Midterm 1 Flashcards
Epithelial cells lining the intestine take glucose out of the gut and into the cell using ___, which is made possible by establishing potential energy through the ___.
- Na+ symporter
- an Na+/K+ ATPase
Western blot on SDS-PAGE: Where does protein A reside if it is present in the crude lysate and 600xg pellet?
Nucleus
Western blot on SDS-PAGE: Which protein is most likely to be in the cytoplasm?
Only present in the crude lysate and supernatants
Western blot on SDS-PAGE: Which protein is most likely to be a membrane protein?
- Crude lysate
- 15,000xg supernatant
- 100,000xg pellet
T/F: An antiporter would function as a symporter if its orientation in the membrane were reversed (that is, if a portion of the protein normally exposed to the cytosol faced the outside of the cell instead).
False
T/F: Although lipid molecules are free to diffuse in the plane of the bilayer, they cannot flip-flop across the bilayer unless enzyme flippase is present in the membrane
True
What event requires active transport to maintain acidic pH in the stomach lumen?
Import of H+ into the stomach lumen and export of K+ from the stomach lumen by K+/K+ ATPase
Which protein would you not expect to find in a typical eukaryotic cell?
Lipid-anchored membrane proteins
NUC1 is a large protein that contains 3500 AAs. NUC1 fused to GTP localizes to the nucleus. When the first 10 AAs of NUC1 are expressed as fusion w/ GFP in cells, it localizes to the nucleus. We therefore conclude that the first 10 AAs of NUC1 are ___ for nuclear localization.
Sufficient
T/F: Membranes that contain many single pass and multi-pass transmembrane proteins are not fluid.
FALSE
Western blot on SDS-PAGE (control, + trypsin): If the protein doesn’t change after trypsin treatment, what type of membrane protein is it?
Peripheral cytoplasmic protein
Western blot on SDS-PAGE (control, + trypsin): If the protein travels faster after trypsin treatment, what type of membrane protein is it?
Transmembrane protein w/ large domain exposed outside
Western blot on SDS-PAGE (control, + trypsin): If the protein disappears after trypsin treatment, what type of membrane protein is it?
Peripheral extracellular protein
You are working w/ two proteins CaM and SOUL in your PhD thesis project. You perform a FRAP experiment to determine the turnover rate of SOUL protein compared to CaM. You see that CaM recovers its fluorescence while SOUL does not. What is your best conclusion?
CaM is more dynamic than SOUL
What does the Na+-K+ pump do? How does it work?
Dephosphorylation of the pump transports K+ into the cytosol
What is this: A membrane protein has binding sites for solute B and for solute A. This membrane protein can switch between that two conformational states only if both binding sites are occupied or if both sites are empty.
Symporter
You add a PKKKRKV to the end of a protein that normally localizes in the cytoplasm. Where would you now predict the new protein to localize?
The nucleus
What characteristic distinguishes plant cells from animal cells?
Plant cells have cell wall; animal cells do not
If you fuse lysine rich sequence to the N-terminus of the green fluorescent protein, where would you expect to see this protein in the microscope?
Nucleus
According to Singer and Nicolson’s proposed model, membrane contains what?
Proteins are embedded in the lipid bilayer and both lipids and proteins can freely diffuse
The conventional fluorescence microscope images are not as good as confocal laser scanning fluorescence microscope (CLSM) because?
None of the above
The gene Rb normally inhibits cell division. When the growth factors are present, Rb is inactivated to allow the cell to divide. A mutant form of Rb is found in many cancer tumors. The mutant form of Rb is inactive in the absence of growth factors. Rb is a ___?
Tumor suppressor gene
The complexity of genomes in multi-cellular organisms increases due to an expanded number of genes involved in ___?
Receptors
Which of the following is not true of GFP?
- GFP can be viewed using a fluorescence microscope
- GFP can be viewed in live cells
- GFP does not disrupt the protein it is fused to
- GFP can be used to study dynamics of proteins in a membrane
- GFP was originally identified from a jellyfish
GFP does no disrupt the protein it is fused to
Antibodies (IgG) are powerful reagents b/c they bind to a specific antigen via the ___ and bind to ___ via the Fc region.
- Variable domain
- Protein A
Why is dry lens resolution not as good as oil-immersion lens
Numerical aperture of dry lens is less than oil-immersion lens
Using sequential differential centrifugation steps, you fractionate cellular organelles from a wild-type and mutant cell line. You then run the fractions on SDS-PAGE and use antibodies against he C-term of your protein is in. Normally you find your favorite protein in the total cell lysate, the 600xg supernatant and the 15,000xg pellet. In the mutant cell line your favorite protein is still in the total cell lysate and the 600xg supernatant, but is now instead in the 15,000xg supernatant and the 100,000xg supernatant. Where are the wild-type and mutant versions located?
The wild-type is in the lysosome and the mutant version is in the cytoplasm
You isolate a loss of function mutation in a bacterial gene that codes for a fatty acid saturase. You are now proposing to analyze membranes from this mutant strain of bacteria. What do you expect to find?
An increase in the number of carbon double bonds and an increase in membrane fluidity
Cholesterol in animal cells functions to ___?
Stiffen the membrane and decrease the melting point
The Langmuir trough was used to support what model?
The membrane contains bilayer of lipids
