Alberts Molecular Biology of Cell - Chapter 005 Test Quiz Bank With Questions & Answers 2023/2024
Cytoplasmcorrect answers Contents of a cell that are
... [Show More] contained within its plasma membrane but, in the case of eukaryotic cells, outside the nucleus
Cytosolcorrect answers Contents of the main compartment of the cell, excluding the nucleus and membrane bounded compartments such as ER and mitochondria. the main site of protein degradation
Gated transportcorrect answers Movement of proteins through nuclear pore complexes between the
cytosol and the nucleus.
Organellecorrect answers Membrane-enclosed compartment in a eukaryotic cell that has a distinct
structure, macromolecular composition, and function.
Signal sequencecorrect answers Protein sorting signal that consists of a short continuous sequence of
amino acids.
TRUE OR FALSE
The biological membranes that partition the cell into functionally distinct
compartments are impermeable.correct answers FALSE
lipid bilayers themselves are impermeable to hydrophilic molecules but biological membranes, which contain proteins in addition to the bilayer are not. they are selectively permeable
TRUE OR FALSE
Like the lumen of the endoplasmic reticulum (ER), the interior of the
nucleus is topologically equivalent to the outside of the cell.correct answers FALSE
the nucleus is topologically equivalent to the cytoplasm because the outer and inner membrane are continuous with one another
TRUE OR FALSE
ER-bound and free ribosomes, which are structurally and functionally
identical, differ only in the proteins they happen to be making at a particular
time.correct answers TRUE
Ribosomes all begin translating mRNAs in the cytosol. the mRNAs for certain proteins encode a signal sequence for the ER membrane. after synthesis, the nascent protein along with the ribosome and the mRNA is directed by the signal sequence to the ER membrane. Ribosomes translating mRNA without such a sequence remain free in the cytosol
TRUE or FALSE
Each signal sequence specifies a particular destination in the cell.correct answers TRUE
Signal sequences that specify particular cellular destinations have characteristic features that allow their interaction with appropriate sorting receptors, which guide them to their target compartment
Is it really true that all human cells contain the same basic set of membrane-
enclosed organelles? Do you know of any examples of human cells
that do not have a complete set of organelles?correct answers The vast majority of cells in the human body do have a complete set of membrane enclosed organelles. Certain specialised cells do not. e.g. Red Blood Cell. only a plasma membrane enclosed cytosol
Cells that make up the lens of the eye lack a mitochondria
Why do eukaryotic cells require a nucleus as a separate compartment
when prokaryotic cells manage perfectly well without?correct answers Eukaryotic gene expression is more complicated. Prokaryotic cells do not have introns that interrupt the coding sequences on their genes, so that an mRNA can be translated immediately after transcription. In eukaryotic cells most RNA transcripts must be spliced before translation. The nuclear envelope separates the transcription and translation processes in space and time.
What is the fate of a protein with no sorting signal?correct answers The protein will remain in the cytosol
Which
type of protein synthesis—in the cytosol or on the ER—do you think is
responsible for the majority of protein synthesis in a liver cell?correct answers In cells that do not secrete large amounts of protein, the majority of protein synthesis is likely to occur in the cytosol.
List the organelles in an animal cell that obtain their proteins via gated
transport, via transmembrane transport, or via vesicular transport.correct answers The nucleus is the only organelle that receives its proteins by gated transport.
The ER mitochondria and peroxisomes all receive their proteins by transmembrane transport, mediated by specific protein translocators that reside in the membrane
The golgi apparatus, secretory vesicles, early and late endosome and lysosomes all obtain their proteins via vesicular transport
Nuclear export signalcorrect answers Sorting signal contained in the structure of macromolecules and complexes
that are transported from the nucleus to the cytosol through
nuclear pore complexes.
Nuclear Pore Complex (NPC)correct answers Large multiprotein structure forming a channel through the nuclear
envelope that allows selected molecules to move between nucleus and
cytoplasm. It has a nuclear basket and each NPC contains aqueous passages, through which small water soluble molecules can diffuse passively
How does selective import into the nucleus occur?correct answers The nuclear localization signal (NLS) are responsible for the selectivity of the active nuclear import process.
To initiate nuclear import, most. NLS must be recognized by nuclear import receptors that are sometimes called importins , export requires exportins. Importins and exportins belong to the karypherin family.
The importin finds the nuclear pore complex via FG repeats of the nucleoporins, of which there are 30 form the npc.
FG for phenylalanine and glycine
Rancorrect answers Monomeric GTPase present in both cytosol and nucleus that is required
for the active transport of macromolecules into and out of the nucleus [Show Less]