The fragments of huntingtin protein also form aggregates with a nuclear transport protein known as Ran-GAP. How does Ran-GAP aggregating with huntingtin protein fragments disrupt nuclear protein transport?

According to the “Hawaiian Punch” principle, different compartments of the secretory and endocytic pathways are topologically equivalent to each other and to the extracellular space. Explain how vesicular transport generates this topological equivalence. These compartments are topologically equivalent because molecules can move between them without having to move out of the cell. Transport vesicles cause this “topological equivalence” because they are responsible for the actual movement of the molecules mentioned above. They break off from one compartment, carrying the necessary molecules, and then fuse to its targeted compartment; thus, making the compartments topologically equivalent.  During mitosis in mammalian cells, the nuclear envelope breaks down into vesicles. Are the topological properties of the cell altered by this event? Justify your answer.

If cells are treated with colchicine, a drug that promotes microtubule disassembly, the location of the ER and Golgi both change dramatically.  Rather than being spread out quite widely through the cytoplasm, the ER appears to collapse into the area near the nucleus. (Recall that the ER membrane and the outer nuclear envelope are continuous with one another). In contrast, the Golgi stacks disperse from their usually more compact, central location to areas all over the cell. However, if colchicine is removed, and microtubules are allowed to reassemble, both organelles eventually return to their normal distribution in the cells. How do you account for the change in distribution of the ER & Golgi when microtubules are depolymerized? What protein(s), other than tubulins, allow normal cellular organization to be restored once colchicine is removed? (answer should include information to explain both the ER & Golgi)

The following image is based on real results from an influential experiment in cell biology.  This experiment studied the role of the proteins Ran and importin in nuclear protein transport.  The experiment used flourescently-labeled proteins containing a nuclear localization sequence (the "substrate").  Ran, importin, and GTP were either present or absent, as indicated in the figure.  Cells were exposed to these different conditions and then analyzed by fluorescence microscopy. Circles are the cells' nuclei.  Very light circles are the nuclei without the substrate attached. Study the figure below and then answer the questions that follow. 1. What actions does Ran perform by itself? 2. What actions does importin perform by itself? 3. How do Ran and importin act together in the nuclear import of protein? 4. Why is GTP required?

Is the movement of sodium through SGlut-1 during co-transport simple diffusion, facilitated diffusion, active transport, or secondary active transport? And is the movement of glucose through SGlut-1 during co-transport simple diffusion, facilitated diffusion, primary active transport, or secondary active transport?

List and describe the three main types of cytoskeleton. If you wanted to do immunocytochemistry to specifically stain each type of cytoskeleton, what is a protein that could be used for each cytoskeletal type (in other words, what is a unique protein for each cytoskeletal type)? What are three types of actin structures? Describe the involvement of actin structures in cell migration. How is the growth and shrinking of microtubules regulated? Then describe the roles of microtubules in: chromosomal separation during mitosis and the movement of organelles and vesicles within a cell. Describe a possible mechanism on how signaling pathways might impact the cytoskeleton, so that cell migration could be regulated in a localized manner within a multicellular organism. (hint: think about the possible transcriptional regulation of the G-protein regulators) What are 2 main challenges of protein targeting? Then describe one way these challenges are overcome during signal-based targeting and one way…

What is an analogy for a smooth endoplasmic reticulum?

IN the figure for D: The organization of a protein that normally resides in the plasma membrane in shown in the figure below. The boxes labeled 1,2 3 and 4 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true? (C) (D) oplasmic Reticulum The N-terminus of this protein is in the ER lumen The mature version of this protein will span the membrane twice, with both the N- and C-terminus in the cytoplasm. Two of the answers are correct The C-terminus of this protein is in the ER lumen

Diagram the functional role of the phenylalanine-glycine repeats (FG repeats) in facilitating the passage of nuclear import/export receptor passage through the nuclear pore complex. Do the FG repeats function to change the DGrxn (thermodynamics) or the DG‡ (activation energy)?(2 pts.)

Consider the amino acids on the image below. Which of the following amino acids would be most likely to be found in the part of an integral membrane protein that is located within the membrane? (Select all answers that apply.) Asparagine (Asn)   Lysine (Lys)   Phenylalanine (Phe)   Valine (Val)   Glutamic acid (Glu)  Methionine (Met)