BIO 353 Chen Exam 2 Questions And Answers With
Verified Study Solutions
endomembrane system ANS A network of membranes inside and around a eukaryotic cell,
related either through direct physical contact or by the transfer of membranous vesicles.
Nuclear envelope, ER, GA, Lysosome, Vesicles, Endosomes, PM (plasma membrane)
Two types of Protein Synthesis ANS From free polyribosomes in cytosol
From membrane-bound polyribosomes
Polyribosome ANS a mRNA that has multiple ribosomes on it progressing from 5' to 3' end
Synthesis from free polyribosomes ANS -Makes proteins floating freely in cytosol
-Does NOT make transmembrane proteins nor proteins destined for exocytosis
Synthesis from membrane-bound polyribosomes ANS -Makes membrane associated proteins &
proteins in endomembrane vesicles
-Present only in Eukaryotic cells
Universal retention sequence for Er ANS -Lys-Asp-Glu -Leu-COO-
KDEL
How are proteins directed to target organelles? ANS Sorting signals
Where do proteins with no sorting signal go? ANS Stay in cytosol
Proteins needed in nucleus ANS -soluble proteins that associate with DNA
,How does nuclear envelope get lipids and membrane proteins? ANS ER membrane is contiguous
w/ nuclear envelope, so
lipids and membrane proteins synthesized in ER can be transported via backfilling (aka lateral
movement_ along lipid layers
Nuclear Pore ANS Large structures on nuclear envelope
-Inner meshwork made short repeated sequences called FGs of pore proteins which prevent the
passage of large molecules (lets in small hydrophilic ones)
-Protein fibrils protrude on both sides (cytosolic & nuclear). Form tentacles on cytosol and a basket
on nucleus
How does nucleus get soluble proteins for DNA? ANS Proteins are transported post-
translationally from cytosol (meaning in full functional form) through nuclear pores
What do proteins destined for nucleus have? And what are the two functions of this thing? ANS
A sorting signal called a nuclear localization signal (NLS) which serves as both a mailing address to
the nucleus and a ticket in
What are NLSs recognized by? ANS Nuclear import receptors (NIRs) aka IMPORTIN
Importin ANS Nuclear import receptor (NIR)
How is protein import into nucleus accomplished? ANS -NLS on cargo protein recognized by
NIR which attach to cause conformational change in complex which results in high affinity to
nuclear pore tentacles in cytosol which pulls complex into the pore
-NIR grabs onto FG repeats and bounce from FG to FG, plowing way into nucleus
-Attract to basket to enter nucleus, NIR and cargo protein dissociate and cargo protein is delivered
Ran ANS GTPase (has GTP on it) that can cause conformational changes essential for
translocation of protein through the NPC
, Ran-GAP ANS Ran-GAP (GTPase Activating Protein) helps convert Ran GTP to Ran GDP via
hydrolysis
What is on protein needing to leave the nucleus ANS Nuclear export signal (NES)
What attaches to NES? ANS Nuclear export receptor (NER) aka exportin
Exportin ANS nuclear export receptor
How does NIR detach from cargo protein once inside the nucleus? ANS Ran attaches, cargo
protein yeets off
NIR-Ran complex is transferred back to cytosol
How does protein export from nucleus work in regard to Ran? ANS Ran needs to complex to
protein and NES before it can move out. Once it moves out, Ran is yeeted off to deliver the protein
How are Ran and importin/exportin recycled once in the cytosol? ANS Ran GAP hydrolyzes to
make GTP into GDP, separating everything to be reused
How is Ran GTP replenished on nuclear side if both import and export of cargo proteins end up with
Ran GDP on cytosolic side? ANS Has a specialized import receptor to get into the nucleus called
nuclear transport factor 2 (NTF2)
NTF2 ANS binds Ran GDP and transports it to the nucleus
Is itself reused and transferred back into the cytosol by passive diffusion as it is small
Protein Transport into Mitochondria and Chloroplasts ANS Protein from cytosol transferred w/
post-translational transport
Mitochondria & Chloroplasts are double membraned, requiring two layers of membrane to be
bypassed for delivery
Verified Study Solutions
endomembrane system ANS A network of membranes inside and around a eukaryotic cell,
related either through direct physical contact or by the transfer of membranous vesicles.
Nuclear envelope, ER, GA, Lysosome, Vesicles, Endosomes, PM (plasma membrane)
Two types of Protein Synthesis ANS From free polyribosomes in cytosol
From membrane-bound polyribosomes
Polyribosome ANS a mRNA that has multiple ribosomes on it progressing from 5' to 3' end
Synthesis from free polyribosomes ANS -Makes proteins floating freely in cytosol
-Does NOT make transmembrane proteins nor proteins destined for exocytosis
Synthesis from membrane-bound polyribosomes ANS -Makes membrane associated proteins &
proteins in endomembrane vesicles
-Present only in Eukaryotic cells
Universal retention sequence for Er ANS -Lys-Asp-Glu -Leu-COO-
KDEL
How are proteins directed to target organelles? ANS Sorting signals
Where do proteins with no sorting signal go? ANS Stay in cytosol
Proteins needed in nucleus ANS -soluble proteins that associate with DNA
,How does nuclear envelope get lipids and membrane proteins? ANS ER membrane is contiguous
w/ nuclear envelope, so
lipids and membrane proteins synthesized in ER can be transported via backfilling (aka lateral
movement_ along lipid layers
Nuclear Pore ANS Large structures on nuclear envelope
-Inner meshwork made short repeated sequences called FGs of pore proteins which prevent the
passage of large molecules (lets in small hydrophilic ones)
-Protein fibrils protrude on both sides (cytosolic & nuclear). Form tentacles on cytosol and a basket
on nucleus
How does nucleus get soluble proteins for DNA? ANS Proteins are transported post-
translationally from cytosol (meaning in full functional form) through nuclear pores
What do proteins destined for nucleus have? And what are the two functions of this thing? ANS
A sorting signal called a nuclear localization signal (NLS) which serves as both a mailing address to
the nucleus and a ticket in
What are NLSs recognized by? ANS Nuclear import receptors (NIRs) aka IMPORTIN
Importin ANS Nuclear import receptor (NIR)
How is protein import into nucleus accomplished? ANS -NLS on cargo protein recognized by
NIR which attach to cause conformational change in complex which results in high affinity to
nuclear pore tentacles in cytosol which pulls complex into the pore
-NIR grabs onto FG repeats and bounce from FG to FG, plowing way into nucleus
-Attract to basket to enter nucleus, NIR and cargo protein dissociate and cargo protein is delivered
Ran ANS GTPase (has GTP on it) that can cause conformational changes essential for
translocation of protein through the NPC
, Ran-GAP ANS Ran-GAP (GTPase Activating Protein) helps convert Ran GTP to Ran GDP via
hydrolysis
What is on protein needing to leave the nucleus ANS Nuclear export signal (NES)
What attaches to NES? ANS Nuclear export receptor (NER) aka exportin
Exportin ANS nuclear export receptor
How does NIR detach from cargo protein once inside the nucleus? ANS Ran attaches, cargo
protein yeets off
NIR-Ran complex is transferred back to cytosol
How does protein export from nucleus work in regard to Ran? ANS Ran needs to complex to
protein and NES before it can move out. Once it moves out, Ran is yeeted off to deliver the protein
How are Ran and importin/exportin recycled once in the cytosol? ANS Ran GAP hydrolyzes to
make GTP into GDP, separating everything to be reused
How is Ran GTP replenished on nuclear side if both import and export of cargo proteins end up with
Ran GDP on cytosolic side? ANS Has a specialized import receptor to get into the nucleus called
nuclear transport factor 2 (NTF2)
NTF2 ANS binds Ran GDP and transports it to the nucleus
Is itself reused and transferred back into the cytosol by passive diffusion as it is small
Protein Transport into Mitochondria and Chloroplasts ANS Protein from cytosol transferred w/
post-translational transport
Mitochondria & Chloroplasts are double membraned, requiring two layers of membrane to be
bypassed for delivery
