The transport of Potassium across a eukaryotic membrane canhappen by either a passive or an active transport. The activetransport is used when Potassium has to move against theconcentration gradient that is from a low concentration outsidecells to a high concentration inside cells. Ion channels mediatethe passive transport and these transport ions from a highconcentration to a low concentration.
The Potassium channel is very selective for the transport ofPotassium.
a) Explain how the selectivity of the potassium channel is ensuredand why the smaller ion lithium will not be transported through thepotassium channel.
The gene encoding the Potassium channel in eukaryotes istranscribed into a pre-mRNA.
b) List the three elements in a pre-mRNA in eukaryotes that is notfound in a prokaryotic mRNA?
c) RNA polymerase II is responsible for the transcription of thegene encoding the Potassium channel; the carboxyl-terminal domainof the RNA polymerase II has a special function, describe thefunction?
d) Give the post-translational modification, which is responsiblefor the regulation of the activity of the carboxyl-terminal domainof RNA polymerase II.
