1) When considering the mass transfer associated with a tissue-engineered device, why is it usually sufficient to only consider the flux of oxygen and not worry about the flux of glucose or other biological molecules? 2) Estimate the average distance between protein molecules on the surface of a cell. You should supply and justify any numbers or approximations you make. Compare your answer with the video we watched at the beginning of the semester The Life of a Cell". ( The video is about protein packing )

3) Electrodes implanted in the brain can be used to send and receive signals from the brain to a computer interface. Explain the molecular origin of the brains electrical signals. 4) Foreign materials that are implanted into the body generally cause an immune response. Describe several ways in which this response can be minimized or avoided