Mastering Biology 7.4-7.5 Flashcards

Which molecules do not normally cross the nuclear membrane?

Which of the following statements about the nuclear envelope is false?

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

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?

In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules?

Which of the following conclusions can be drawn from the results of injecting fusion proteins into a cell?

What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?

How are these signals read?

Which statement most accurately describes what happens to proteins that lack an ER signal sequence?

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?

Nuclear Transport and Proteins

DNA does not normally cross the nuclear membrane, whereas RNA and proteins can.
A false statement about the nuclear envelope is that it is continuous with the Golgi apparatus; it consists of two lipid bilayers and has nuclear pores for molecule transport.
Large proteins with a nuclear localization signal (NLS) require energy to bind to the nuclear pore for entry into the nucleus; thus, the statement that they enter without energy expenditure is false.
A small protein of 25,000 daltons can enter the nucleus via passive transport, which does not require energy.

Labeling and Fusion Proteins

Fluorescent labeling of proteins in experiments allows for easier visualization rather than increasing size or providing energy.
Nucleoplasmin, when divided and fused with a cytoplasmic protein, demonstrated that only one of the fusion proteins contains a nuclear localization signal.

Secretion Pathway for Newly Synthesized Proteins

Newly synthesized proteins destined for secretion typically follow the pathway: ER → Golgi → vesicles that fuse with the plasma membrane.
Signals that guide the proteins through the secretion pathway achieve their function by binding to receptor proteins.

Proteins without ER Signal Sequences

Proteins lacking an ER signal sequence are released into the cytosol rather than entering the ER or Golgi apparatus.

Receptor-Mediated Endocytosis

In receptor-mediated endocytosis, receptor molecules that initially face outward end up on the inside surface of the vesicle after the process concludes.

Test your knowledge on the topics from Biology chapters 7.4 and 7.5 with these flashcards. This quiz will cover key concepts about the nuclear membrane and envelope, including what molecules can cross and the structure of nuclear pores. Perfect for review and mastery of important biological concepts.