Trace the pathway of a protein from translation to the plasma membrane
When answering these four questions, you may use both writing (text) and drawings. However, all
drawings should be clearly labeled, and your answers may NOT consist only of drawings.
1. Trace the pathway of a protein from translation to the plasma membrane. You may name this protein
anything you want, but it must be a transmembrane protein (either single-pass integral membrane protein
or multipass channel protein), with the N-terminus on the cytosolic side of the plasma membrane. The
protein must also have several protein modifications, including (but not limited to) N-linked
glycosylation, cysteine disulfide bonds, lipid modifications, and 3-D folding.
You do not need to describe the processes of transcription or translation. Assume that transcription has
already occurred, and translation has begun, with the mRNA attached to the ribosome. You do, however,
need to describe the process(es) by which the protein is modified and transported to the plasma
Any accessory molecules encountered by your protein along the way must be returned to their starting
point or conformation.
2. Choose one of the following signal transduction pathways and trace the pathway of cell signaling from
the cell surface receptor to its effects on transcription.
In your answer, be sure to describe the cell surface receptor and its ligand, the intracellular signaling
pathway, and the regulation of this pathway, or the processes by which the signal is terminated. Also
remember that the signaling pathway you describe must go to the nucleus and affect transcription.
3. Briefly describe one voltage-gated ion channel and two protein pumps found in the heart. In your
answer, you should explain how the voltage-gated ion channel responds to voltage changes and how it
controls which ions pass through the channel. For the protein pumps, be sure to describe the structure of
the protein pump and any conformational changes that it goes through. Additionally, you should briefly
explain the importance of each ion channel or pump for the normal functioning of the cardiac muscle.
4. Briefly describe the cell cycle, its checkpoints, and the general proteins required to move past each
checkpoint. For each cell cycle checkpoint, be sure to describe what the cell is “checking for” and how
this “check” occurs, along with the result if the checkpoint cannot be passed. Your answer should also
include a description of the structure of MPF, its regulation, and its general targets or functions. Be sure to
include any accessory molecules or proteins involved in regulation of MPF, while also describing the
process by which MPF is formed and activated.
In this answer, you should also choose two proteins involved in the cell cycle, which, if mutated, will
cause cancer. Describe these proteins and their normal functions, and then show how a mutation in these
proteins will result in cancer.