In an experiment the transport of the neurotransmitter serotonin into cultured mammalian cells was measured. Batches of cells were incubated with solutions of different concentrations of radio labelled [3H]-serotonin for

a defined time, cells were then separated from the incubation buffer, and serotonin accumulated into the cells was determined by scintillation counting. The rate of transport is given as dpm/min* (see table below). In order to elucidate the transport mechanism, the experiment was conducted under two different conditions, i.e., in condition A normal transport buffer was used, and in condition B the transport buffer did not contain any Na* ions.[Notes: * dpm/min means disintegrations per minute and is a measure of the intensity of-radioactivity of a radio-labelled compound; it is directly related to the rate of transport for this compound] 11. Draw a graph (by using Excel or similar), plotting the serotonin concentration against the-transport rate under both conditions. (5 Marks). 12. What transport rates for each condition would you expect if the experiment was repeated-using 12μM [³H] serotonin? Add your estimate into the table above. (5 Marks). 13. Examine the plot obtained for condition A; what can you conclude with regards to-whether or not the transport of serotonin into these cells requires a protein? Explain your conclusion. (10 Marks). 14. Compare the plots of the transport rates for both conditions. What is most likely mechanism of transport for serotonin into these cells? Explain your interpretation. (10Marks).