BIO 353 - Chen Exam 2 Questions and
Answers 100% Pass
endomembrane system - ✔✔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 - ✔✔From free polyribosomes in cytosol
From membrane-bound polyribosomes
Polyribosome - ✔✔a mRNA that has multiple ribosomes on it progressing from 5' to 3'
end
Synthesis from free polyribosomes - ✔✔-Makes proteins floating freely in cytosol
-Does NOT make transmembrane proteins nor proteins destined for exocytosis
Synthesis from membrane-bound polyribosomes - ✔✔-Makes membrane associated
proteins & proteins in endomembrane vesicles
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,-Present only in Eukaryotic cells
Universal retention sequence for Er - ✔✔-Lys-Asp-Glu -Leu-COO-
KDEL
How are proteins directed to target organelles? - ✔✔Sorting signals
Where do proteins with no sorting signal go? - ✔✔Stay in cytosol
Proteins needed in nucleus - ✔✔-soluble proteins that associate with DNA
How does nuclear envelope get lipids and membrane proteins? - ✔✔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 - ✔✔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? - ✔✔Proteins are transported post-
translationally from cytosol (meaning in full functional form) through nuclear pores
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, What do proteins destined for nucleus have? And what are the two functions of this
thing? - ✔✔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? - ✔✔Nuclear import receptors (NIRs) aka IMPORTIN
Importin - ✔✔Nuclear import receptor (NIR)
How is protein import into nucleus accomplished? - ✔✔-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 - ✔✔GTPase (has GTP on it) that can cause conformational changes essential for
translocation of protein through the NPC
Ran-GAP - ✔✔Ran-GAP (GTPase Activating Protein) helps convert Ran GTP to Ran
GDP via hydrolysis
What is on protein needing to leave the nucleus - ✔✔Nuclear export signal (NES)
What attaches to NES? - ✔✔Nuclear export receptor (NER) aka exportin
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Answers 100% Pass
endomembrane system - ✔✔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 - ✔✔From free polyribosomes in cytosol
From membrane-bound polyribosomes
Polyribosome - ✔✔a mRNA that has multiple ribosomes on it progressing from 5' to 3'
end
Synthesis from free polyribosomes - ✔✔-Makes proteins floating freely in cytosol
-Does NOT make transmembrane proteins nor proteins destined for exocytosis
Synthesis from membrane-bound polyribosomes - ✔✔-Makes membrane associated
proteins & proteins in endomembrane vesicles
Katelyn Whitman, All Rights Reserved © 2025 1
,-Present only in Eukaryotic cells
Universal retention sequence for Er - ✔✔-Lys-Asp-Glu -Leu-COO-
KDEL
How are proteins directed to target organelles? - ✔✔Sorting signals
Where do proteins with no sorting signal go? - ✔✔Stay in cytosol
Proteins needed in nucleus - ✔✔-soluble proteins that associate with DNA
How does nuclear envelope get lipids and membrane proteins? - ✔✔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 - ✔✔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? - ✔✔Proteins are transported post-
translationally from cytosol (meaning in full functional form) through nuclear pores
Katelyn Whitman, All Rights Reserved © 2025 2
, What do proteins destined for nucleus have? And what are the two functions of this
thing? - ✔✔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? - ✔✔Nuclear import receptors (NIRs) aka IMPORTIN
Importin - ✔✔Nuclear import receptor (NIR)
How is protein import into nucleus accomplished? - ✔✔-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 - ✔✔GTPase (has GTP on it) that can cause conformational changes essential for
translocation of protein through the NPC
Ran-GAP - ✔✔Ran-GAP (GTPase Activating Protein) helps convert Ran GTP to Ran
GDP via hydrolysis
What is on protein needing to leave the nucleus - ✔✔Nuclear export signal (NES)
What attaches to NES? - ✔✔Nuclear export receptor (NER) aka exportin
Katelyn Whitman, All Rights Reserved © 2025 3
