Question

29 Figure Q12-4 shows a recording from a patch-clamp expeniment in which the electrical current passing across a patch of membrane is measured as a function of time The membrane patch was plucked from the plasma membrane of a muscle cell by the technique shown in figure 12-24 in the textbook and contains molecules of the acetylcholine receptor, which is a ligand-gated cation channel that is opened by the binding of acetylcholine to the extracellular face of the channel To oblain a recording acetyicholine was added to the solution inside the microelectrode a) Describe what you can learn about the channels from this recording b) How would the recording difer if acetylcholine were () omited or (il) added to the solution outside the microelectrode only? 2 pA 10 msec Paragraph ▼ |B 1 |ΕΞΙίΞ A) from, this channel you visualize the action potential generated by applying a stimulus

Answer 1

(A) From the figure, it can easily be understood that upon opening of ligand gated cation channel, selective ions moves across it and manifest either a positive or negative current.As can be noticed in the figure, a positive current is flowing through the cation channel.

(B)In both the cases when acetylcholine is omitted or added in the solution outside the microelectrode, the current readings will be absent.It is because, In patch clamp technique the ligand gated cation channel spanning the microelectrode tip only will give the current readings upon acetylcholine binding.