BIOL 3000 Exam 3 Questions And Answers
2026 Update!!!
movement of ions and molecules in and
Define nuclear transport out of the nucleus into or out of the
cytoplasm
rRNA + ribosomal proteins (that were
transported in) → form ribosomal
subunits needed for translation in the
cytoplasm
What generally moves out of the nucleus into transcription of rRNA and
the cytoplasm? formation of ribosomal subunits
occurs in the nucleolus
mRNA that was transcribed in the
nucleus
tRNA
translated, complete ribosomal proteins
(to form subunits in the nucleolus)
What generally moves out of the cytoplasm into proteins needed for transcription of DNA
the nucleus into tRNA, rRNA, and mRNA
proteins needed for chromosome
replication
,Nuclear structure nucleoplasm w/ DECONDENSED
chromatin (allows for transcription and
replication)
nucleolus (ribosomal synthesis)
membranous structure = nucleus is
surrounded by a nuclear envelope
(DOUBLE membrane structure)
inner nuclear membrane (lipid
bilayer) — perinuclear space —
outer nuclear membrane (lipid
bilayer)
connection to the ER
perinuclear space is contiguous
with the lumen of the ER
, nuclear envelope is thus a
projection of the ER
ribosomes on the outer nuclear
membrane are co-translationally
inserting newly synthesized
polypeptides into the perinuclear
space (like RER membrane &
lumen)
nuclear lamina
layer of fibers/lamin proteins
under the inner membrane
nuclear pores
1000s per nuclear envelope, 60-
70nm in width
passageways for materials to go
in and out of nucleus
“zone of exclusion” on nuclear
side of the pore with no material
around the NPC
octagonal symmetry
8 subunits on cytoplasmic side =
passageways for small molecules
fishnet/fish basket on
Nuclear pore complex composition nucleoplasmic side sorting cargo
9th unit in the middle = transporter for
large objects
intrinsically disordered proteins on the
inside of the transporter channel
Ion/small molecules vs large molecule transport ions and small molecules = non-
through NPC selective passive transport: free
movement through any subunit
passageway
move down their concentration
gradients
molecules must be less than
10nm in diameter, <40kDa
larger molecules = selective indirect
active transport
indirect: molecules moving down
their concentration gradients
provide free energy
, active: hydrolysis of GTP
nucleotides required
selective: not all large molecules
can enter
molecules must be 10-30nm in
diameter, >40kDa
central channel of NPC can dilate to
~30nm
experiment
coated gold particles with
proteins known to enter/be
located in the nucleus (gold
deflects electrons → dark in EM)
gold particles 22nm and 26nm in
diameter were found in
cytoplasm and nucleoplasm
(entered the nucleus)
How large can objects be before it stops gold particles 36nm in diameter
entering the nucleus? were not present in the
nucleoplasm
gold particles only congregated
at some regions of the nuclear
envelope (only moving through
nuclear pore complexes
viruses
larger viruses, although they
can’t actually enter the nucleus,
can bind and sit on the NPC and
inject its nucleic acid sequence
into the nucleus
nuclear localization signal; 20-30 amino
acids in length → needed to enter
nucleus
filled with basic residues (like
Arginine [Arg, R] and Lysine [Lys,
What signal on a protein allows for nuclear K])
import? without the NLS, the protein will be free
floating in the cytoplasm = will not enter
the nucleus! proven with fluorescent
tracking of proteins
need importin protein = receptor
for NLS
2026 Update!!!
movement of ions and molecules in and
Define nuclear transport out of the nucleus into or out of the
cytoplasm
rRNA + ribosomal proteins (that were
transported in) → form ribosomal
subunits needed for translation in the
cytoplasm
What generally moves out of the nucleus into transcription of rRNA and
the cytoplasm? formation of ribosomal subunits
occurs in the nucleolus
mRNA that was transcribed in the
nucleus
tRNA
translated, complete ribosomal proteins
(to form subunits in the nucleolus)
What generally moves out of the cytoplasm into proteins needed for transcription of DNA
the nucleus into tRNA, rRNA, and mRNA
proteins needed for chromosome
replication
,Nuclear structure nucleoplasm w/ DECONDENSED
chromatin (allows for transcription and
replication)
nucleolus (ribosomal synthesis)
membranous structure = nucleus is
surrounded by a nuclear envelope
(DOUBLE membrane structure)
inner nuclear membrane (lipid
bilayer) — perinuclear space —
outer nuclear membrane (lipid
bilayer)
connection to the ER
perinuclear space is contiguous
with the lumen of the ER
, nuclear envelope is thus a
projection of the ER
ribosomes on the outer nuclear
membrane are co-translationally
inserting newly synthesized
polypeptides into the perinuclear
space (like RER membrane &
lumen)
nuclear lamina
layer of fibers/lamin proteins
under the inner membrane
nuclear pores
1000s per nuclear envelope, 60-
70nm in width
passageways for materials to go
in and out of nucleus
“zone of exclusion” on nuclear
side of the pore with no material
around the NPC
octagonal symmetry
8 subunits on cytoplasmic side =
passageways for small molecules
fishnet/fish basket on
Nuclear pore complex composition nucleoplasmic side sorting cargo
9th unit in the middle = transporter for
large objects
intrinsically disordered proteins on the
inside of the transporter channel
Ion/small molecules vs large molecule transport ions and small molecules = non-
through NPC selective passive transport: free
movement through any subunit
passageway
move down their concentration
gradients
molecules must be less than
10nm in diameter, <40kDa
larger molecules = selective indirect
active transport
indirect: molecules moving down
their concentration gradients
provide free energy
, active: hydrolysis of GTP
nucleotides required
selective: not all large molecules
can enter
molecules must be 10-30nm in
diameter, >40kDa
central channel of NPC can dilate to
~30nm
experiment
coated gold particles with
proteins known to enter/be
located in the nucleus (gold
deflects electrons → dark in EM)
gold particles 22nm and 26nm in
diameter were found in
cytoplasm and nucleoplasm
(entered the nucleus)
How large can objects be before it stops gold particles 36nm in diameter
entering the nucleus? were not present in the
nucleoplasm
gold particles only congregated
at some regions of the nuclear
envelope (only moving through
nuclear pore complexes
viruses
larger viruses, although they
can’t actually enter the nucleus,
can bind and sit on the NPC and
inject its nucleic acid sequence
into the nucleus
nuclear localization signal; 20-30 amino
acids in length → needed to enter
nucleus
filled with basic residues (like
Arginine [Arg, R] and Lysine [Lys,
What signal on a protein allows for nuclear K])
import? without the NLS, the protein will be free
floating in the cytoplasm = will not enter
the nucleus! proven with fluorescent
tracking of proteins
need importin protein = receptor
for NLS
