Cell Physiology Exam 2

An ER localization sequence in a polypeptide chain targets all but … proteins to the rough ER surface.

• Plasma membrane

• Lysosomal

• Secreted

• Mitochondrial

By restricting the traffic of proteins and RNA across the nuclear envelope, eukaryotic cells can regulate … in unique ways.

• Endocytosis

• Translation only

• Translation and transcription

• Transcription only

Cajal bodies are thought to represent sites of:

• large ribosomal subunit assembly.

• small ribosomal subunit assembly.

• DNA replication

• snRNA processing and assembly.

Disulfide bonds within or between proteins form easily:

• in the ER but not the cytosol.

• in both the cytosol and the ER.

• in neither the cytosol nor the ER.

• in the cytosol but not the ER.

Export of RNAs from the nucleus occurs primarily by:

• Positive diffusion through nuclear pore complexes

• Selective transport through nuclear pore complexes

• Co-transcriptional insertion through protein pores of the nuclear envelope membrane

• Release from the nucleus when it breaks down at mitosis

Free ribosomes in the cytosol and ribosomes bound to the ER membrane have;

• Different types of large subunits but the same small subunits

• Different types of large and subunits

• Different types of small subunits but the same large subunits

• The same types of large and small subunits

GPI-anchored proteins are synthesized:

• On free ribosomes and attached to the GPI group of the systolic surface of the ER

• On free ribosomes and attached to the GPI group on the outside of the ER

• As transmembrane protein, then are cleaved and joined to the GPI group on the cytosolic surface of the ER

• As transmembrane proteins, then are cleaved and joined to the GPI group on the inner (lumenal) surface of the ER

Heterochromatin is normally associated with

• The nuclear envelope

• Mutated chromosomes

• Ribosomes

• Only a few specific human chromosomes

Highly condensed, transcriptionally inactive chromatin is called:

• Euchromatin

• A chromatin domain

• Heterochromatin

• Histone-containing chromatin

If a nuclear protein is stripped of its nuclear localization signal and injected into the cytoplasm of cultured cells, where would you hypothesize the protein will localize?

• In the cytoplasm

• Extracellularly

• In a ring around the outside of the nuclear envelope

• To the nucleus