40 Questions
What triggers the synthesis of chaperones and other quality control proteins?
Accumulation of unfolded proteins in the ER
What is the primary function of the Golgi apparatus in the secretory pathway?
Protein modification and sorting
What determines the size of the ER?
Demand for protein folding
Which of the following is NOT a function of the secretory pathway?
Protein synthesis
What is the primary function of the cis and trans regions of the Golgi apparatus?
Protein modification and sorting
What is the primary function of chaperone proteins in the ER?
To ensure proper protein folding and prevent misfolding
Which of the following is NOT a consequence of accumulation of misfolded proteins in the ER?
Stimulation of vesicle transport to the plasma membrane
What is the primary function of glycosylation in the ER?
To protect proteins from degradation and guide them to the proper organelle
Where do proteins undergo glycosylation in the secretory pathway?
In the ER lumen
What is the purpose of the unfolded protein response (UPR) in the ER?
To degrade misfolded proteins and maintain ER homeostasis
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
What happens to water-soluble proteins when they enter the ER?
They cross the ER membrane completely and are released into the lumen
What is the function of the ER in protein trafficking?
To modify and package proteins into vesicles
What is the fate of transmembrane proteins in the ER?
They only partially cross the ER and become embedded in the membrane
What is the common feature of all proteins synthesized by ribosomes in the nucleus?
They are all synthesized by a common pool of ribosomes
What is the role of the signal sequence in directing proteins to the ER?
To open the translocation channel
During protein synthesis, what happens to the signal sequence?
It is recognized by the SRP
What is the function of the SRP?
To recognize and bind to the signal sequence
What happens to proteins that are being synthesized and enter the ER?
They enter the lumen of the ER
What is the role of the signal sequence in transmembrane protein arrangement?
To determine the orientation of the protein in the lipid bilayer
What is the function of signal sequences in protein sorting?
To direct proteins to the correct compartment
What is the mechanism by which proteins enter the nucleus?
Through nuclear pores
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
Which of the following is a destination for proteins that enter the endoplasmic reticulum while being synthesized?
The ER lumen
What is the term for the process by which extracellular materials are captured by vesicles that bud inward from the plasma membrane?
Endocytosis
In which part of the Golgi apparatus does the additional glycosylation and sorting of proteins occur?
Trans face
What is the mechanism by which secretory proteins are released from the cell?
Exocytosis
What is the purpose of the constitutive exocytosis pathway in eukaryotic cells?
To operate continually in all eukaryotic cells
What is the environment of the trans-Golgi network that is essential for the formation of secretory vesicles?
Acidic pH and high calcium concentration
What is the process by which secretory vesicles release their contents in response to a signal?
Vesicle docking and fusion
Where do the bulk of proteins that enter peroxisomes come from?
The cytosol
What is the import signal for proteins entering peroxisomes?
SKL (ser-lys-leu)
What is a consequence of mutations that block peroxisomal protein import?
Zellweger syndrome
How do proteins enter peroxisomes from the cytosol?
Via protein translocators
What is the function of peroxisomal enzymes?
Breakdown of toxins, alcohols, and fatty acids
Do proteins need to unfold to enter peroxisomes?
No, protein translocators allow direct import
Which organelle is involved in protein synthesis and transport?
Endoplasmic reticulum
What is the function of protein receptors in protein transport?
To recognize and bind specific proteins
Which pathway is involved in the transport of proteins from the cytosol to peroxisomes?
Protein targeting pathway
What is the fate of individuals with Zellweger syndrome?
They usually do not survive beyond 6 months
Learn about the different types of modifications that occur to proteins in the Endoplasmic Reticulum, including disulfide bond formation and glycosylation. Understand how these modifications occur and their importance in protein function.
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