mastering bio 7.4-7.5

Which molecules do not normally cross the nuclear membrane? Proteins Nucleotide triphosphates DNA mRNA

DNA

What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell? ER → lysosomes → vesicles that fuse with plasma membrane nucleus → ER → Golgi ER → Golgi → vesicles that fuse with plasma membrane ER → Golgi → nucleus Golgi → ER → lysosome

ER → Golgi → vesicles that fuse with plasma membrane

True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.

False

Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins. After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results? The cytoplasmic protein contains a nuclear localization signal. Nucleoplasmin does not have a nuclear localization signal. One of the fusion proteins entered the nucleus by passive transport. Only one of the two fusion proteins possesses a nuclear localization signal.

Only one of the two fusion proteins possesses a nuclear localization signal.

A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place? Active transport Osmosis Passive transport

Passive transport

Which of the following statements about the nuclear envelope is false? The nuclear envelope is composed of two lipid bilayers. The nuclear envelope is continuous with the Golgi apparatus. Molecules pass into and out of the nucleus through nuclear pores. Nuclear pores are made up of a group of proteins that are collectively called the nuclear pore complex.

The nuclear envelope is continuous with the Golgi apparatus.

Which statement most accurately describes what happens to proteins that lack an ER signal sequence? They are inserted into the plasma membrane. They are inserted into the ER membrane but do not enter the ER lumen. They are released into the cytosol. They bypass the ER but enter the Golgi apparatus.

They are released into the cytosol.

How are these signals read? They bind to receptor proteins. They are glycosylated by enzymes. They enter transport vesicles. They bind to motor proteins.

They bind to receptor proteins.

In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules? To make the proteins bigger To make the proteins easy to see To give the protein molecules energy To target the proteins to the nucleus

To make the proteins easy to see

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis? on the ER on the outer surface of the nucleus on the inside surface of the cell membrane on the inside surface of the vesicle on the outside of vesicles

on the inside surface of the vesicle