1. For this problem, you will use the excel spreadsheet provided in your textbook. It is called “Ch13_hemoglobin.xlsx” and a link can found in Integrating Question 4 of BME 13.1
2. 
   pen the Excel file CH13_hemoglobin.xlsx, which contains the data on oxygen saturation of hemoglobin from Figure 13.1 and a Hill equation model for the data. Change the values of k and n at the top of the sheet labeled “Hill equation” to find the best fit to the hemoglobin data, judging by the similarity of the two curves in the graph.

Once you have the spreadsheet open, alter the values of n and k until you find the best fit of the modeling data to the observed data. What values of n and k best model the observed data?

1. Explain as best you can what the significance of n and k are. In other words, physically, what do n and k represent in the model? How are they connected to the actual hemoglobin molecule and how it works?
2. Consider a lambda phage in which some specific alterations have been made to specific proteins. Predict, as specifically as you can, how the lysogenic/lytic switch would behave if the following changes were made:
   a. cI protein monomers no longer were able to bind to other cI monomers. In other words, cI protein cannot dimerize.
   b. Operator 2 is altered such that both cro and cI bind to this operator best.
   c. cro protein can no longer bind to operator 3, but it binds normally to the other operators.
   d. cI protein is altered such that when it is bound to operator 2 it no longer acts as a positive transcriptional regulator for PRM.
3. Here is an interesting observation about quorum sensing in squid: When V. fischeri cells are genetically modified such that they are no longer capable of producing light, the host squid cuts off the nutrient supply to these bacteria and purges them to the environment, in hopes of being able to gather different bacteria that can bioluminesce.
   1. Why would squid want to do this? Would this ability to purge bacteria be advantageous to the squid?
   2. How do you think the squid know whether or not symbiotic bacteria are able to produce light or not?