Bio 213 Comprehensive Study Questions with Correct Answers

What is the difference between necessary and sufficient? Necessary means that something must be present in order for something to occur, and sufficient means it will produce the event. To get an A in a course a necessary condition might be to turn in a paper (without it you would fail) Describe a nuclear pore They are "gates" through both membranes of the nucleus that allow movement of molecules in both directions How many different types of proteins make up a nuclear pore and how many total proteins make up the pore? approximately 30 different kinds make up over 450 total What kind of molecules are allowed through a nuclear pore? small molecules diffuse freely What is needed in order to get a large molecule through a nuclear pore? A nuclear localization signal and helper proteins Describe protein transport through nuclear pores (Ran GTP/GDP cycle) A cargo protein wants into a nucleus, so a nuclear transport receptor binds to it to allow it through Once through, Ran-GTP binds to transport receptor and releases cargo protein (GTP added to nuclear transport receptor to drop cargo) Empty receptor with attached GTP leaves nucleus to go back to cytosol, the GTP is hydrolyzed (making the Ran-GTP into Ran-GDP) and the Nuclear transport protein is ready for the next round What kinds of proteins are transferred from the cytosol to ER? Soluble and Transmembrane Proteins How does a protein receive a signal sequence? A signal recognition particle in the cytosol recognizes the sequence and attaches the signal to the translocation channel before it is displaced and recycled.