Podcast
Questions and Answers
What is the primary function of the constitutive exocytosis pathway?
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 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?
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?
What distinguishes regulated exocytosis from constitutive exocytosis?
What occurs during exocytosis?
What occurs during exocytosis?
What is the primary function of the inner coat in vesicle transport?
What is the primary function of the inner coat in vesicle transport?
What specific signal do resident ER proteins have for their retrieval?
What specific signal do resident ER proteins have for their retrieval?
What role does the KDEL receptor play in the retrieval pathway?
What role does the KDEL receptor play in the retrieval pathway?
Which face of the Golgi apparatus is referred to as the 'cis face'?
Which face of the Golgi apparatus is referred to as the 'cis face'?
Why do some resident ER proteins end up being trapped in vesicles?
Why do some resident ER proteins end up being trapped in vesicles?
What is indicated by a pH difference between cellular compartments?
What is indicated by a pH difference between cellular compartments?
What main process occurs in the Golgi apparatus regarding proteins?
What main process occurs in the Golgi apparatus regarding proteins?
What happens to COPI-coated vesicles after they bud off from the Golgi?
What happens to COPI-coated vesicles after they bud off from the Golgi?
Which model of protein transport through the Golgi apparatus describes long-lived structures?
Which model of protein transport through the Golgi apparatus describes long-lived structures?
In the cisternal maturation model, how do Golgi cisternae change over time?
In the cisternal maturation model, how do Golgi cisternae change over time?
What is the primary method of transport for cargo proteins in the vesicle transport model?
What is the primary method of transport for cargo proteins in the vesicle transport model?
Which of the following is NOT characteristic of the vesicle transport model?
Which of the following is NOT characteristic of the vesicle transport model?
Which statement about the Golgi apparatus is false?
Which statement about the Golgi apparatus is false?
Which model of protein transport is suggested to be the most correct?
Which model of protein transport is suggested to be the most correct?
How do the vesicle transport and cisternal maturation models differ fundamentally?
How do the vesicle transport and cisternal maturation models differ fundamentally?
What role do Golgi-resident proteins play in the vesicle transport model?
What role do Golgi-resident proteins play in the vesicle transport model?
What mechanism is used primarily for delivering proteins from the ER to the Golgi?
What mechanism is used primarily for delivering proteins from the ER to the Golgi?
What is a key function of the inner coat of a vesicle during transport?
What is a key function of the inner coat of a vesicle during transport?
What do exit signals commonly consist of for proteins destined for the Golgi?
What do exit signals commonly consist of for proteins destined for the Golgi?
How does the outer coat of a vesicle contribute to its formation?
How does the outer coat of a vesicle contribute to its formation?
What triggers the unfolded protein response (UPR) in the ER?
What triggers the unfolded protein response (UPR) in the ER?
What happens to soluble cargo once the vesicle fuses with the Golgi?
What happens to soluble cargo once the vesicle fuses with the Golgi?
Which of the following statements about transport mechanisms to the Golgi is true?
Which of the following statements about transport mechanisms to the Golgi is true?
What is a primary role of the ER in the endomembrane system?
What is a primary role of the ER in the endomembrane system?
What aspect differentiates COPII vesicles in the context of vesicular transport?
What aspect differentiates COPII vesicles in the context of vesicular transport?
What is the main consequence of an unfolded protein response (UPR)?
What is the main consequence of an unfolded protein response (UPR)?
Which mechanism is primarily responsible for delivering proteins from the ER to the Golgi?
Which mechanism is primarily responsible for delivering proteins from the ER to the Golgi?
What is the role of the COPII vesicles in vesicle transport?
What is the role of the COPII vesicles in vesicle transport?
What is the primary function of the outer coat of a transport vesicle?
What is the primary function of the outer coat of a transport vesicle?
Which statement best describes the exit signals for proteins destined for the Golgi?
Which statement best describes the exit signals for proteins destined for the Golgi?
What is the outcome of the unfolded protein response (UPR) triggered by misfolded proteins in the ER?
What is the outcome of the unfolded protein response (UPR) triggered by misfolded proteins in the ER?
Which of the following best describes the functions of the inner coat of a vesicle?
Which of the following best describes the functions of the inner coat of a vesicle?
How are membrane-bound proteins with exit signals typically processed?
How are membrane-bound proteins with exit signals typically processed?
What occurs to soluble cargo once the transport vesicle fuses with the Golgi membrane?
What occurs to soluble cargo once the transport vesicle fuses with the Golgi membrane?
What determines the specific protein movements within the endomembrane system?
What determines the specific protein movements within the endomembrane system?
What initiates the formation of vesicles in the process of ER to Golgi transport?
What initiates the formation of vesicles in the process of ER to Golgi transport?
What is a primary characteristic of the constitutive exocytosis pathway?
What is a primary characteristic of the constitutive exocytosis pathway?
Which statement accurately describes the regulated exocytosis pathway?
Which statement accurately describes the regulated exocytosis pathway?
What triggers the fusion of synaptic vesicles with the plasma membrane in stimulated neurons?
What triggers the fusion of synaptic vesicles with the plasma membrane in stimulated neurons?
What is the role of the secretory pathway in cellular processes?
What is the role of the secretory pathway in cellular processes?
Which of the following best describes the behavior of vesicles in an unstimulated nerve terminal?
Which of the following best describes the behavior of vesicles in an unstimulated nerve terminal?
What primarily differentiates the constitutive and regulated exocytosis pathways?
What primarily differentiates the constitutive and regulated exocytosis pathways?
How does exocytosis contribute to neurotransmitter function?
How does exocytosis contribute to neurotransmitter function?
What typically occurs within a cell during the regulated exocytosis pathway?
What typically occurs within a cell during the regulated exocytosis pathway?
During exocytosis, what is the fate of the vesicle once it fuses with the plasma membrane?
During exocytosis, what is the fate of the vesicle once it fuses with the plasma membrane?
What characterizes the vesicle transport model of protein transport through the Golgi apparatus?
What characterizes the vesicle transport model of protein transport through the Golgi apparatus?
Which of the following statements accurately describes the cisternal maturation model?
Which of the following statements accurately describes the cisternal maturation model?
What is a key difference between the vesicle transport model and the cisternal maturation model?
What is a key difference between the vesicle transport model and the cisternal maturation model?
Which aspect of Golgi cisternae is highlighted in the vesicle transport model?
Which aspect of Golgi cisternae is highlighted in the vesicle transport model?
How do cargo proteins typically move from one cisterna to another in the vesicle transport model?
How do cargo proteins typically move from one cisterna to another in the vesicle transport model?
Which point supports the concept of cisternal maturation as a correct model of protein transport?
Which point supports the concept of cisternal maturation as a correct model of protein transport?
What is implied by the statement that Golgi cisternae are 'long-lived structures' in the vesicle transport model?
What is implied by the statement that Golgi cisternae are 'long-lived structures' in the vesicle transport model?
What is the primary characteristic of Golgi cisternae in the context of the vesicle transport model?
What is the primary characteristic of Golgi cisternae in the context of the vesicle transport model?
What occurs during the transit of proteins through the Golgi apparatus according to the cisternal maturation model?
What occurs during the transit of proteins through the Golgi apparatus according to the cisternal maturation model?
Which model is suggested to be the most accurate depiction of protein transport through the Golgi apparatus?
Which model is suggested to be the most accurate depiction of protein transport through the Golgi apparatus?
What function does the outer coat of the vesicle serve during transport?
What function does the outer coat of the vesicle serve during transport?
What occurs to escaped resident ER proteins during their transport?
What occurs to escaped resident ER proteins during their transport?
Which pH environment is indicated by decreasing pH from Golgi to ER?
Which pH environment is indicated by decreasing pH from Golgi to ER?
What modification is NOT necessary for protein trafficking through the Golgi?
What modification is NOT necessary for protein trafficking through the Golgi?
Which pathway does the KDEL signal primarily facilitate?
Which pathway does the KDEL signal primarily facilitate?
What is the role of the Golgi apparatus in the endomembrane system?
What is the role of the Golgi apparatus in the endomembrane system?
What describes the structure of the Golgi apparatus?
What describes the structure of the Golgi apparatus?
Which of the following statements correctly describes the COPI-mediated retrieval pathway?
Which of the following statements correctly describes the COPI-mediated retrieval pathway?
What characteristic is typical of the retrieval pathway in cellular transport mechanisms?
What characteristic is typical of the retrieval pathway in cellular transport mechanisms?
What is a critical factor influencing the selection of cargo for vesicle transport?
What is a critical factor influencing the selection of cargo for vesicle transport?
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.
