Podcast
Questions and Answers
The smooth endoplasmic reticulum (SER) is devoid of ribosomes.
The smooth endoplasmic reticulum (SER) is devoid of ribosomes.
True
The endomembrane system is present in prokaryotic cells.
The endomembrane system is present in prokaryotic cells.
False
The ER membrane is thicker than the plasma membrane.
The ER membrane is thicker than the plasma membrane.
False
Rough microsomes can be separated from smooth microsomes by centrifugation in a sucrose density gradient.
Rough microsomes can be separated from smooth microsomes by centrifugation in a sucrose density gradient.
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The ER is linked to the nuclear envelope.
The ER is linked to the nuclear envelope.
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The plant vacuole is not part of the endomembrane system.
The plant vacuole is not part of the endomembrane system.
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Protein synthesis always begins in the cytosol with initiation and the start of elongation. True or False?
Protein synthesis always begins in the cytosol with initiation and the start of elongation. True or False?
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The signal sequence consists of the first hydrophobic amino acids located at the C-terminus of the protein. True or False?
The signal sequence consists of the first hydrophobic amino acids located at the C-terminus of the protein. True or False?
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The Signal Recognition Particle (SRP) binds to the signal sequence and causes a temporary halt in translation. True or False?
The Signal Recognition Particle (SRP) binds to the signal sequence and causes a temporary halt in translation. True or False?
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The translocon opens up via a hydrophobic channel, allowing the protein being synthesized to be translocated into the lumen of the RER. True or False?
The translocon opens up via a hydrophobic channel, allowing the protein being synthesized to be translocated into the lumen of the RER. True or False?
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When the protein enters the lumen of the RER, a signal peptidase located on the luminal side of the RER membrane cuts the signal sequence. True or False?
When the protein enters the lumen of the RER, a signal peptidase located on the luminal side of the RER membrane cuts the signal sequence. True or False?
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The protein released into the lumen of the RER is a luminal protein. True or False?
The protein released into the lumen of the RER is a luminal protein. True or False?
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The smooth microsomes in a sucrose concentration gradient separate them according to their color and origin. True or False?
The smooth microsomes in a sucrose concentration gradient separate them according to their color and origin. True or False?
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The membrane contains around 50% protein and 50% lipids. True or False?
The membrane contains around 50% protein and 50% lipids. True or False?
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Cholesterol is present in large quantities in the membrane. True or False?
Cholesterol is present in large quantities in the membrane. True or False?
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A large percentage of carbohydrates are attached to proteins and lipids and are found towards the cytosolic surface. True or False?
A large percentage of carbohydrates are attached to proteins and lipids and are found towards the cytosolic surface. True or False?
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Study Notes
Endoplasmic Reticulum (ER)
- The smooth endoplasmic reticulum (SER) lacks ribosomes.
- The ER membrane is thicker than the plasma membrane.
Separation of Microsomes
- Rough microsomes can be separated from smooth microsomes by centrifugation in a sucrose density gradient.
ER-Nuclear Envelope Link
- The ER is linked to the nuclear envelope.
Endomembrane System
- The plant vacuole is not part of the endomembrane system.
- The endomembrane system is not present in prokaryotic cells.
Protein Synthesis
- Protein synthesis begins in the cytosol with initiation and start of elongation.
Signal Sequence and SRP
- The signal sequence consists of the first hydrophobic amino acids located at the N-terminus of the protein.
- The Signal Recognition Particle (SRP) binds to the signal sequence, causing a temporary halt in translation.
Protein Translocation
- The translocon opens up via a hydrophobic channel, allowing the protein being synthesized to be translocated into the lumen of the RER.
- A signal peptidase located on the luminal side of the RER membrane cuts the signal sequence when the protein enters the lumen of the RER.
Lumenal Protein
- The protein released into the lumen of the RER is a luminal protein.
Microsome Separation
- Smooth microsomes do not separate according to their color and origin in a sucrose concentration gradient.
Membrane Composition
- The membrane contains approximately 50% protein and 50% lipids.
- Cholesterol is present in large quantities in the membrane.
- A large percentage of carbohydrates are attached to proteins and lipids and are found towards the cytosolic surface.
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Description
Test your knowledge of the endomembrane system in eukaryotic cells, including the endoplasmic reticulum, Golgi apparatus, phagosomes, endosomes, lysosomes, and plant vacuoles. Explore the definitions and functions of each component within this essential biological system.
