Membrane Proteins and Structure Quiz

<p>20-30 (A)</p> Signup and view all the answers

<p>All of the above. (D)</p> Signup and view all the answers

<p>The hydrophobicity of beta-barrel proteins is not as pronounced, requiring fewer residues to span the membrane. (C)</p> Signup and view all the answers

<p>They are typically comprised of 3.6 amino acid residues per turn. (A)</p> Signup and view all the answers

<p>It identifies regions of a protein that are likely to be embedded within the membrane due to their hydrophobicity. (B)</p> Signup and view all the answers

<p>Interaction with proteins on the surface of another cell (A), Aggregation of proteins within the membrane (B), Association with peripheral membrane components – extrinsic proteins and polysaccharides (C), All of the above (D)</p> Signup and view all the answers

<p>To direct the protein to its final destination within the cell (A)</p> Signup and view all the answers

<p>Vesicular transport (C)</p> Signup and view all the answers

<p>The protein unfolds and translocates through the membrane, followed by refolding after translocation (A)</p> Signup and view all the answers

<p>Mitochondrion (C)</p> Signup and view all the answers

<p>To regulate the passage of molecules between the nucleus and cytoplasm (D)</p> Signup and view all the answers

<p>Lysosome (A)</p> Signup and view all the answers

<p>Proteins carry a signal sequence that directs them to their specific destination (B)</p> Signup and view all the answers

<p>The lack of an oxidizing environment in the cytosol inhibits disulfide bond formation. (C)</p> Signup and view all the answers

<p>Geranylgeranylation (A), Farnesylation (C)</p> Signup and view all the answers

<p>Farnesylation or geranylgeranylation (C)</p> Signup and view all the answers

<p>Regulation of protein folding (C)</p> Signup and view all the answers

<p>Disulfide bridges increase protein stability by reducing flexibility and promoting proper folding. (D)</p> Signup and view all the answers

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

<p>The hydrophilic regions of the protein would have to traverse the hydrophobic core of the lipid bilayer. (C)</p> Signup and view all the answers

<p>Farnesylation or geranylgeranylation (D)</p> Signup and view all the answers

<p>The SRP contains a binding pocket that preferentially binds hydrophobic sequences. (C)</p> Signup and view all the answers

<p>The SRP binds to the large subunit of the ribosome, blocking the binding of the next tRNA. (B)</p> Signup and view all the answers

<p>GTP hydrolysis releases the SRP from the ribosome and the SRP receptor from the translocon. (D)</p> Signup and view all the answers

<p>The Sec-translocon provides a channel for the nascent polypeptide to cross the ER membrane. (A)</p> Signup and view all the answers

<p>The hydrophobic region ensures that the signal peptide is recognized by the SRP. (C)</p> Signup and view all the answers

<p>The SRP receptor binds to the SRP and delivers the ribosome to the ER membrane. (C)</p> Signup and view all the answers

<p>It ensures that the signal sequence is properly targeted to the ER membrane. (C)</p> Signup and view all the answers

<p>The stalling allows for the SRP to bind to the SRP receptor and deliver the ribosome to the ER membrane. (B)</p> Signup and view all the answers

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

<p>The Sec61/SecY translocon is a passive pore, while the SRP receptor is an active transporter. (C)</p> Signup and view all the answers

<p>Type I membrane-bound proteins. (A)</p> Signup and view all the answers

<p>Type II and multi-spanning proteins are targeted by their transmembrane domains, while type I proteins are targeted by their signal peptides. (C)</p> Signup and view all the answers

<p>To halt translocation and release the polypeptide chain into the membrane. (A)</p> Signup and view all the answers

<p>It is a highly conserved heterotrimeric membrane complex. (A)</p> Signup and view all the answers

<p>Co-translational translocation occurs before protein synthesis is complete, while post-translational translocation occurs after protein synthesis is complete. (C)</p> Signup and view all the answers

<p>It is composed of a single polypeptide chain. (D)</p> Signup and view all the answers

<p>BiP acts as a molecular ratchet, preventing the polypeptide from backtracking through the Sec61 channel. (A)</p> Signup and view all the answers

<p>Prokaryotic translocation is driven by an electrochemical gradient across the membrane, while eukaryotic translocation is primarily driven by ATP hydrolysis. (D)</p> Signup and view all the answers

<p>They act as a signal for the SRP to bind to the ribosome, stalling translation. (D)</p> Signup and view all the answers

<p>The Sec pathway transports folded proteins, while the Tat pathway transports unfolded. (B)</p> Signup and view all the answers

<p>Signal sequence at the N-terminus, stop-transfer sequence at the C-terminus. (D)</p> Signup and view all the answers

<p>Archaea have evolved alternative, yet less understood, protein translocation systems. (C)</p> Signup and view all the answers

<p>Membrane proteins are crucial for cell signaling, nutrient transport, and maintaining cellular shape. (D)</p> Signup and view all the answers

Proteins attached to the membrane through non-covalent interactions with other proteins.

A right-handed helical structure in proteins with 3.6 amino acid residues per turn.

A common secondary structure in proteins formed by hydrogen bonds between different strands.

Graphs used to predict hydrophobic regions in membrane proteins based on sequence analysis.

Chemical bonds that link amino acids in proteins, characterized by polarity and hydrogen bonding.

Visual representations that help identify and analyze the arrangement of amino acids in helical structures.

A segment in proteins that is hydrophobic and spans the membrane, typically 20-30 residues long.

Proteins that form a barrel-like shape with 10 residues required to span the membrane, less predictable than α-helices.

Mechanisms that limit a protein's movement within the membrane.

Grouping of proteins within cellular membranes to restrict movement.

Linkage of proteins to the cell's internal structure to prevent movement.

Protein movement between cytosol and nucleus via nuclear pore complexes.

Transport of proteins in membrane-bound vesicles between compartments.

Movement of proteins across membranes using translocators.

The concept that proteins have signal sequences for destination identification.

A tag on newly synthesized proteins indicating their destination.

The process of transporting and embedding proteins into membranes as they are being synthesized.

A short peptide sequence that directs the transport of a protein to the membrane.

A protein-RNA complex that recognizes and binds the signal peptide to halt translation temporarily.

A protein that binds the SRP, facilitating the docking of the ribosome on the endoplasmic reticulum (ER).

The process that releases the SRP and SRP-receptor from the translocon by converting GTP to GDP.

A channel in the membrane that allows the newly synthesized protein to pass through.

The variety of sequences present in ER signal peptides, typically containing non-polar amino acids.

The flexible area in the SRP that accommodates various hydrophobic sequences from unfolded polypeptides.

A highly conserved membrane complex that forms a pore for protein translocation.

Sec61/SecY allows molecules to pass but requires energy from active transport for function.

Movement of polypeptides across membranes occurs while they are being synthesized.

The N-terminal signal sequence that initiates the transport of a protein through Sec61/SecY.

A second hydrophobic sequence that halts the transport of a protein through Sec61/SecY.

Proteins that are inserted into a membrane with a single N-terminal segment.

The Sec61/SecY complex consists of α, β, and γ subunits forming a central pore.

A protein modification involving the addition of a farnesyl group, usually at the C-terminus.

A lipid modification where a geranylgeranyl group is added to proteins, also primarily at the C-terminus.

The process of adding carbohydrates to proteins, mainly found on the exterior of membranes in animal cells.

A carbohydrate-rich layer surrounding the cell membrane, contributing to cell protection and communication.

Covalent bonds formed between cysteine residues in proteins, enhancing stability, especially outside cell environments.

The movement of proteins in the membrane, including lateral diffusion and rotation.

The sideways movement of proteins within the lipid bilayer, happening quickly.

An environment within cells where oxidative bonds, such as disulfide bridges, are less stable due to high levels of reducing agents.

A translocon that facilitates protein translocation into the endoplasmic reticulum.

A Hsp70 family member that helps in the folding of polypeptides during translocation.

An ATP-powered protein that drives polypeptide movement in prokaryotes.

Transports fully folded proteins across membranes using PMF, with TatABC components.

Utilizes the Sec61/SecY translocator to transport unfolded proteins into the endoplasmic reticulum.

A difference in charge and solute concentration across a membrane that drives transport.

Chemical modifications, such as glycosylation and lipid attachments, that alter protein functions.