Protein Modification in the ER

What triggers the synthesis of chaperones and other quality control proteins?

Accumulation of unfolded proteins in the ER (correct)
Reduced demand for protein folding
Increase in protein synthesis rate
Depletion of cholesterol in the ER membrane

What is the primary function of the Golgi apparatus in the secretory pathway?

Protein synthesis
Protein degradation
Vesicle formation
Protein modification and sorting (correct)

What determines the size of the ER?

Demand for protein folding (correct)
ER membrane fluidity
Availability of chaperones
Rate of protein synthesis

Which of the following is NOT a function of the secretory pathway?

Protein synthesis (C) Signup and view all the answers

What is the primary function of the cis and trans regions of the Golgi apparatus?

Protein modification and sorting (D) Signup and view all the answers

What is the primary function of chaperone proteins in the ER?

To ensure proper protein folding and prevent misfolding (B) Signup and view all the answers

Which of the following is NOT a consequence of accumulation of misfolded proteins in the ER?

Stimulation of vesicle transport to the plasma membrane (B) Signup and view all the answers

What is the primary function of glycosylation in the ER?

To protect proteins from degradation and guide them to the proper organelle (C) Signup and view all the answers

Where do proteins undergo glycosylation in the secretory pathway?

In the ER lumen (A) Signup and view all the answers

What is the purpose of the unfolded protein response (UPR) in the ER?

To degrade misfolded proteins and maintain ER homeostasis (A) Signup and view all the answers

What is the primary route that proteins follow to reach the Golgi apparatus, endosomes, lysosomes, and the cell surface?

First entering the ER from the cytosol (A) Signup and view all the answers

What happens to water-soluble proteins when they enter the ER?

They cross the ER membrane completely and are released into the lumen (A) Signup and view all the answers

What is the function of the ER in protein trafficking?

To modify and package proteins into vesicles (A) Signup and view all the answers

What is the fate of transmembrane proteins in the ER?

They only partially cross the ER and become embedded in the membrane (B) Signup and view all the answers

What is the common feature of all proteins synthesized by ribosomes in the nucleus?

They are all synthesized by a common pool of ribosomes (C) Signup and view all the answers

What is the role of the signal sequence in directing proteins to the ER?

To open the translocation channel (A) Signup and view all the answers

During protein synthesis, what happens to the signal sequence?

It is recognized by the SRP (C) Signup and view all the answers

What is the function of the SRP?

To recognize and bind to the signal sequence (A) Signup and view all the answers

What happens to proteins that are being synthesized and enter the ER?

They enter the lumen of the ER (A) Signup and view all the answers

What is the role of the signal sequence in transmembrane protein arrangement?

To determine the orientation of the protein in the lipid bilayer (D) Signup and view all the answers

What is the function of signal sequences in protein sorting?

To direct proteins to the correct compartment (D) Signup and view all the answers

What is the mechanism by which proteins enter the nucleus?

Through nuclear pores (B) Signup and view all the answers

What is the term for the process by which a vesicle fuses with the plasma membrane, releasing its contents to the cell's surroundings?

Exocytosis (D) Signup and view all the answers

Which of the following is a destination for proteins that enter the endoplasmic reticulum while being synthesized?

The ER lumen (A) Signup and view all the answers

What is the term for the process by which extracellular materials are captured by vesicles that bud inward from the plasma membrane?

Endocytosis (C) Signup and view all the answers

In which part of the Golgi apparatus does the additional glycosylation and sorting of proteins occur?

Trans face (A) Signup and view all the answers

What is the mechanism by which secretory proteins are released from the cell?

Exocytosis (B) Signup and view all the answers

What is the purpose of the constitutive exocytosis pathway in eukaryotic cells?

To operate continually in all eukaryotic cells (C) Signup and view all the answers

What is the environment of the trans-Golgi network that is essential for the formation of secretory vesicles?

Acidic pH and high calcium concentration (A) Signup and view all the answers

What is the process by which secretory vesicles release their contents in response to a signal?

Vesicle docking and fusion (B) Signup and view all the answers

Where do the bulk of proteins that enter peroxisomes come from?

The cytosol (A) Signup and view all the answers

What is the import signal for proteins entering peroxisomes?

SKL (ser-lys-leu) (B) Signup and view all the answers

What is a consequence of mutations that block peroxisomal protein import?

Zellweger syndrome (D) Signup and view all the answers

How do proteins enter peroxisomes from the cytosol?

Via protein translocators (C) Signup and view all the answers

What is the function of peroxisomal enzymes?

Breakdown of toxins, alcohols, and fatty acids (D) Signup and view all the answers

Do proteins need to unfold to enter peroxisomes?

No, protein translocators allow direct import (C) Signup and view all the answers

Which organelle is involved in protein synthesis and transport?

Endoplasmic reticulum (B) Signup and view all the answers

What is the function of protein receptors in protein transport?

To recognize and bind specific proteins (C) Signup and view all the answers

Which pathway is involved in the transport of proteins from the cytosol to peroxisomes?

Protein targeting pathway (C) Signup and view all the answers

What is the fate of individuals with Zellweger syndrome?

They usually do not survive beyond 6 months (C) Signup and view all the answers