Briefly describe the cell cycle, its checkpoints, and the general proteins required to move past each checkpoint.

Description
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 membrane.
   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.
   Wnt
   Hedgehog
   Cytokines
   Insulin
   Epinephrine
   Serotonin
   Glucagon
   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.