Cell signaling

  1. Some drugs are made of fairly large polar molecules which cannot easily enter cells. To correct this problem,
    drugs are now being delivered into cells by containing them inside liposomes, in which the drug is surrounded
    by a phospholipid bilayer. Given what you have learned about phospholipids, cell membranes and polar vs
    nonpolar molecules, explain how the drug packaged in liposome enters the cell. (Note: I’m not looking for an
    answer you looked up. I’m more concerned with your logic.)
  2. Mackerel are cold-water fish that thrive at 12 °C but can survive at 4 °C. Assuming membrane fluidity
    remains the same, how will the composition of a mackerel’s cell plasma membranes change in terms of length
    of fatty acids in the membrane, the degree of unsaturation of fatty acids, and overall cholesterol concentration
    when the water’s temperature drops from 12 °C to 4 °C
  3. For the following biological phenomena, identify the signal and the response. There is no need to do
    research on each topic, I am looking for you to read the phenomena and answer using the information given.
    Example: Follicle-stimulating hormone stimulates a cell to secrete growth factors.
    Signal: Follicle-stimulating hormone
    Response: growth factor secretion
    Insulin levels in the blood lead to glucose being imported into fat cells.
    A growth factor stimulates the synthesis of proteins needed for a cell to grow
    An undifferentiated cell becomes a glial cell after coming in contact with a neuron expressing the Delta protein.
  4. Your book divides cell signaling into 4 stages: Receptor activation, signal transduction, response, and
    termination (see Figure 9.3).
    Place each of the following events into the correct stage of cell signaling
    a. A G protein catalyzes the hydrolysis of GTP to GDP and Pi
    b. Receptor kinase dimerizes after binding insulin
    c. Inactivation of a receptor kinase by a protein phosphatase
    d. Changes in gene expression
    e. Adrenaline binds the extracellular domain of a G protein-coupled receptor
    f. Activation of protein kinase A (PKA)

Sample Solution