Cell Biology: Intracellular Transport

Questions and Answers

Which process describes the movement of proteins from the ER to the extracellular space?

Autophagy pathway

Retrieval pathway

Endocytic pathway

Biosynthetic-secretory pathway (correct)

Which of the following pathways involves the transport of materials from the extracellular space to the lysosome?

Retrieval pathway

Biosynthetic-secretory pathway

Autophagy pathway

Endocytic pathway (correct)

What is the main purpose of molecular chaperones in the ER?

Form vesicles for exocytosis

Transport proteins to the Golgi apparatus

Modify proteins by glycosylation

Assist in the proper folding of proteins (correct)

Which of the following correctly sequences the steps of the exocytosis process?

Vesicle formation, Golgi processing, membrane fusion, secretion Signup and view all the answers

What is the role of glycosylation in the ER?

Adding carbohydrate groups to proteins Signup and view all the answers

How does the retrieval pathway function in vesicular transport?

Returns escaped proteins from the Golgi back to the ER Signup and view all the answers

What structural change occurs to vesicles during their formation?

They bud off from the membrane as coated vesicles Signup and view all the answers

Which of these statements about autophagy is correct?

It is a pathway for recycling cellular components. Signup and view all the answers

What is the primary function of the CFTR protein in epithelial cells?

Functions as a Cl- channel Signup and view all the answers

The CFTRΔF508 mutation causes what specific issue with the CFTR protein?

Improper folding and degradation in the ER Signup and view all the answers

What characteristic enables vesicle transport to facilitate protein trafficking?

Vesicles can fuse with different membrane-enclosed compartments Signup and view all the answers

Which of the following processes is likely triggered by the accumulation of misfolded proteins in the ER?

Unfolded protein response Signup and view all the answers

The vesicle transport mechanism is crucial because it prevents what potential problem in protein trafficking?

Disruption of protein homeostasis Signup and view all the answers

How does ER quality control contribute to cellular health?

By ensuring only correctly folded proteins proceed Signup and view all the answers

Glycosylation is important because it primarily plays a role in what aspect of protein functionality?

Determining the stability and trafficking of proteins Signup and view all the answers

What happens to a significant percentage of polypeptides synthesized in the ER?

They fail to reach their final destinations due to misfolding Signup and view all the answers

What is the primary role of the coat on vesicles during transport?

To help select appropriate cargoes for transport Signup and view all the answers

Which type of vesicle is responsible for transporting cargo from the Golgi to the endosome?

Clathrin-coated vesicles Signup and view all the answers

Which vesicle type is involved in transporting proteins from the ER back to the Golgi?

COPI-coated vesicles Signup and view all the answers

From which cellular location do COPII-coated vesicles primarily transport substances?

From the ER to the Golgi Signup and view all the answers

What is the source of the cargo for retromer-coated vesicles?

From endosome back to Golgi Signup and view all the answers

Which statement accurately characterizes COPI-coated vesicles?

They are involved in retrograde transport from the Golgi back to the ER Signup and view all the answers

What is a key function of clathrin-coated vesicles?

Transporting cargo from the plasma membrane to the early endosome Signup and view all the answers

Which vesicular transport process is responsible for the movement of proteins synthesized in the ER to the Golgi apparatus?

COPII-mediated transport Signup and view all the answers

What does the retrograde transport mechanism primarily facilitate?

The return of proteins from the Golgi to the ER Signup and view all the answers

Study Notes

Intracellular Protein Trafficking Pathways

Biosynthetic-secretory pathway involves transport from Endoplasmic Reticulum (ER) to Golgi, then to extracellular space or endosome, and ultimately to lysosome.
Retrieval pathway allows for recycling of proteins back to the ER or Golgi from endosomes.
Endocytic pathway facilitates the movement of substances from extracellular space to endosomes and subsequently to lysosomes.
Autophagy pathway involves the degradation of cytoplasmic components.

Key Steps in Vesicle Transport

Transport vesicles form at specialized membrane regions, detached as coated vesicles.
Vesicle transport allows exchange of contents between distinct membrane-enclosed compartments without direct membrane crossing.

Cystic Fibrosis Overview

Cystic fibrosis is an autosomal recessive disorder resulting from mutations in the CFTR gene.
The CFTR gene encodes a multi-spanning 1480 amino acid membrane protein that functions as a chloride channel in exocrine epithelial cells.
CFTR is present in the apical membranes of various organs, including lungs, pancreas, and intestines.

Mutation Effects on CFTR

CFTRΔF508 mutation leads to misfolding of the protein, preventing its transport to the plasma membrane and resulting in degradation within the ER.
Quality control mechanisms in the ER ensure misfolded proteins do not interfere with normal protein function, causing a significant number of newly synthesized proteins to not reach their destinations.
Accumulation of misfolded proteins can lead to an unfolded protein response (UPR), ER-associated degradation, and apoptosis.

Vesicle Transport Mechanisms

Clathrin-coated vesicles transport from Golgi to endosomes and from plasma membrane to early endosomes.
COPI-coated vesicles mediate retrograde transport from Golgi back to ER.
COPII-coated vesicles facilitate anterograde transport from ER to Golgi.
Retromer-coated vesicles transport from endosomes back to Golgi.
Coats of vesicles select appropriate cargo molecules for transport, ensuring correct delivery across compartments.

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Description

This quiz covers the lumens and membranes of intracellular organelles such as the endoplasmic reticulum, Golgi apparatus, endosome, and lysosome. It also explores the biosynthetic-secretory pathways and vesicle transport mechanisms involved in protein trafficking. Test your knowledge of cell biology!