Cellular Transport Mechanisms Quiz

<p>Export of proteins and ribosomal subunits from the nucleus (B)</p> Signup and view all the answers

<p>Interaction with Ran-GTP (A)</p> Signup and view all the answers

<p>To transport proteins containing nuclear-export signals (NES) out of the nucleus (C)</p> Signup and view all the answers

<p>They shuttle between the nucleus and cytoplasm (B)</p> Signup and view all the answers

<p>Presence of GEF inducing GDP release (B)</p> Signup and view all the answers

<p>They accelerate the hydrolysis of GTP to GDP, inactivating the proteins (C)</p> Signup and view all the answers

<p>It exists in different conformations when bound to GTP or GDP (D)</p> Signup and view all the answers

<p>Nonsecretory pathway (B)</p> Signup and view all the answers

<p>Direct proteins to specific organelles (C)</p> Signup and view all the answers

<p>Peroxisomes and chloroplasts (D)</p> Signup and view all the answers

<p>ATP hydrolysis (D)</p> Signup and view all the answers

<p>Location of synthesis (B)</p> Signup and view all the answers

<p>Bind and transfer polypeptides to translocation channels (B)</p> Signup and view all the answers

<p>They are translocated across the membrane into the organelle’s interior. (A)</p> Signup and view all the answers

<p>20-50 amino acids (A)</p> Signup and view all the answers

<p>It cannot inhibit elastase, resulting in elastin destruction. (A)</p> Signup and view all the answers

<p>To direct cytosolic proteins to the mitochondrion. (A)</p> Signup and view all the answers

<p>In an unfolded state using the proton-motive force. (C)</p> Signup and view all the answers

<p>They must be in a folded state and contain a specific targeting sequence. (C)</p> Signup and view all the answers

<p>To help translocate proteins into the mitochondrial matrix. (B)</p> Signup and view all the answers

<p>Tom40 and Tim44. (A)</p> Signup and view all the answers

<p>They are single-membrane organelles containing oxidases and catalase. (A)</p> Signup and view all the answers

<p>C-terminal PTS1 or N-terminal PTS2. (D)</p> Signup and view all the answers

<p>They help stabilize tertiary and quaternary structures. (A)</p> Signup and view all the answers

<p>Protein Disulfide Isomerase (PDI) (C)</p> Signup and view all the answers

<p>Secretory proteins and exoplasmic domains of membrane proteins (C)</p> Signup and view all the answers

<p>Accumulation of unfolded proteins within the lumen (A)</p> Signup and view all the answers

<p>Calreticulin (D)</p> Signup and view all the answers

<p>Loss of elastin, a structural protein in the lungs (C)</p> Signup and view all the answers

<p>Hac1 (B)</p> Signup and view all the answers

<p>Accelerating rotation about peptidyl-prolyl bonds (B)</p> Signup and view all the answers

<p>To target the ribosome to the ER membrane (D)</p> Signup and view all the answers

<p>To facilitate the transport of proteins across the ER membrane (D)</p> Signup and view all the answers

<p>Membrane-bound and secretory proteins (A)</p> Signup and view all the answers

<p>Binding of the SRP-ribosome complex (A)</p> Signup and view all the answers

<p>Some eukaryotes, like yeast (C)</p> Signup and view all the answers

<p>They contain a cleavable N-terminal signal sequence and stop-transfer anchor (C)</p> Signup and view all the answers

<p>Type IV A has its N-terminus in the cytosol; Type IV B in the exoplasmic face (C)</p> Signup and view all the answers

<p>Proteolytic cleavages for activation (D)</p> Signup and view all the answers

<p>It assists in cellular signaling and recognition (C)</p> Signup and view all the answers

<p>Sec63 complex (B)</p> Signup and view all the answers

<p>Proteins anchored by glycosylphosphatidylinositol (D)</p> Signup and view all the answers

<p>The orientation and arrangement of membrane-spanning segments (A)</p> Signup and view all the answers

<p>Potential energy from the protein's hydrophobic regions (B)</p> Signup and view all the answers

The process by which proteins are directed to their correct location within a cell, such as the cytosol, organelles, or the plasma membrane.

A short sequence of amino acids (typically 20-50) within a protein that acts as a postal code, guiding it to its specific destination within the cell.

The two main pathways are the nonsecretory pathway and the secretory pathway. The nonsecretory pathway targets proteins to organelles such as the cytosol, peroxisomes, mitochondria, chloroplasts, and the nucleus. The secretory pathway targets proteins to the plasma membrane, ER, Golgi apparatus, lysosomes, and for export from the cell.

This pathway directs proteins synthesized on free ribosomes to organelles like the cytosol, peroxisomes, mitochondria, chloroplasts, and the nucleus.

This pathway targets proteins synthesized on bound ribosomes to the plasma membrane, ER, Golgi apparatus, lysosomes, or for export from the cell.

Each signal sequence has a specific amino acid sequence that distinguishes it from other signal sequences. This uniqueness allows for specific recognition by receptors within the cell.

The signal sequence binds to a receptor on the target organelle, and this binding triggers the protein's translocation across the organellar membrane.

The protein is guided through a translocation channel in the membrane. This process is often coupled to an energy-consuming process, such as ATP hydrolysis.

The process of protein translocation across the ER membrane that occurs while the protein is still being synthesized.

A protein-RNA complex that binds to the ER signal sequence and helps guide the ribosome to the ER membrane.

An integral membrane protein in the ER membrane that binds to the SRP and anchors the ribosome.

A protein channel in the ER membrane that allows the polypeptide chain to translocate across the membrane.

The process of protein translocation across the ER membrane that occurs after the protein has been fully synthesized.

A protein complex that forms the translocon channel in the ER membrane.

Short amino acid sequences within a protein that determine its orientation and localization within the ER membrane.

A single-pass membrane protein with its N-terminus in the exoplasmic face and C-terminus in the cytosol.

A single-pass membrane protein with its N-terminus in the cytosol and C-terminus in the exoplasmic face.

A single-pass membrane protein with its N-terminus in the exoplasmic face and C-terminus in the cytosol, similar to Type I but lacks a cleavable signal sequence.

A multi-pass membrane protein that crosses the phospholipid bilayer multiple times.

A protein anchored to the membrane by a glycosylphosphatidylinositol (GPI) molecule.

The addition of carbohydrate groups to proteins.

An enzyme found in the ER lumen of eukaryotic cells that catalyzes the formation and rearrangement of disulfide bonds in proteins.

Covalent bonds between cysteine residues that help stabilize the tertiary and quaternary structures of proteins. They are only found in proteins that pass through the ER lumen.

Carbohydrate-binding proteins that bind to N-linked glycosylated proteins in the ER lumen, facilitating proper folding. Examples include calnexin and calreticulin.

Enzymes that accelerate the rotation around peptidyl-prolyl bonds in unfolded segments of proteins, assisting in proper folding.

A cellular stress response triggered by the accumulation of misfolded proteins in the ER lumen. It leads to increased synthesis of chaperones and other proteins that assist in folding.

An ER membrane protein that plays a key role in the unfolded protein response. It activates the transcription of genes encoding proteins that assist in folding.

A transcription factor activated during the unfolded protein response. It promotes the transcription of genes encoding protein-folding catalysts.

A genetic disease caused by a misfolded protein, alpha-1-antitrypsin (AAT). This misfolding leads to a deficiency in the lung structural protein, elastin.

A short amino acid sequence, often near a protein's C-terminus, that directs proteins to the nucleus.

A transport protein that binds to the NLS and carries a cargo protein into the nucleus.

Once inside the nucleus, importin interacts with Ran-GTP, causing a conformational change that lowers its affinity for the NLS, leading to the release of the cargo protein.

Similar mechanism used to export proteins, tRNAs, and ribosomal subunits from the nucleus to the cytoplasm.

Ran-GTP is involved in the release of cargo inside the nucleus, while Ran-GDP is involved in the release of cargo outside the nucleus.

Mutant AAT can't inhibit elastase, which breaks down elastin. This leads to the destruction of elastin, causing damage to tissues.

Wild type AAT inhibits both trypsin and elastase, enzymes responsible for breaking down proteins.

Misfolded proteins are exported to the cytosol through the translocon and then degraded by the ubiquitin/proteasome pathway.

Most mitochondrial proteins are synthesized on free ribosomes in the cytosol. Some are synthesized on ribosomes within the mitochondrial matrix.

Mitochondrial Targeting Sequence. It's a signal sequence at the N-terminus of mitochondrial proteins, guiding them to the mitochondria.

Mitochondrial import requires an actively respiring mitochondrion with a proton-motive force, and unfolded proteins.

Single-membrane bound organelles containing oxidases and catalase, involved in various metabolic processes.

Peroxisomal Targeting Sequence. It's a C-terminal signal sequence found on most peroxisomal proteins, containing the SKL motif.

A short amino acid sequence within a protein that signals for its transport out of the nucleus.

A GTP-bound form of the Ran protein that is required for exportin to bind to cargo proteins and facilitate their nuclear export.

The NES sequence within a cargo protein interacts with the exportin protein. The binding of exportin to the NES is facilitated by the presence of Ran-GTP.

Ran-GTP is hydrolyzed to Ran-GDP, which weakens the exportin-cargo complex, leading to their dissociation.