Question

1. Describe the path of proteins and RNAs entering and exiting the nucleus.  What types of molecules are more likely to enter?  To exit?

2. Compare and contrast importins and exportins. What determines whether molecules will be imported/exported?

Answer 1

Proteins idestined to be secreted move through the secretory pathway in the following order rough ER----ER to Golgi transport vesicles -------Golgi cisternae------ secretory or transport vesicles ------- cell surface. Messenger RNA become bound to the protein that are loaded onto the RNA as transcription and splicing proceed these proteins contains nuclear export signals that are recognised by export receptors that guide RNA out of the nucleus nucleus for complexes Nuclear pore complexes allow the transport of molecules across the nuclear and love this transport includes RNA and ribosomal protein moving from nucleus to the cytoplasm and proteins such as DNA polymerase and lemons carbohydrates signalling molecules and lipids moving into the nucleus.

The importance exporting transport system provides the machinery involved in nucleocytoplasmic transport alteration of the levels of importance and exports may play a crucial role in development differentiation and transformation.

Some molecules can diffuse through the cell membrane without any assistance from the cell .other requires the help of transmembrane proteins to move into or out of the cell . Three primary factors that determine whether a molecule will diffuse across cell membrane that are concentration ,charge and size.