ER to Golgi Transport Quiz

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Questions and Answers

What is the primary function of the constitutive exocytosis pathway?

To remove waste products from the cell

To process incoming extracellular signals

To rapidly secrete hormones upon stimulation

To operate continuously, supplying lipids and proteins (correct)

In what circumstance does regulated exocytosis typically occur?

In response to a specific extracellular signal (correct)

As a means to transport materials into the cell

When there is an excess of cellular waste

Continuously, like the constitutive pathway

How do synaptic vesicles behave in an unstimulated neuron?

They release neurotransmitters spontaneously

They fuse with the plasma membrane immediately

They remain in the cytosol awaiting a signal (correct)

They dock with the plasma membrane continuously

What distinguishes regulated exocytosis from constitutive exocytosis?

Regulated exocytosis is triggered by signals, whereas constitutive occurs continuously Signup and view all the answers

What occurs during exocytosis?

Vesicles fuse with the plasma membrane to release contents. Signup and view all the answers

What is the primary function of the inner coat in vesicle transport?

To concentrate cargo Signup and view all the answers

What specific signal do resident ER proteins have for their retrieval?

KDEL signal Signup and view all the answers

What role does the KDEL receptor play in the retrieval pathway?

It recognizes the KDEL signal Signup and view all the answers

Which face of the Golgi apparatus is referred to as the 'cis face'?

The receiving side Signup and view all the answers

Why do some resident ER proteins end up being trapped in vesicles?

They are occasionally incorporated into vesicles Signup and view all the answers

What is indicated by a pH difference between cellular compartments?

The functional state of each compartment Signup and view all the answers

What main process occurs in the Golgi apparatus regarding proteins?

Proteins are modified and sorted Signup and view all the answers

What happens to COPI-coated vesicles after they bud off from the Golgi?

They recycle to the Golgi Signup and view all the answers

Which model of protein transport through the Golgi apparatus describes long-lived structures?

Vesicle transport model Signup and view all the answers

In the cisternal maturation model, how do Golgi cisternae change over time?

They mature by acquiring then losing specific Golgi-resident proteins. Signup and view all the answers

What is the primary method of transport for cargo proteins in the vesicle transport model?

Transport vesicles Signup and view all the answers

Which of the following is NOT characteristic of the vesicle transport model?

Cisternae are dynamic structures Signup and view all the answers

Which statement about the Golgi apparatus is false?

Golgi cisternae are static in function. Signup and view all the answers

Which model of protein transport is suggested to be the most correct?

Cisternal maturation model is more likely correct Signup and view all the answers

How do the vesicle transport and cisternal maturation models differ fundamentally?

In their depiction of the dynamics of Golgi cisternae. Signup and view all the answers

What role do Golgi-resident proteins play in the vesicle transport model?

They help maintain the identity of the cisternae. Signup and view all the answers

What mechanism is used primarily for delivering proteins from the ER to the Golgi?

Transport vesicles Signup and view all the answers

What is a key function of the inner coat of a vesicle during transport?

Concentration of cargo Signup and view all the answers

What do exit signals commonly consist of for proteins destined for the Golgi?

Amino acid sequences Signup and view all the answers

How does the outer coat of a vesicle contribute to its formation?

By shaping and deforming the membrane Signup and view all the answers

What triggers the unfolded protein response (UPR) in the ER?

Accumulation of misfolded proteins Signup and view all the answers

What happens to soluble cargo once the vesicle fuses with the Golgi?

It is released from the cargo receptor Signup and view all the answers

Which of the following statements about transport mechanisms to the Golgi is true?

Both soluble and membrane-bound proteins utilize exit signals Signup and view all the answers

What is a primary role of the ER in the endomembrane system?

Protein folding and quality control Signup and view all the answers

What aspect differentiates COPII vesicles in the context of vesicular transport?

They are used for ER to Golgi vesicle traffic Signup and view all the answers

What is the main consequence of an unfolded protein response (UPR)?

Triggering of apoptosis pathways Signup and view all the answers

Which mechanism is primarily responsible for delivering proteins from the ER to the Golgi?

Delivery by transport vesicles Signup and view all the answers

What is the role of the COPII vesicles in vesicle transport?

They are involved in ER to Golgi traffic Signup and view all the answers

What is the primary function of the outer coat of a transport vesicle?

To shape the vesicle and deform the membrane Signup and view all the answers

Which statement best describes the exit signals for proteins destined for the Golgi?

They are often an amino acid sequence on the protein Signup and view all the answers

What is the outcome of the unfolded protein response (UPR) triggered by misfolded proteins in the ER?

Activation of chaperone proteins Signup and view all the answers

Which of the following best describes the functions of the inner coat of a vesicle?

To concentrate cargo proteins Signup and view all the answers

How are membrane-bound proteins with exit signals typically processed?

They serve as cargo receptors and recycle back to the ER Signup and view all the answers

What occurs to soluble cargo once the transport vesicle fuses with the Golgi membrane?

It is released by the cargo receptor Signup and view all the answers

What determines the specific protein movements within the endomembrane system?

Exit signals and transport mechanisms Signup and view all the answers

What initiates the formation of vesicles in the process of ER to Golgi transport?

Concentration of cargo due to the inner coat Signup and view all the answers

What is a primary characteristic of the constitutive exocytosis pathway?

It operates continuously in all cells. Signup and view all the answers

Which statement accurately describes the regulated exocytosis pathway?

It responds to specific extracellular signals for secretion. Signup and view all the answers

What triggers the fusion of synaptic vesicles with the plasma membrane in stimulated neurons?

Membrane depolarization. Signup and view all the answers

What is the role of the secretory pathway in cellular processes?

It supplies newly synthesized proteins and lipids to the plasma membrane. Signup and view all the answers

Which of the following best describes the behavior of vesicles in an unstimulated nerve terminal?

Vesicles remain in the cytosol awaiting a signal. Signup and view all the answers

What primarily differentiates the constitutive and regulated exocytosis pathways?

The source of the triggering signal for secretion. Signup and view all the answers

How does exocytosis contribute to neurotransmitter function?

By secreting neurotransmitters into the synaptic cleft. Signup and view all the answers

What typically occurs within a cell during the regulated exocytosis pathway?

Rapid secretion of hormones or enzymes following stimulation. Signup and view all the answers

During exocytosis, what is the fate of the vesicle once it fuses with the plasma membrane?

It releases its contents into the extracellular space. Signup and view all the answers

What characterizes the vesicle transport model of protein transport through the Golgi apparatus?

Golgi-resident proteins are delivered by transport vesicles. Signup and view all the answers

Which of the following statements accurately describes the cisternal maturation model?

Cisternae mature by acquiring and losing Golgi-resident proteins. Signup and view all the answers

What is a key difference between the vesicle transport model and the cisternal maturation model?

The vesicle transport model has static structures retaining proteins. Signup and view all the answers

Which aspect of Golgi cisternae is highlighted in the vesicle transport model?

Cisternae are immutable, retaining their proteins permanently. Signup and view all the answers

How do cargo proteins typically move from one cisterna to another in the vesicle transport model?

By being packaged into transport vesicles. Signup and view all the answers

Which point supports the concept of cisternal maturation as a correct model of protein transport?

The maturation process allows for progressive alteration of proteins. Signup and view all the answers

What is implied by the statement that Golgi cisternae are 'long-lived structures' in the vesicle transport model?

Cisternae maintain a consistent repertoire of resident proteins. Signup and view all the answers

What is the primary characteristic of Golgi cisternae in the context of the vesicle transport model?

They are stable, unchanging reservoirs for resident proteins. Signup and view all the answers

What occurs during the transit of proteins through the Golgi apparatus according to the cisternal maturation model?

Cisternae progress through stages, acquiring and losing factors. Signup and view all the answers

Which model is suggested to be the most accurate depiction of protein transport through the Golgi apparatus?

The cisternal maturation model is suggested as the most likely correct model. Signup and view all the answers

What function does the outer coat of the vesicle serve during transport?

It shapes the vesicle by deforming the membrane. Signup and view all the answers

What occurs to escaped resident ER proteins during their transport?

They are returned to the ER via COPI-coated vesicles. Signup and view all the answers

Which pH environment is indicated by decreasing pH from Golgi to ER?

The Golgi has a more alkaline environment than the ER. Signup and view all the answers

What modification is NOT necessary for protein trafficking through the Golgi?

Protein degradation signals. Signup and view all the answers

Which pathway does the KDEL signal primarily facilitate?

Retrieval of ER resident proteins from the Golgi. Signup and view all the answers

What is the role of the Golgi apparatus in the endomembrane system?

It functions to modify, sort, and package proteins. Signup and view all the answers

What describes the structure of the Golgi apparatus?

A series of flattened membrane-enclosed compartments. Signup and view all the answers

Which of the following statements correctly describes the COPI-mediated retrieval pathway?

It recycles receptors along with resident proteins back to the ER. Signup and view all the answers

What characteristic is typical of the retrieval pathway in cellular transport mechanisms?

It allows the return of escaped proteins to their origin. Signup and view all the answers

What is a critical factor influencing the selection of cargo for vesicle transport?

The presence of specific retrieval signals on the cargo. Signup and view all the answers

Study Notes

ER to Golgi Transport

ER is the gateway to the endomembrane system
ER to Golgi transport uses COPII vesicles
Exit signals on proteins are commonly an amino acid sequence
Both soluble and membrane-bound cargo proteins can have exit signals
Membrane-bound proteins with exit signals can be destined for another organelle in the endomembrane system or can act as cargo receptors for soluble proteins
The coat of vesicles serves two main functions:
- The inner coat concentrates cargo
- The outer coat shapes the vesicle
Exit from the ER is controlled to ensure protein quality control
Accumulation of misfolded proteins in the ER triggers an unfolded protein response (UPR)
Vesicles from the ER uncoat and fuse with the Golgi
Cargo receptors release soluble cargo following fusion with the target membrane
The pH difference between organelles is important for regulating the binding of cargo receptors and soluble cargo.
Occasionally resident ER proteins get trapped in vesicles
Escaped resident ER proteins are returned to the ER through a retrieval pathway
Resident ER proteins have an ER retrieval signal
KDEL is a common ER retrieval signal
The KDEL receptor in the Golgi recognizes the ER retrieval signal
The KDEL receptor with its bound resident ER protein is incorporated into COPI coated vesicles
COPI vesicles bud off the Golgi and fuse with the ER

Golgi

The Golgi apparatus is a series of cisternae, flattened membrane-enclosed compartments
Proteins are modified in the Golgi apparatus
There are two main models for protein transport through the Golgi:
- Vesicle transport model, which states that Golgi cisternae are long-lived structures and cargo proteins are transported by vesicles
- Cisternal Maturation model, which states that Golgi cisternae are dynamic structures and mature from early to late by acquiring and then losing specific Golgi-resident proteins
The cisternal maturation model is most likely the correct model
The Golgi is the next step in the secretory pathway to the plasma membrane.

Exocytosis

Exocytosis is the excretion of material from the cell by vesicle fusion with the plasma membrane
Exocytosis can be either constitutive or regulated
Constitutive exocytosis is essential for all cells and constantly supplies newly made proteins and lipids to the plasma membrane
Regulated exocytosis is mainly found in specialized cells that secrete products rapidly on demand (hormones, digestive enzymes, neurotransmitters)

Neurotransmitter Release

In an unstimulated nerve terminal, vesicles are in the cytosol
In a stimulated nerve terminal, a signal stimulates the fusion of synaptic vesicles with the plasma membrane, causing the release of neurotransmitters into the synaptic cleft

ER to Golgi transport

Proteins are transported from the ER to the Golgi via transport vesicles, which are coated with COPII proteins.
Proteins that are destined for the Golgi have an exit signal sequence, typically an amino acid sequence.
The coat of COPII vesicles serves to concentrate cargo and deform the membrane.
The ER also has quality control mechanisms to prevent misfolded proteins from entering the Golgi.
The unfolded protein response (UPR) is triggered by an accumulation of misfolded proteins in the ER.
The UPR involves signaling pathways that can lead to increased protein folding capacity or cell death.
Once a COPII vesicle reaches the Golgi, it uncoats and fuses with the Golgi membrane.
Cargo receptors release their cargo in the Golgi.
The pH difference between the ER and the Golgi plays a role in the release of cargo from cargo receptors.

Golgi

The Golgi apparatus is a series of flattened membrane-enclosed compartments called cisternae.
The cis face of the Golgi is closer to the ER and the trans face is further away.
Different proteins are modified in the Golgi compartments, often with the assistance of enzymes.
Cargo proteins are transported through the Golgi by two potential mechanisms: the vesicle transport model and the cisternal maturation model.
The cisternal maturation model is currently considered the most likely model for protein transport through the Golgi.

Exocytosis

Exocytosis is the process of releasing material from the cell by vesicle fusion with the plasma membrane.
There are two types of exocytosis: constitutive exocytosis and regulated exocytosis.
Constitutive exocytosis occurs continuously and is essential for the delivery of lipids and proteins to the plasma membrane and the secretion of proteins to the extracellular space.
Regulated exocytosis occurs in response to an extracellular signal, such as a hormone or neurotransmitter, and is common in cells specialized for secreting products.
The release of neurotransmitters from neurons is an example of regulated exocytosis.
In a stimulated neuron, synaptic vesicles fuse with the plasma membrane causing the release of neurotransmitters into the synaptic cleft.
During endocytosis, the plasma membrane invaginates and pinches off to form vesicles that carry material into the cell.

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Description

Test your understanding of how proteins are transported from the endoplasmic reticulum (ER) to the Golgi apparatus. This quiz covers topics such as vesicle formation, cargo concentration, and the role of pH in cargo binding. Challenge yourself with questions about the mechanisms that ensure protein quality control within the endomembrane system.