Podcast
Questions and Answers
Cholesterol acts to reduce permeability of the cell ______.
Cholesterol acts to reduce permeability of the cell ______.
membrane
The Smooth ER is involved in calcium ______ and drug detoxification.
The Smooth ER is involved in calcium ______ and drug detoxification.
storage
Ribosomal sub-units complex together with mRNA in the cytoplasm to initiate ______ synthesis.
Ribosomal sub-units complex together with mRNA in the cytoplasm to initiate ______ synthesis.
protein
The signal recognition particle (SRP) recognizes and binds to the signal ______.
The signal recognition particle (SRP) recognizes and binds to the signal ______.
Protein distribution to the ER begins with signal ______ particle recognition.
Protein distribution to the ER begins with signal ______ particle recognition.
The carboxy or amino ______ can be located in the cytosol.
The carboxy or amino ______ can be located in the cytosol.
ER is a major ______ folding site.
ER is a major ______ folding site.
BiP chaperone protein is responsible for mediating protein ______.
BiP chaperone protein is responsible for mediating protein ______.
Protein disulfide isomerase catalyzes the oxidation of ______ groups to form disulfide bonds.
Protein disulfide isomerase catalyzes the oxidation of ______ groups to form disulfide bonds.
About half of the proteins processed in ER are ______.
About half of the proteins processed in ER are ______.
N-linked glycosylation stabilises proteins by masking ______, proteolytic cleavage sites or immune recognition.
N-linked glycosylation stabilises proteins by masking ______, proteolytic cleavage sites or immune recognition.
An unfolded protein will undergo continuous cycles of glucose ______ and glucose addition until it has achieved its fully folded state.
An unfolded protein will undergo continuous cycles of glucose ______ and glucose addition until it has achieved its fully folded state.
The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the ______.
The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the ______.
Once 3 glucose and 1 mannose are ______, the protein can be transported to the Golgi.
Once 3 glucose and 1 mannose are ______, the protein can be transported to the Golgi.
The accumulation of unfolded, misfolded or damaged proteins leads to ER ______.
The accumulation of unfolded, misfolded or damaged proteins leads to ER ______.
The endoplasmic reticulum (ER) is a labyrinth of branching tubules and sacs that is continuous with the outer nuclear ______.
The endoplasmic reticulum (ER) is a labyrinth of branching tubules and sacs that is continuous with the outer nuclear ______.
When the misfolded proteins exceed ER degradation capacity, the unfolded protein ______ is activated.
When the misfolded proteins exceed ER degradation capacity, the unfolded protein ______ is activated.
The rough ER is characterized by flattened sheets with ______ bound to its cytosolic surface.
The rough ER is characterized by flattened sheets with ______ bound to its cytosolic surface.
Smooth ER is involved in lipid biosynthesis, carbohydrate metabolism, calcium storage, and ______ of drugs and poisons.
Smooth ER is involved in lipid biosynthesis, carbohydrate metabolism, calcium storage, and ______ of drugs and poisons.
The internal space of the endoplasmic reticulum is called the ______.
The internal space of the endoplasmic reticulum is called the ______.
The primary function of the rough ER is protein ______.
The primary function of the rough ER is protein ______.
Each step in lipid synthesis in the smooth ER is catalyzed by ______ within the organelle.
Each step in lipid synthesis in the smooth ER is catalyzed by ______ within the organelle.
Rough ER also contributes to protein folding and ______ of incorrect proteins.
Rough ER also contributes to protein folding and ______ of incorrect proteins.
The SRP-ribosome complex binds to the SRP ______ and the translocation complex on ER membrane.
The SRP-ribosome complex binds to the SRP ______ and the translocation complex on ER membrane.
During protein synthesis, the signal sequence enters the ______ in the ER membrane.
During protein synthesis, the signal sequence enters the ______ in the ER membrane.
For secretory proteins, the protein is completely translocated across the ______.
For secretory proteins, the protein is completely translocated across the ______.
The amino acid signal sequence is cleaved by a signal ______.
The amino acid signal sequence is cleaved by a signal ______.
Transmembrane proteins can have a second hydrophobic region known as a ‘Stop Transfer ______.
Transmembrane proteins can have a second hydrophobic region known as a ‘Stop Transfer ______.
Types II and III transmembrane proteins have an internal amino acid signal ______.
Types II and III transmembrane proteins have an internal amino acid signal ______.
In multipass transmembrane proteins, there are alternating internal signal sequences and Stop ______ signals.
In multipass transmembrane proteins, there are alternating internal signal sequences and Stop ______ signals.
Examples of transmembrane proteins include receptor tyrosine kinases, integrins, or cytokine ______.
Examples of transmembrane proteins include receptor tyrosine kinases, integrins, or cytokine ______.
The rough ER is primarily responsible for protein ______.
The rough ER is primarily responsible for protein ______.
The smooth ER performs diverse metabolic functions, including lipid ______.
The smooth ER performs diverse metabolic functions, including lipid ______.
Endocytosis is the ______ of nutrients or removal of plasma membrane components.
Endocytosis is the ______ of nutrients or removal of plasma membrane components.
COPII-coated vesicles are involved in transportation from the ER to the ______.
COPII-coated vesicles are involved in transportation from the ER to the ______.
The Golgi apparatus consists of multiple discrete compartments called ______.
The Golgi apparatus consists of multiple discrete compartments called ______.
The trans Golgi network acts as a ______ center for sorting and distribution.
The trans Golgi network acts as a ______ center for sorting and distribution.
N-linked glycosylation is a signaling molecule in the ______ process.
N-linked glycosylation is a signaling molecule in the ______ process.
Transport vesicles are membrane-enclosed ______ to move cargo between compartments.
Transport vesicles are membrane-enclosed ______ to move cargo between compartments.
The movement of cargo from the cis Golgi network to the ______ Golgi network is an essential step in processing.
The movement of cargo from the cis Golgi network to the ______ Golgi network is an essential step in processing.
Chaperone proteins in the ER lumen mediate protein ______.
Chaperone proteins in the ER lumen mediate protein ______.
The Smooth ER has tubular structure with no _____.
The Smooth ER has tubular structure with no _____.
Protein biosynthesis in the Rough ER involves water soluble secretory proteins and ______ proteins.
Protein biosynthesis in the Rough ER involves water soluble secretory proteins and ______ proteins.
Water soluble proteins in the RER are ______ across the ER membrane.
Water soluble proteins in the RER are ______ across the ER membrane.
Transmembrane proteins in the RER are _____ within the ER membrane.
Transmembrane proteins in the RER are _____ within the ER membrane.
Cholesterol is involved in _____ synthesis and steroid synthesis.
Cholesterol is involved in _____ synthesis and steroid synthesis.
Membranes largely consist of phospholipids, ______ and cholesterol.
Membranes largely consist of phospholipids, ______ and cholesterol.
Ubiquitin-proteosome system: translocated into the cytosol, tagged with ubiquitin, and degraded by ______.
Ubiquitin-proteosome system: translocated into the cytosol, tagged with ubiquitin, and degraded by ______.
Autophagic-lysosomal system: aberrant protein fragments degraded by ______.
Autophagic-lysosomal system: aberrant protein fragments degraded by ______.
Cholesterol plays a role in membrane structure and acts to reduce ______ of the cell membrane.
Cholesterol plays a role in membrane structure and acts to reduce ______ of the cell membrane.
The Smooth ER is a site for drug ______, aiding in the detoxification of harmful substances.
The Smooth ER is a site for drug ______, aiding in the detoxification of harmful substances.
Translation always begins in the ______, except for a few proteins made in certain organelles.
Translation always begins in the ______, except for a few proteins made in certain organelles.
Calcium is stored in the ER lumen, where it binds to specific ______ proteins.
Calcium is stored in the ER lumen, where it binds to specific ______ proteins.
The primary function of the rough ER is protein ______, particularly for secretory proteins.
The primary function of the rough ER is protein ______, particularly for secretory proteins.
N-linked glycosylation stabilises proteins by masking ______ stretches.
N-linked glycosylation stabilises proteins by masking ______ stretches.
Once 3 glucose and 1 mannose are trimmed, the protein can be transported to the ______.
Once 3 glucose and 1 mannose are trimmed, the protein can be transported to the ______.
Chaperone proteins recognise and bind to ______ molecules.
Chaperone proteins recognise and bind to ______ molecules.
The _____ apparatus is part of the endomembrane system and plays a key role in modifying proteins.
The _____ apparatus is part of the endomembrane system and plays a key role in modifying proteins.
The rough endoplasmic reticulum (RER) is characterized by flattened sheets with _____ on its cytosolic surface.
The rough endoplasmic reticulum (RER) is characterized by flattened sheets with _____ on its cytosolic surface.
The internal space of the endoplasmic reticulum is referred to as the _____ lumen.
The internal space of the endoplasmic reticulum is referred to as the _____ lumen.
The endoplasmic reticulum (ER) constitutes more than _____ of the total membrane of an average animal cell.
The endoplasmic reticulum (ER) constitutes more than _____ of the total membrane of an average animal cell.
The _____ endoplasmic reticulum (SER) has a tubular structure and is involved in various metabolic functions.
The _____ endoplasmic reticulum (SER) has a tubular structure and is involved in various metabolic functions.
Each step in lipid synthesis is catalyzed by _____ within the smooth ER.
Each step in lipid synthesis is catalyzed by _____ within the smooth ER.
The transmembrane protein moves along the membrane ______ using the signal sequence.
The transmembrane protein moves along the membrane ______ using the signal sequence.
The signal sequence enters the ______ in the ER membrane during protein synthesis.
The signal sequence enters the ______ in the ER membrane during protein synthesis.
Molecular chaperones and folding enzymes in the ER __________ assist in folding and control subsequent release from the ER.
Molecular chaperones and folding enzymes in the ER __________ assist in folding and control subsequent release from the ER.
BiP is an ATP-driven protein that mediates protein __________ and prevents protein aggregation.
BiP is an ATP-driven protein that mediates protein __________ and prevents protein aggregation.
N-linked glycosylation involves the addition of a pre-formed precursor __________ onto the side chain of asparagine.
N-linked glycosylation involves the addition of a pre-formed precursor __________ onto the side chain of asparagine.
Protein disulfide isomerase catalyzes the oxidation of sulfhydryl groups on cysteines to form __________ bonds.
Protein disulfide isomerase catalyzes the oxidation of sulfhydryl groups on cysteines to form __________ bonds.
About half of the proteins processed in the ER are __________.
About half of the proteins processed in the ER are __________.
The rough ER is primarily responsible for ______ biosynthesis.
The rough ER is primarily responsible for ______ biosynthesis.
Smooth ER is involved in lipid ______ and drug detoxification.
Smooth ER is involved in lipid ______ and drug detoxification.
The ______ Golgi network acts as a sorting center for distribution.
The ______ Golgi network acts as a sorting center for distribution.
N-linked glycosylation is a signaling molecule in the folding ______.
N-linked glycosylation is a signaling molecule in the folding ______.
Vesicular tubular clusters move along ______ towards the Golgi apparatus.
Vesicular tubular clusters move along ______ towards the Golgi apparatus.
What is the primary function of the Smooth ER?
What is the primary function of the Smooth ER?
Which statement correctly describes the role of ribosomal sub-units during protein biosynthesis?
Which statement correctly describes the role of ribosomal sub-units during protein biosynthesis?
What role does cholesterol play in cellular membranes?
What role does cholesterol play in cellular membranes?
What is the function of the signal recognition particle (SRP)?
What is the function of the signal recognition particle (SRP)?
What process is enhanced by the presence of cyclic enzymes like cytochrome P450 in the Smooth ER?
What process is enhanced by the presence of cyclic enzymes like cytochrome P450 in the Smooth ER?
What role does BiP chaperone protein primarily serve in the endoplasmic reticulum (ER)?
What role does BiP chaperone protein primarily serve in the endoplasmic reticulum (ER)?
Which of the following statements about protein disulfide isomerase is true?
Which of the following statements about protein disulfide isomerase is true?
What percentage of glycoproteins undergo N-linked glycosylation in the ER lumen?
What percentage of glycoproteins undergo N-linked glycosylation in the ER lumen?
What is a primary role of N-linked glycosylation in proteins?
What is a primary role of N-linked glycosylation in proteins?
What is the primary function of molecular chaperones in the ER?
What is the primary function of molecular chaperones in the ER?
What happens to an unfolded protein undergoing quality control in the endoplasmic reticulum?
What happens to an unfolded protein undergoing quality control in the endoplasmic reticulum?
Which feature of ER resident proteins is crucial for their retention in the ER lumen?
Which feature of ER resident proteins is crucial for their retention in the ER lumen?
What consequence occurs when misfolded proteins accumulate in the endoplasmic reticulum?
What consequence occurs when misfolded proteins accumulate in the endoplasmic reticulum?
What is the fate of proteins that do not achieve their fully folded state in the endoplasmic reticulum?
What is the fate of proteins that do not achieve their fully folded state in the endoplasmic reticulum?
How does the endoplasmic reticulum quality control (ERQC) system ensure the integrity of glycoproteins?
How does the endoplasmic reticulum quality control (ERQC) system ensure the integrity of glycoproteins?
What is the primary role of the smooth endoplasmic reticulum?
What is the primary role of the smooth endoplasmic reticulum?
Which process primarily occurs in the rough endoplasmic reticulum?
Which process primarily occurs in the rough endoplasmic reticulum?
Which statement best describes the Golgi apparatus's function within the endomembrane system?
Which statement best describes the Golgi apparatus's function within the endomembrane system?
What is one characteristic feature of the rough endoplasmic reticulum?
What is one characteristic feature of the rough endoplasmic reticulum?
What type of proteins are synthesized in the rough endoplasmic reticulum?
What type of proteins are synthesized in the rough endoplasmic reticulum?
How do transport vesicles function in the endomembrane system?
How do transport vesicles function in the endomembrane system?
What is the internal space of the endoplasmic reticulum called?
What is the internal space of the endoplasmic reticulum called?
Which organelle is continuous with the outer nuclear membrane?
Which organelle is continuous with the outer nuclear membrane?
What happens to the signal sequence in secretory proteins once they are fully translocated across the membrane?
What happens to the signal sequence in secretory proteins once they are fully translocated across the membrane?
In Type I transmembrane proteins, what is the role of the secondary hydrophobic region?
In Type I transmembrane proteins, what is the role of the secondary hydrophobic region?
Which statement correctly describes the orientation of internal signal sequences in Types II and III transmembrane proteins?
Which statement correctly describes the orientation of internal signal sequences in Types II and III transmembrane proteins?
What is the main function of the translocon during protein translocation?
What is the main function of the translocon during protein translocation?
How do multipass transmembrane proteins differ from single-pass proteins?
How do multipass transmembrane proteins differ from single-pass proteins?
Which type of protein is characterized by having a signal sequence targeted to the ER lumen?
Which type of protein is characterized by having a signal sequence targeted to the ER lumen?
What characterizes the movement of transmembrane proteins within the ER membrane?
What characterizes the movement of transmembrane proteins within the ER membrane?
What type of proteins are typically involved in receptor functions within the cell membrane?
What type of proteins are typically involved in receptor functions within the cell membrane?
What is the primary role of the Rough ER in the cell?
What is the primary role of the Rough ER in the cell?
Which type of coated vesicle is responsible for transporting materials from the ER to the Golgi apparatus?
Which type of coated vesicle is responsible for transporting materials from the ER to the Golgi apparatus?
What process allows for the packaging and transport of proteins and lipids received from the ER?
What process allows for the packaging and transport of proteins and lipids received from the ER?
Which statement describes the function of the Golgi apparatus?
Which statement describes the function of the Golgi apparatus?
During which process do COPI-coated vesicles bud off from vesicular tubular clusters?
During which process do COPI-coated vesicles bud off from vesicular tubular clusters?
What role do chaperone proteins play in the endoplasmic reticulum?
What role do chaperone proteins play in the endoplasmic reticulum?
What initiates the transport of a ribosome and polypeptide chain to the ER membrane?
What initiates the transport of a ribosome and polypeptide chain to the ER membrane?
Which network in the Golgi apparatus is tasked with the sorting and distribution of proteins?
Which network in the Golgi apparatus is tasked with the sorting and distribution of proteins?
What is the primary role of endocytosis in cellular function?
What is the primary role of endocytosis in cellular function?
What occurs during the modification of oligosaccharides within the Golgi apparatus?
What occurs during the modification of oligosaccharides within the Golgi apparatus?
What is the primary function of Binding immunoglobulin protein (BiP) in the endoplasmic reticulum?
What is the primary function of Binding immunoglobulin protein (BiP) in the endoplasmic reticulum?
Which statement about N-linked glycosylation in the ER is accurate?
Which statement about N-linked glycosylation in the ER is accurate?
What role does protein disulfide isomerase perform in the ER?
What role does protein disulfide isomerase perform in the ER?
How does BiP respond to incorrectly folded proteins?
How does BiP respond to incorrectly folded proteins?
What is the significance of the ER retention signal found in resident proteins in the ER lumen?
What is the significance of the ER retention signal found in resident proteins in the ER lumen?
What is the primary role of N-linked glycosylation in protein stability?
What is the primary role of N-linked glycosylation in protein stability?
What process occurs when an unfolded protein is not properly folded in the endoplasmic reticulum?
What process occurs when an unfolded protein is not properly folded in the endoplasmic reticulum?
What happens to proteins that exceed the degradation capacity of the endoplasmic reticulum?
What happens to proteins that exceed the degradation capacity of the endoplasmic reticulum?
Which system is responsible for degrading misfolded proteins that cannot be handled by the endoplasmic reticulum?
Which system is responsible for degrading misfolded proteins that cannot be handled by the endoplasmic reticulum?
What is the consequence of ineffective protein folding in the ER?
What is the consequence of ineffective protein folding in the ER?
What is the main role of cholesterol in the cell membrane?
What is the main role of cholesterol in the cell membrane?
Which enzyme in the smooth ER is critical for detoxifying lipid-soluble drugs?
Which enzyme in the smooth ER is critical for detoxifying lipid-soluble drugs?
How does the signal recognition particle (SRP) initiate protein distribution to the ER?
How does the signal recognition particle (SRP) initiate protein distribution to the ER?
What is the specialized function of the sarcoplasmic reticulum in muscle cells?
What is the specialized function of the sarcoplasmic reticulum in muscle cells?
What initiates the process of protein synthesis in the rough ER?
What initiates the process of protein synthesis in the rough ER?
What primary function does the smooth endoplasmic reticulum not perform?
What primary function does the smooth endoplasmic reticulum not perform?
Which correctly describes the internal structure of the endoplasmic reticulum?
Which correctly describes the internal structure of the endoplasmic reticulum?
In what way does the rough endoplasmic reticulum assist in protein processing?
In what way does the rough endoplasmic reticulum assist in protein processing?
What role do ribosomes play in the structure of the rough endoplasmic reticulum?
What role do ribosomes play in the structure of the rough endoplasmic reticulum?
How do transport vesicles facilitate movement between the endoplasmic reticulum and Golgi apparatus?
How do transport vesicles facilitate movement between the endoplasmic reticulum and Golgi apparatus?
Which characteristic distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?
Which characteristic distinguishes smooth endoplasmic reticulum from rough endoplasmic reticulum?
What is a key function of the Golgi apparatus in relation to proteins?
What is a key function of the Golgi apparatus in relation to proteins?
What property of membranes in the endomembrane system is highlighted?
What property of membranes in the endomembrane system is highlighted?
What role does the Rough ER primarily serve in the cell?
What role does the Rough ER primarily serve in the cell?
Which of the following functions is NOT associated with the Smooth ER?
Which of the following functions is NOT associated with the Smooth ER?
What is the role of the signal sequence in transmembrane proteins?
What is the role of the signal sequence in transmembrane proteins?
What type of coated vesicle is chiefly responsible for transport from the ER to the Golgi apparatus?
What type of coated vesicle is chiefly responsible for transport from the ER to the Golgi apparatus?
In the context of transmembrane proteins, what is a 'Stop Transfer Signal'?
In the context of transmembrane proteins, what is a 'Stop Transfer Signal'?
In the Golgi apparatus, what is the primary function of the Trans Golgi network?
In the Golgi apparatus, what is the primary function of the Trans Golgi network?
Which component aids in the transport of vesicles along microtubules towards the Golgi apparatus?
Which component aids in the transport of vesicles along microtubules towards the Golgi apparatus?
What distinguishes Types II and III transmembrane proteins from Type I?
What distinguishes Types II and III transmembrane proteins from Type I?
How are multipass transmembrane proteins structured?
How are multipass transmembrane proteins structured?
What is the process by which nutrients are internalized by the cell called?
What is the process by which nutrients are internalized by the cell called?
What does the term 'cis Golgi network' refer to in the context of the Golgi apparatus?
What does the term 'cis Golgi network' refer to in the context of the Golgi apparatus?
Which process includes the fusion of ER-derived vesicles to form vesicular tubular clusters?
Which process includes the fusion of ER-derived vesicles to form vesicular tubular clusters?
What initiates the binding of the SRP-ribosome complex to the ER membrane?
What initiates the binding of the SRP-ribosome complex to the ER membrane?
Which of the following statements is TRUE regarding internal signal sequences?
Which of the following statements is TRUE regarding internal signal sequences?
What modification process occurs to proteins within the Golgi apparatus?
What modification process occurs to proteins within the Golgi apparatus?
How do transmembrane proteins move laterally within the membrane?
How do transmembrane proteins move laterally within the membrane?
What is one of the roles of cholesterol in cellular membranes?
What is one of the roles of cholesterol in cellular membranes?
Which enzyme is associated with drug detoxification in the Smooth ER?
Which enzyme is associated with drug detoxification in the Smooth ER?
What characterizes the rough endoplasmic reticulum?
What characterizes the rough endoplasmic reticulum?
What does the signal recognition particle (SRP) bind to during protein distribution to the ER?
What does the signal recognition particle (SRP) bind to during protein distribution to the ER?
Which of the following is a function of the smooth endoplasmic reticulum?
Which of the following is a function of the smooth endoplasmic reticulum?
How are transport vesicles primarily involved in the endomembrane system?
How are transport vesicles primarily involved in the endomembrane system?
What is the primary internal space of the endoplasmic reticulum known as?
What is the primary internal space of the endoplasmic reticulum known as?
Which of these membrane-bound organelles is part of the endomembrane system?
Which of these membrane-bound organelles is part of the endomembrane system?
What is one of the metabolic functions of the rough endoplasmic reticulum?
What is one of the metabolic functions of the rough endoplasmic reticulum?
What do the membranes within the endomembrane system have in common?
What do the membranes within the endomembrane system have in common?
What form of proteins does the rough endoplasmic reticulum primarily synthesize?
What form of proteins does the rough endoplasmic reticulum primarily synthesize?
What role does BiP chaperone protein play in the endoplasmic reticulum?
What role does BiP chaperone protein play in the endoplasmic reticulum?
What is the primary function of protein disulfide isomerase in the endoplasmic reticulum?
What is the primary function of protein disulfide isomerase in the endoplasmic reticulum?
What percentage of glycoproteins undergo N-linked glycosylation in the endoplasmic reticulum?
What percentage of glycoproteins undergo N-linked glycosylation in the endoplasmic reticulum?
How do molecular chaperones in the ER assist with protein folding?
How do molecular chaperones in the ER assist with protein folding?
What is the primary signal for retention of resident proteins in the ER lumen?
What is the primary signal for retention of resident proteins in the ER lumen?
What role does N-linked glycosylation play in protein stability?
What role does N-linked glycosylation play in protein stability?
What happens to proteins that do not achieve their fully folded state in the ER?
What happens to proteins that do not achieve their fully folded state in the ER?
What is the function of chaperone proteins in the context of N-linked glycosylation?
What is the function of chaperone proteins in the context of N-linked glycosylation?
What initiates the unfolded protein response in the ER?
What initiates the unfolded protein response in the ER?
During the glycosylation process, which sugars are trimmed before the protein is transported to the Golgi?
During the glycosylation process, which sugars are trimmed before the protein is transported to the Golgi?
What directs the ribosome and polypeptide chain to the ER membrane?
What directs the ribosome and polypeptide chain to the ER membrane?
What type of coated vesicle mediates transport from the ER to the Golgi?
What type of coated vesicle mediates transport from the ER to the Golgi?
Which function is NOT associated with the Smooth ER?
Which function is NOT associated with the Smooth ER?
What is the purpose of vesicular tubular clusters?
What is the purpose of vesicular tubular clusters?
What is one of the roles of the Golgi apparatus?
What is one of the roles of the Golgi apparatus?
What is the role of the trans Golgi network?
What is the role of the trans Golgi network?
Which process is responsible for internalization of nutrients?
Which process is responsible for internalization of nutrients?
Which of the following is true regarding N-linked glycosylation?
Which of the following is true regarding N-linked glycosylation?
How do COPI-coated vesicles function within the Golgi?
How do COPI-coated vesicles function within the Golgi?
What happens to the signal sequence after protein synthesis for secretory proteins?
What happens to the signal sequence after protein synthesis for secretory proteins?
Which characteristic differentiates Type I transmembrane proteins from Types II and III?
Which characteristic differentiates Type I transmembrane proteins from Types II and III?
What does the 'Stop Transfer Signal' do during protein translocation?
What does the 'Stop Transfer Signal' do during protein translocation?
Which statement is true about the orientation of internal signal sequences in Types II and III transmembrane proteins?
Which statement is true about the orientation of internal signal sequences in Types II and III transmembrane proteins?
What is the function of the translocon during protein synthesis?
What is the function of the translocon during protein synthesis?
In multipass transmembrane proteins, what is the role of alternating internal signal sequences and stop transfer signals?
In multipass transmembrane proteins, what is the role of alternating internal signal sequences and stop transfer signals?
Which type of proteins are characterized by having an internal signal sequence that can orient either way through the translocon?
Which type of proteins are characterized by having an internal signal sequence that can orient either way through the translocon?
What role does the SRP-ribosome complex play in protein synthesis?
What role does the SRP-ribosome complex play in protein synthesis?
Flashcards
Endoplasmic Reticulum (ER)
Endoplasmic Reticulum (ER)
A network of interconnected membrane-enclosed sacs and tubules found within eukaryotic cells.
Rough ER
Rough ER
A type of ER studded with ribosomes, responsible for protein synthesis and modification.
Smooth ER
Smooth ER
A type of ER lacking ribosomes, involved in lipid synthesis, detoxification, and calcium storage.
Endomembrane System
Endomembrane System
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ER to Golgi Transport
ER to Golgi Transport
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Golgi Apparatus
Golgi Apparatus
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ER Lumen
ER Lumen
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Removal of Incorrect Proteins
Removal of Incorrect Proteins
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Phospholipids
Phospholipids
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Cholesterol
Cholesterol
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Protein Translocation
Protein Translocation
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BiP (Binding Immunoglobulin Protein)
BiP (Binding Immunoglobulin Protein)
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Disulfide Bond Formation
Disulfide Bond Formation
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N-linked Glycosylation
N-linked Glycosylation
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ER Retention Signal
ER Retention Signal
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What is ER Quality Control (ERQC)?
What is ER Quality Control (ERQC)?
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What is the ubiquitin-proteasome system?
What is the ubiquitin-proteasome system?
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What is the autophagic-lysosomal system?
What is the autophagic-lysosomal system?
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What is the unfolded protein response (UPR)?
What is the unfolded protein response (UPR)?
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What is ER stress?
What is ER stress?
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SRP-ribosome complex binding
SRP-ribosome complex binding
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Signal sequence enters the translocon
Signal sequence enters the translocon
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Polypeptide chain translocation
Polypeptide chain translocation
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Secretory protein translocation
Secretory protein translocation
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Type I transmembrane protein
Type I transmembrane protein
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Type II/III transmembrane proteins
Type II/III transmembrane proteins
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Multipass transmembrane protein
Multipass transmembrane protein
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Internal signal sequence orientation
Internal signal sequence orientation
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COPII-coated vesicle
COPII-coated vesicle
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Chaperone proteins
Chaperone proteins
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COPI-coated vesicles
COPI-coated vesicles
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Cis Golgi network
Cis Golgi network
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Golgi stack
Golgi stack
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Trans Golgi network
Trans Golgi network
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Study Notes
Endoplasmic Reticulum (ER) and Golgi Apparatus
- The endoplasmic reticulum (ER) and Golgi apparatus are part of the endomembrane system.
- The ER and Golgi are involved in protein and lipid synthesis, modification, and transport.
- Membranes within these organelles are not identical and are dynamic in nature.
- The ER constitutes more than half of the total membrane in an average animal cell.
Endoplasmic Reticulum (ER)
-
Structure: The ER is a labyrinth of branching interconnected tubules and sacs continuous with the outer nuclear membrane. The single internal space is the ER lumen. There are two types: Rough ER and Smooth ER.
-
Rough ER: Composed of flattened sheets with ribosomes attached to the cytosolic surface. These ribosomes synthesize proteins.
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Smooth ER: Consists of tubular structures with no ribosomes. It plays a role in lipid synthesis, carbohydrate metabolism, calcium storage, and detoxification.
ER Function
- Smooth ER: Lipid biosynthesis (oils, steroids, phospholipids), carbohydrate metabolism, calcium storage, detoxification of drugs and poisons. Cholesterol is an important component in membrane structure and plays a role in bile and steroid synthesis.
- Rough ER: Protein biosynthesis (water-soluble secretory proteins, transmembrane proteins), protein folding and modification, protein quality control (removal of incorrect proteins).
Rough ER: Protein Biosynthesis
- Ribosomes in the cytoplasm bind to mRNA at initiation of protein synthesis.
- Proteins with an amino acid signal sequence are directed to the ER.
- Signal recognition particle (SRP) binds to the signal sequence, stopping translation temporarily.
- SRP-ribosome complex binds to SRP receptor (on ER membrane) and the translocation complex (Sec61).
- Polypeptide chain enters the translocon, and translation resumes.
- Signal sequence is cleaved, and the protein is completely translocated across the membrane.
- For transmembrane proteins, stopping transfer signals determine the location and orientation of the polypeptide chain in the membrane.
Transmembrane Proteins
- Type I: Single pass – N-terminus signal sequence targeted to ER lumen, and a second hydrophobic region (Stop transfer signal) halts insertion and forms a single-pass transmembrane protein.
- Types II/III: Single pass – internal signal sequences can be oriented either carboxyl or amino terminus in the cytosol (No signal sequence at N-terminus); one internal hydrophobic region insertion/orientation determines formation of a single-pass protein.
- Multipass: Multiple alternating internal signal sequences determine the locations and orientations to form multipass transmembrane proteins.
Protein Folding
- ER: The ER plays a crucial role in protein folding.
- Molecular chaperones and folding enzymes in the ER lumen assist in protein folding and control subsequent release.
Protein Folding by ER Chaperones
- BIP (Binding immunoglobulin protein) is a chaperone protein that binds to polypeptide chains and drives unidirectional translocation, aiding protein folding and preventing aggregation of proteins.
- It detects incorrectly folded proteins by binding to exposed amino acids and prevents them from exiting the ER.
Protein Folding: Disulfide Bond Formation
- Protein disulfide isomerase within the ER lumen catalyzes the oxidation of sulfhydryl groups on cysteine residues to form disulfide bonds, which are important for stabilizing protein structure.
N-linked glycosylation
- N-linked glycosylation is the addition of a pre-formed oligosaccharide (14 sugars) to asparagine side chain NHâ‚‚ groups on around 90% of ER-processed glycoproteins.
- This process stabilizes proteins by masking hydrophobic regions, preventing degradation, and increasing protein solubility.
ER Quality Control
- The ER is responsible for protein quality control. Very few proteins achieve their fully folded state.
- The build-up of misfolded, damaged proteins causes ER stress.
- Two systems help with degradation of proteins:
- Ubiquitin–proteasome system: misfolded proteins are translocated to the cytosol and tagged with ubiquitin, then degraded.
- Autophagic–lysosomal system: aberrant protein fragments are degraded by lysosomes.
Golgi Apparatus
- The Golgi apparatus is a series of membranous sacs (cisternae). The Golgi receives proteins and lipids from the ER, modifies them further, and sorts them for eventual destinations (e.g., plasma membrane, lysosomes, secretory vesicles).
- The Golgi has different sections that perform different tasks.
- Cis Golgi network: Beginning of modification (sorting and receiving); protein, lipid, polysaccharide modification begins.
- Golgi stack: Modification continues.
- Trans Golgi network: Final modifications and sorting for different destinations; protein sorting to different destinations.
Processing in Golgi
- Enzymes in the Golgi cisternae (in specific steps) perform specific modifications of protein and lipids. This may include: addition/removal of sugars (oligosaccharide processing), phosphorylation, or sulfation.
Transport Mechanisms
- Endocytosis: Bringing materials into the cell.
- Exocytosis: Moving materials out of the cell.
- Transport vesicles: Membrane-enclosed structures used to transport cargo between compartments—COPI, COPII, and clathrin-coated vesicles.
Vesicular transport / Tubular clusters
- ER-derived COPII vesicles bind to COPI coated transport vesicles and fuse to form Vesicular Tubular clusters, which move on microtubules toward the Golgi apparatus.
- COPI coated transport vesicles then bud off, carrying resident proteins back to the ER.
- Vesicular tubular clusters continually mature as they move.
ER Summary
- ER is part of the endomembrane system and is continuous with the nuclear envelope.
- It produces proteins and lipids.
- Rough ER primarily synthesizes secretory or transmembrane proteins.
- Smooth ER handles diverse metabolic functions (lipid synthesis, carbohydrate metabolism, calcium storage, and detoxification.)
- Signal sequences and signal recognition particle guide proteins to the ER membrane.
- Chaperone proteins and enzymes help with protein folding and ensure quality control within the ER lumen.
- N-linked glycosylation plays a role in protein folding and stability.
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Test your knowledge on cell biology and the functions of the endoplasmic reticulum. This quiz covers key concepts including cholesterol's role in cellular permeability, the function of chaperones, protein synthesis, and the endomembrane system. Perfect for students studying cell biology at any level.
