photobleaching.
(D) the distance between the objective and ocular lens in a compound microscope.
(E) microscopes eating a diet high in gluten and bisphenol A (BPA).
31. In the diagram shown below, the portion of the phospholipid shown below corresponds to a
molecule named
(A) choline
(B) glycerol
(C) sphingosine
(D) ethanolamine
(E) ceramide
32. Which of the following about experimental methods to introduce probes or DNA into cells is
(A) Microinjection is useful to introduce DNA into millions of cells at the same time.
(B) Ballistic transformation uses electrical stimulation to temporarily perforate the cell.
(C) Electroporation can only introduce probes into a small number of cells at a time.
(D) Fusion of vesicle carriers with the plasma membrane can introduce DNA into many cells.
(E) none of the above.
33. Which of the following are forms of fluorescence microscopy?
(A) brightfield microscopy
(B) staining of neurons with silver nitrate
(C) phase contrast microscopy
(D) dark field microscopy
(E) none of the above.
34. Fluorescein is
(A) a dye that increase in fluorescence when bound to Ca2+.
(B) a dye that increases in fluorescence when bound to lipid membranes.
(C) a dye that changes fluorescence intensity with changes in pH.
(D) a dye that binds to the cytoskeleton (to actin filaments).
(E) a dye that binds to deoxyribonucleic acid (DNA).
35. Which of the following is NOT the spontaneous behavior of phospholipids when found in an
aqueous solution?
(A) the formation of a flat membrane sheets from an enclosed membrane.
(B) the formation of an enclosed membrane from a flat membrane sheet.
(C) the formation of a lipid bilayer.
(D) the packing of specific lipids together away from other types of phospholipids.
(E) van der Waals interaction forming between the hydrocarbon chains of some phospholipids.