10 Questions
Which organelle is responsible for protein sorting in the cell?
Endoplasmic reticulum
Which of the following proteins is NOT bound to go to the rough endoplasmic reticulum (rER)?
Lysosome enzymes
What is the function of the signal sequence on a protein?
Bind to docking sites on the ER membrane
What happens if a protein has a stop-transfer signal on its ER membrane protein?
It is retained in the ER
What happens to the signal sequence on a protein after it is inserted into the ER?
It is retained as part of the protein
Which of the following proteins is NOT bound to go to the rough endoplasmic reticulum (rER)?
Lysosome enzymes
Where is the synthesis of ER proteins initiated?
On a ribosome in the cytoplasm
What directs the insertion of nascent proteins into or across the ER membrane?
Signal Recognition Particle (SRP)
What happens to the signal sequence on a protein after it is inserted into the ER?
It is clipped off
What determines whether a protein goes into the ER or not if it does not have a stop-transfer signal on its ER membrane protein?
The presence of a signal sequence
Study Notes
Protein Sorting and Synthesis
- The organelle responsible for protein sorting in the cell is the rough endoplasmic reticulum (rER).
- The protein that is NOT bound to go to the rER is the one that doesn't have a signal sequence.
- The signal sequence on a protein directs the protein to the rER for synthesis and insertion into the ER membrane.
- If a protein has a stop-transfer signal on its ER membrane protein, it will be anchored to the ER membrane.
- After a protein is inserted into the ER, the signal sequence is removed.
- Proteins that are synthesized in the rER have their synthesis initiated in the ribosomes.
- The signal recognition particle (SRP) directs the insertion of nascent proteins into or across the ER membrane.
- The presence or absence of a signal sequence determines whether a protein goes into the ER or not.
Test your knowledge on intracellular compartments and protein sorting with this quiz based on Chapter 12 and 13 of the Molecular Biology of the Cell Sixth Edition. Learn about the signal sequences and the proteins bound to the rough endoplasmic reticulum (rER).
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